A better looking and faster spot shadow.

1. This improve the looking, the star shape (spike) on long action bar is gone.
Shadow is more smooth now.

2. The performance is better, too. For averaging around rect, round rect and
circle, the spot shadow itself is 3 times faster. On N7 v1, it could be less than
0.1 ms.

b/14976551
b/16712006

Change-Id: I61ed546ee56e7c8dbe504dfcaef12d084904b4b8

1 files changed, 296 insertions, 614 deletions

diff --git a/libs/hwui/SpotShadow.cpp b/libs/hwui/SpotShadow.cpp
index df28ae8..e8f1b9a 100644
--- a/libs/hwui/SpotShadow.cpp
+++ b/libs/hwui/SpotShadow.cpp
@@ -618,68 +618,6 @@ void SpotShadow::createSpotShadow(bool isCasterOpaque, const Vector3& lightCente
 }
 
 /**
- * Converts a polygon specified with CW vertices into an array of distance-from-centroid values.
- *
- * Returns false in error conditions
- *
- * @param poly Array of vertices. Note that these *must* be CW.
- * @param polyLength The number of vertices in the polygon.
- * @param polyCentroid The centroid of the polygon, from which rays will be cast
- * @param rayDist The output array for the calculated distances, must be SHADOW_RAY_COUNT in size
- */
-bool convertPolyToRayDist(const Vector2* poly, int polyLength, const Vector2& polyCentroid,
-        float* rayDist) {
-    const int rays = SHADOW_RAY_COUNT;
-    const float step = M_PI * 2 / rays;
-
-    const Vector2* lastVertex = &(poly[polyLength - 1]);
-    float startAngle = angle(*lastVertex, polyCentroid);
-
-    // Start with the ray that's closest to and less than startAngle
-    int rayIndex = floor((startAngle - EPSILON) / step);
-    rayIndex = (rayIndex + rays) % rays; // ensure positive
-
-    for (int polyIndex = 0; polyIndex < polyLength; polyIndex++) {
-        /*
-         * For a given pair of vertices on the polygon, poly[i-1] and poly[i], the rays that
-         * intersect these will be those that are between the two angles from the centroid that the
-         * vertices define.
-         *
-         * Because the polygon vertices are stored clockwise, the closest ray with an angle
-         * *smaller* than that defined by angle(poly[i], centroid) will be the first ray that does
-         * not intersect with poly[i-1], poly[i].
-         */
-        float currentAngle = angle(poly[polyIndex], polyCentroid);
-
-        // find first ray that will not intersect the line segment poly[i-1] & poly[i]
-        int firstRayIndexOnNextSegment = floor((currentAngle - EPSILON) / step);
-        firstRayIndexOnNextSegment = (firstRayIndexOnNextSegment + rays) % rays; // ensure positive
-
-        // Iterate through all rays that intersect with poly[i-1], poly[i] line segment.
-        // This may be 0 rays.
-        while (rayIndex != firstRayIndexOnNextSegment) {
-            float distanceToIntersect = rayIntersectPoints(polyCentroid,
-                    cos(rayIndex * step),
-                    sin(rayIndex * step),
-                    *lastVertex, poly[polyIndex]);
-            if (distanceToIntersect < 0) {
-#if DEBUG_SHADOW
-                ALOGW("ERROR: convertPolyToRayDist failed");
-#endif
-                return false; // error case, abort
-            }
-
-            rayDist[rayIndex] = distanceToIntersect;
-
-            rayIndex = (rayIndex - 1 + rays) % rays;
-        }
-        lastVertex = &poly[polyIndex];
-    }
-
-    return true;
-}
-
-/**
  * This is only for experimental purpose.
  * After intersections are calculated, we could smooth the polygon if needed.
  * So far, we don't think it is more appealing yet.
@@ -700,490 +638,223 @@ void SpotShadow::smoothPolygon(int level, int rays, float* rayDist) {
     }
 }
 
-/**
- * Generate a array of the angleData for either umbra or penumbra vertices.
- *
- * This array will be merged and used to guide where to shoot the rays, in clockwise order.
- *
- * @param angleDataList The result array of angle data.
- *
- * @return int The maximum angle's index in the array.
- */
-int SpotShadow::setupAngleList(VertexAngleData* angleDataList,
-        int polyLength, const Vector2* polygon, const Vector2& centroid,
-        bool isPenumbra, const char* name) {
-    float maxAngle = FLT_MIN;
-    int maxAngleIndex = 0;
-    for (int i = 0; i < polyLength; i++) {
-        float currentAngle = angle(polygon[i], centroid);
-        if (currentAngle > maxAngle) {
-            maxAngle = currentAngle;
-            maxAngleIndex = i;
-        }
-        angleDataList[i].set(currentAngle, isPenumbra, i);
-#if DEBUG_SHADOW
-        ALOGD("%s AngleList i %d %f", name, i, currentAngle);
-#endif
-    }
-    return maxAngleIndex;
-}
+// Index pair is meant for storing the tessellation information for the penumbra
+// area. One index must come from exterior tangent of the circles, the other one
+// must come from the interior tangent of the circles.
+struct IndexPair {
+    int outerIndex;
+    int innerIndex;
+};
 
-/**
- * Make sure the polygons are indeed in clockwise order.
- *
- * Possible reasons to return false: 1. The input polygon is not setup properly. 2. The hull
- * algorithm is not able to generate it properly.
- *
- * Anyway, since the algorithm depends on the clockwise, when these kind of unexpected error
- * situation is found, we need to detect it and early return without corrupting the memory.
- *
- * @return bool True if the angle list is actually from big to small.
- */
-bool SpotShadow::checkClockwise(int indexOfMaxAngle, int listLength, VertexAngleData* angleList,
-        const char* name) {
-    int currentIndex = indexOfMaxAngle;
-#if DEBUG_SHADOW
-    ALOGD("max index %d", currentIndex);
-#endif
-    for (int i = 0; i < listLength - 1; i++) {
-        // TODO: Cache the last angle.
-        float currentAngle = angleList[currentIndex].mAngle;
-        float nextAngle = angleList[(currentIndex + 1) % listLength].mAngle;
-        if (currentAngle < nextAngle) {
-#if DEBUG_SHADOW
-            ALOGE("%s, is not CW, at index %d", name, currentIndex);
-#endif
-            return false;
+// For one penumbra vertex, find the cloest umbra vertex and return its index.
+inline int getClosestUmbraIndex(const Vector2& pivot, const Vector2* polygon, int polygonLength) {
+    float minLengthSquared = FLT_MAX;
+    int resultIndex = -1;
+    bool hasDecreased = false;
+    // Starting with some negative offset, assuming both umbra and penumbra are starting
+    // at the same angle, this can help to find the result faster.
+    // Normally, loop 3 times, we can find the closest point.
+    int offset = polygonLength - 2;
+    for (int i = 0; i < polygonLength; i++) {
+        int currentIndex = (i + offset) % polygonLength;
+        float currentLengthSquared = (pivot - polygon[currentIndex]).lengthSquared();
+        if (currentLengthSquared < minLengthSquared) {
+            if (minLengthSquared != FLT_MAX) {
+                hasDecreased = true;
+            }
+            minLengthSquared = currentLengthSquared;
+            resultIndex = currentIndex;
+        } else if (currentLengthSquared > minLengthSquared && hasDecreased) {
+            // Early break b/c we have found the closet one and now the length
+            // is increasing again.
+            break;
         }
-        currentIndex = (currentIndex + 1) % listLength;
     }
-    return true;
+    if(resultIndex == -1) {
+        ALOGE("resultIndex is -1, the polygon must be invalid!");
+        resultIndex = 0;
+    }
+    return resultIndex;
 }
 
-/**
- * Check the polygon is clockwise.
- *
- * @return bool True is the polygon is clockwise.
- */
-bool SpotShadow::checkPolyClockwise(int polyAngleLength, int maxPolyAngleIndex,
-        const float* polyAngleList) {
-    bool isPolyCW = true;
-    // Starting from maxPolyAngleIndex , check around to make sure angle decrease.
-    for (int i = 0; i < polyAngleLength - 1; i++) {
-        float currentAngle = polyAngleList[(i + maxPolyAngleIndex) % polyAngleLength];
-        float nextAngle = polyAngleList[(i + maxPolyAngleIndex + 1) % polyAngleLength];
-        if (currentAngle < nextAngle) {
-            isPolyCW = false;
-        }
+inline bool sameDirections(bool isPositiveCross, float a, float b) {
+    if (isPositiveCross) {
+        return a >= 0 && b >= 0;
+    } else {
+        return a <= 0 && b <= 0;
     }
-    return isPolyCW;
 }
 
-/**
- * Given the sorted array of all the vertices angle data, calculate for each
- * vertices, the offset value to array element which represent the start edge
- * of the polygon we need to shoot the ray at.
- *
- * TODO: Calculate this for umbra and penumbra in one loop using one single array.
- *
- * @param distances The result of the array distance counter.
- */
-void SpotShadow::calculateDistanceCounter(bool needsOffsetToUmbra, int angleLength,
-        const VertexAngleData* allVerticesAngleData, int* distances) {
-
-    bool firstVertexIsPenumbra = allVerticesAngleData[0].mIsPenumbra;
-    // If we want distance to inner, then we just set to 0 when we see inner.
-    bool needsSearch = needsOffsetToUmbra ? firstVertexIsPenumbra : !firstVertexIsPenumbra;
-    int distanceCounter = 0;
-    if (needsSearch) {
-        int foundIndex = -1;
-        for (int i = (angleLength - 1); i >= 0; i--) {
-            bool currentIsOuter = allVerticesAngleData[i].mIsPenumbra;
-            // If we need distance to inner, then we need to find a inner vertex.
-            if (currentIsOuter != firstVertexIsPenumbra) {
-                foundIndex = i;
-                break;
-            }
-        }
-        LOG_ALWAYS_FATAL_IF(foundIndex == -1, "Wrong index found, means either"
-                " umbra or penumbra's length is 0");
-        distanceCounter = angleLength - foundIndex;
-    }
+// Find the right polygon edge to shoot the ray at.
+inline int findPolyIndex(bool isPositiveCross, int startPolyIndex, const Vector2& umbraDir,
+        const Vector2* polyToCentroid, int polyLength) {
+    // Make sure we loop with a bound.
+    for (int i = 0; i < polyLength; i++) {
+        int currentIndex = (i + startPolyIndex) % polyLength;
+        const Vector2& currentToCentroid = polyToCentroid[currentIndex];
+        const Vector2& nextToCentroid = polyToCentroid[(currentIndex + 1) % polyLength];
+
+        float currentCrossUmbra = currentToCentroid.cross(umbraDir);
+        float umbraCrossNext = umbraDir.cross(nextToCentroid);
+        if (sameDirections(isPositiveCross, currentCrossUmbra, umbraCrossNext)) {
 #if DEBUG_SHADOW
-    ALOGD("distances[0] is %d", distanceCounter);
+            ALOGD("findPolyIndex loop %d times , index %d", i, currentIndex );
 #endif
-
-    distances[0] = distanceCounter; // means never see a target poly
-
-    for (int i = 1; i < angleLength; i++) {
-        bool firstVertexIsPenumbra = allVerticesAngleData[i].mIsPenumbra;
-        // When we needs for distance for each outer vertex to inner, then we
-        // increase the distance when seeing outer vertices. Otherwise, we clear
-        // to 0.
-        bool needsIncrement = needsOffsetToUmbra ? firstVertexIsPenumbra : !firstVertexIsPenumbra;
-        // If counter is not -1, that means we have seen an other polygon's vertex.
-        if (needsIncrement && distanceCounter != -1) {
-            distanceCounter++;
-        } else {
-            distanceCounter = 0;
+            return currentIndex;
         }
-        distances[i] = distanceCounter;
     }
+    LOG_ALWAYS_FATAL("Can't find the right polygon's edge from startPolyIndex %d", startPolyIndex);
+    return -1;
 }
 
-/**
- * Given umbra and penumbra angle data list, merge them by sorting the angle
- * from the biggest to smallest.
- *
- * @param allVerticesAngleData The result array of merged angle data.
- */
-void SpotShadow::mergeAngleList(int maxUmbraAngleIndex, int maxPenumbraAngleIndex,
-        const VertexAngleData* umbraAngleList, int umbraLength,
-        const VertexAngleData* penumbraAngleList, int penumbraLength,
-        VertexAngleData* allVerticesAngleData) {
-
-    int totalRayNumber = umbraLength + penumbraLength;
-    int umbraIndex = maxUmbraAngleIndex;
-    int penumbraIndex = maxPenumbraAngleIndex;
-
-    float currentUmbraAngle = umbraAngleList[umbraIndex].mAngle;
-    float currentPenumbraAngle = penumbraAngleList[penumbraIndex].mAngle;
-
-    // TODO: Clean this up using a while loop with 2 iterators.
-    for (int i = 0; i < totalRayNumber; i++) {
-        if (currentUmbraAngle > currentPenumbraAngle) {
-            allVerticesAngleData[i] = umbraAngleList[umbraIndex];
-            umbraIndex = (umbraIndex + 1) % umbraLength;
-
-            // If umbraIndex round back, that means we are running out of
-            // umbra vertices to merge, so just copy all the penumbra leftover.
-            // Otherwise, we update the currentUmbraAngle.
-            if (umbraIndex != maxUmbraAngleIndex) {
-                currentUmbraAngle = umbraAngleList[umbraIndex].mAngle;
-            } else {
-                for (int j = i + 1; j < totalRayNumber; j++) {
-                    allVerticesAngleData[j] = penumbraAngleList[penumbraIndex];
-                    penumbraIndex = (penumbraIndex + 1) % penumbraLength;
-                }
+// Generate the index pair for penumbra / umbra vertices, and more penumbra vertices
+// if needed.
+inline void genNewPenumbraAndPairWithUmbra(const Vector2* penumbra, int penumbraLength,
+        const Vector2* umbra, int umbraLength, Vector2* newPenumbra, int& newPenumbraIndex,
+        IndexPair* verticesPair, int& verticesPairIndex) {
+    // In order to keep everything in just one loop, we need to pre-compute the
+    // closest umbra vertex for the last penumbra vertex.
+    int previousClosestUmbraIndex = getClosestUmbraIndex(penumbra[penumbraLength - 1],
+            umbra, umbraLength);
+    for (int i = 0; i < penumbraLength; i++) {
+        const Vector2& currentPenumbraVertex = penumbra[i];
+        // For current penumbra vertex, starting from previousClosestUmbraIndex,
+        // then check the next one until the distance increase.
+        // The last one before the increase is the umbra vertex we need to pair with.
+        int currentUmbraIndex = previousClosestUmbraIndex;
+        float currentLengthSquared = (currentPenumbraVertex - umbra[currentUmbraIndex]).lengthSquared();
+        int currentClosestUmbraIndex = -1;
+        int indexDelta = 0;
+        for (int j = 1; j < umbraLength; j++) {
+            int newUmbraIndex = (previousClosestUmbraIndex + j) % umbraLength;
+            float newLengthSquared = (currentPenumbraVertex - umbra[newUmbraIndex]).lengthSquared();
+            if (newLengthSquared > currentLengthSquared) {
+                currentClosestUmbraIndex = (previousClosestUmbraIndex + j - 1) % umbraLength;
                 break;
-            }
-        } else {
-            allVerticesAngleData[i] = penumbraAngleList[penumbraIndex];
-            penumbraIndex = (penumbraIndex + 1) % penumbraLength;
-            // If penumbraIndex round back, that means we are running out of
-            // penumbra vertices to merge, so just copy all the umbra leftover.
-            // Otherwise, we update the currentPenumbraAngle.
-            if (penumbraIndex != maxPenumbraAngleIndex) {
-                currentPenumbraAngle = penumbraAngleList[penumbraIndex].mAngle;
             } else {
-                for (int j = i + 1; j < totalRayNumber; j++) {
-                    allVerticesAngleData[j] = umbraAngleList[umbraIndex];
-                    umbraIndex = (umbraIndex + 1) % umbraLength;
-                }
-                break;
+                currentLengthSquared = newLengthSquared;
+                indexDelta++;
             }
         }
-    }
-}
-
-#if DEBUG_SHADOW
-/**
- * DEBUG ONLY: Verify all the offset compuation is correctly done by examining
- * each vertex and its neighbor.
- */
-static void verifyDistanceCounter(const VertexAngleData* allVerticesAngleData,
-        const int* distances, int angleLength, const char* name) {
-    int currentDistance = distances[0];
-    for (int i = 1; i < angleLength; i++) {
-        if (distances[i] != INT_MIN) {
-            if (!((currentDistance + 1) == distances[i]
-                || distances[i] == 0)) {
-                ALOGE("Wrong distance found at i %d name %s", i, name);
+        LOG_ALWAYS_FATAL_IF(currentClosestUmbraIndex == -1, "Can't find a closet umbra vertext at all");
+
+        if (indexDelta > 1) {
+            // For those umbra don't have  penumbra, generate new penumbra vertices by interpolation.
+            //
+            // Assuming Pi for penumbra vertices, and Ui for umbra vertices.
+            // In the case like below P1 paired with U1 and P2 paired with  U5.
+            // U2 to U4 are unpaired umbra vertices.
+            //
+            // P1                                        P2
+            // |                                          |
+            // U1     U2                   U3     U4     U5
+            //
+            // We will need to generate 3 more penumbra vertices P1.1, P1.2, P1.3
+            // to pair with U2 to U4.
+            //
+            // P1     P1.1                P1.2   P1.3    P2
+            // |       |                   |      |      |
+            // U1     U2                   U3     U4     U5
+            //
+            // That distance ratio b/t Ui to U1 and Ui to U5 decides its paired penumbra
+            // vertex's location.
+            int newPenumbraNumber = indexDelta - 1;
+
+            float accumulatedDeltaLength[newPenumbraNumber];
+            float totalDeltaLength = 0;
+
+            // To save time, cache the previous umbra vertex info outside the loop
+            // and update each loop.
+            Vector2 previousClosestUmbra = umbra[previousClosestUmbraIndex];
+            Vector2 skippedUmbra;
+            // Use umbra data to precompute the length b/t unpaired umbra vertices,
+            // and its ratio against the total length.
+            for (int k = 0; k < indexDelta; k++) {
+                int skippedUmbraIndex = (previousClosestUmbraIndex + k + 1) % umbraLength;
+                skippedUmbra = umbra[skippedUmbraIndex];
+                float currentDeltaLength = (skippedUmbra - previousClosestUmbra).length();
+
+                totalDeltaLength += currentDeltaLength;
+                accumulatedDeltaLength[k] = totalDeltaLength;
+
+                previousClosestUmbra = skippedUmbra;
             }
-            currentDistance = distances[i];
-            if (currentDistance != 0) {
-                bool currentOuter = allVerticesAngleData[i].mIsPenumbra;
-                for (int j = 1; j <= (currentDistance - 1); j++) {
-                    bool neigborOuter =
-                            allVerticesAngleData[(i + angleLength - j) % angleLength].mIsPenumbra;
-                    if (neigborOuter != currentOuter) {
-                        ALOGE("Wrong distance found at i %d name %s", i, name);
-                    }
-                }
-                bool oppositeOuter =
-                    allVerticesAngleData[(i + angleLength - currentDistance) % angleLength].mIsPenumbra;
-                if (oppositeOuter == currentOuter) {
-                    ALOGE("Wrong distance found at i %d name %s", i, name);
-                }
-            }
-        }
-    }
-}
 
-/**
- * DEBUG ONLY: Verify all the angle data compuated are  is correctly done
- */
-static void verifyAngleData(int totalRayNumber, const VertexAngleData* allVerticesAngleData,
-        const int* distancesToInner, const int* distancesToOuter,
-        const VertexAngleData* umbraAngleList, int maxUmbraAngleIndex, int umbraLength,
-        const VertexAngleData* penumbraAngleList, int maxPenumbraAngleIndex,
-        int penumbraLength) {
-    for (int i = 0; i < totalRayNumber; i++) {
-        ALOGD("currentAngleList i %d, angle %f, isInner %d, index %d distancesToInner"
-              " %d distancesToOuter %d", i, allVerticesAngleData[i].mAngle,
-                !allVerticesAngleData[i].mIsPenumbra,
-                allVerticesAngleData[i].mVertexIndex, distancesToInner[i], distancesToOuter[i]);
-    }
+            const Vector2& previousPenumbra = penumbra[(i + penumbraLength - 1) % penumbraLength];
+            // Then for each unpaired umbra vertex, create a new penumbra by the ratio,
+            // and pair them togehter.
+            for (int k = 0; k < newPenumbraNumber; k++) {
+                float weightForCurrentPenumbra = 1.0f;
+                if (totalDeltaLength != 0.0f) {
+                    weightForCurrentPenumbra = accumulatedDeltaLength[k] / totalDeltaLength;
+                }
+                float weightForPreviousPenumbra = 1.0f - weightForCurrentPenumbra;
 
-    verifyDistanceCounter(allVerticesAngleData, distancesToInner, totalRayNumber, "distancesToInner");
-    verifyDistanceCounter(allVerticesAngleData, distancesToOuter, totalRayNumber, "distancesToOuter");
+                Vector2 interpolatedPenumbra = currentPenumbraVertex * weightForCurrentPenumbra +
+                    previousPenumbra * weightForPreviousPenumbra;
 
-    for (int i = 0; i < totalRayNumber; i++) {
-        if ((distancesToInner[i] * distancesToOuter[i]) != 0) {
-            ALOGE("distancesToInner wrong at index %d distancesToInner[i] %d,"
-                    " distancesToOuter[i] %d", i, distancesToInner[i], distancesToOuter[i]);
-        }
-    }
-    int currentUmbraVertexIndex =
-            umbraAngleList[maxUmbraAngleIndex].mVertexIndex;
-    int currentPenumbraVertexIndex =
-            penumbraAngleList[maxPenumbraAngleIndex].mVertexIndex;
-    for (int i = 0; i < totalRayNumber; i++) {
-        if (allVerticesAngleData[i].mIsPenumbra == true) {
-            if (allVerticesAngleData[i].mVertexIndex != currentPenumbraVertexIndex) {
-                ALOGW("wrong penumbra indexing i %d allVerticesAngleData[i].mVertexIndex %d "
-                        "currentpenumbraVertexIndex %d", i,
-                        allVerticesAngleData[i].mVertexIndex, currentPenumbraVertexIndex);
-            }
-            currentPenumbraVertexIndex = (currentPenumbraVertexIndex + 1) % penumbraLength;
-        } else {
-            if (allVerticesAngleData[i].mVertexIndex != currentUmbraVertexIndex) {
-                ALOGW("wrong umbra indexing i %d allVerticesAngleData[i].mVertexIndex %d "
-                        "currentUmbraVertexIndex %d", i,
-                        allVerticesAngleData[i].mVertexIndex, currentUmbraVertexIndex);
+                int skippedUmbraIndex = (previousClosestUmbraIndex + k + 1) % umbraLength;
+                verticesPair[verticesPairIndex++] = {newPenumbraIndex, skippedUmbraIndex};
+                newPenumbra[newPenumbraIndex++] = interpolatedPenumbra;
             }
-            currentUmbraVertexIndex = (currentUmbraVertexIndex + 1) % umbraLength;
         }
-    }
-    for (int i = 0; i < totalRayNumber - 1; i++) {
-        float currentAngle = allVerticesAngleData[i].mAngle;
-        float nextAngle = allVerticesAngleData[(i + 1) % totalRayNumber].mAngle;
-        if (currentAngle < nextAngle) {
-            ALOGE("Unexpected angle values!, currentAngle nextAngle %f %f", currentAngle, nextAngle);
-        }
-    }
-}
-#endif
+        verticesPair[verticesPairIndex++] = {newPenumbraIndex, currentClosestUmbraIndex};
+        newPenumbra[newPenumbraIndex++] = currentPenumbraVertex;
 
-/**
- * In order to compute the occluded umbra, we need to setup the angle data list
- * for the polygon data. Since we only store one poly vertex per polygon vertex,
- * this array only needs to be a float array which are the angles for each vertex.
- *
- * @param polyAngleList The result list
- *
- * @return int The index for the maximum angle in this array.
- */
-int SpotShadow::setupPolyAngleList(float* polyAngleList, int polyAngleLength,
-        const Vector2* poly2d, const Vector2& centroid) {
-    int maxPolyAngleIndex = -1;
-    float maxPolyAngle = -FLT_MAX;
-    for (int i = 0; i < polyAngleLength; i++) {
-        polyAngleList[i] = angle(poly2d[i], centroid);
-        if (polyAngleList[i] > maxPolyAngle) {
-            maxPolyAngle = polyAngleList[i];
-            maxPolyAngleIndex = i;
-        }
+        previousClosestUmbraIndex = currentClosestUmbraIndex;
     }
-    return maxPolyAngleIndex;
-}
-
-/**
- * For umbra and penumbra, given the offset info and the current ray number,
- * find the right edge index (the (starting vertex) for the ray to shoot at.
- *
- * @return int The index of the starting vertex of the edge.
- */
-inline int SpotShadow::getEdgeStartIndex(const int* offsets, int rayIndex, int totalRayNumber,
-        const VertexAngleData* allVerticesAngleData) {
-    int tempOffset = offsets[rayIndex];
-    int targetRayIndex = (rayIndex - tempOffset + totalRayNumber) % totalRayNumber;
-    return allVerticesAngleData[targetRayIndex].mVertexIndex;
 }
 
-/**
- * For the occluded umbra, given the array of angles, find the index of the
- * starting vertex of the edge, for the ray to shoo at.
- *
- * TODO: Save the last result to shorten the search distance.
- *
- * @return int The index of the starting vertex of the edge.
- */
-inline int SpotShadow::getPolyEdgeStartIndex(int maxPolyAngleIndex, int polyLength,
-        const float* polyAngleList, float rayAngle) {
-    int minPolyAngleIndex  = (maxPolyAngleIndex + polyLength - 1) % polyLength;
-    int resultIndex = -1;
-    if (rayAngle > polyAngleList[maxPolyAngleIndex]
-        || rayAngle <= polyAngleList[minPolyAngleIndex]) {
-        resultIndex = minPolyAngleIndex;
-    } else {
-        for (int i = 0; i < polyLength - 1; i++) {
-            int currentIndex = (maxPolyAngleIndex + i) % polyLength;
-            int nextIndex = (maxPolyAngleIndex + i + 1) % polyLength;
-            if (rayAngle <= polyAngleList[currentIndex]
-                && rayAngle > polyAngleList[nextIndex]) {
-                resultIndex = currentIndex;
-            }
-        }
+// Precompute all the polygon's vector, return true if the reference cross product is positive.
+inline bool genPolyToCentroid(const Vector2* poly2d, int polyLength,
+        const Vector2& centroid, Vector2* polyToCentroid) {
+    for (int j = 0; j < polyLength; j++) {
+        polyToCentroid[j] = poly2d[j] - centroid;
     }
-    if (CC_UNLIKELY(resultIndex == -1)) {
-        // TODO: Add more error handling here.
-        ALOGE("Wrong index found, means no edge can't be found for rayAngle %f", rayAngle);
+    float refCrossProduct = 0;
+    for (int j = 0; j < polyLength; j++) {
+        refCrossProduct = polyToCentroid[j].cross(polyToCentroid[(j + 1) % polyLength]);
+        if (refCrossProduct != 0) {
+            break;
+        }
     }
-    return resultIndex;
+
+    return refCrossProduct > 0;
 }
 
-/**
- * Convert the incoming polygons into arrays of vertices, for each ray.
- * Ray only shoots when there is one vertex either on penumbra on umbra.
- *
- * Finally, it will generate vertices per ray for umbra, penumbra and optionally
- * occludedUmbra.
- *
- * Return true (success) when all vertices are generated
- */
-int SpotShadow::convertPolysToVerticesPerRay(
-        bool hasOccludedUmbraArea, const Vector2* poly2d, int polyLength,
-        const Vector2* umbra, int umbraLength, const Vector2* penumbra,
-        int penumbraLength, const Vector2& centroid,
-        Vector2* umbraVerticesPerRay, Vector2* penumbraVerticesPerRay,
-        Vector2* occludedUmbraVerticesPerRay) {
-    int totalRayNumber = umbraLength + penumbraLength;
-
-    // For incoming umbra / penumbra polygons, we will build an intermediate data
-    // structure to help us sort all the vertices according to the vertices.
-    // Using this data structure, we can tell where (the angle) to shoot the ray,
-    // whether we shoot at penumbra edge or umbra edge, and which edge to shoot at.
-    //
-    // We first parse each vertices and generate a table of VertexAngleData.
-    // Based on that, we create 2 arrays telling us which edge to shoot at.
-    VertexAngleData allVerticesAngleData[totalRayNumber];
-    VertexAngleData umbraAngleList[umbraLength];
-    VertexAngleData penumbraAngleList[penumbraLength];
-
-    int polyAngleLength = hasOccludedUmbraArea ? polyLength : 0;
-    float polyAngleList[polyAngleLength];
-
-    const int maxUmbraAngleIndex =
-            setupAngleList(umbraAngleList, umbraLength, umbra, centroid, false, "umbra");
-    const int maxPenumbraAngleIndex =
-            setupAngleList(penumbraAngleList, penumbraLength, penumbra, centroid, true, "penumbra");
-    const int maxPolyAngleIndex = setupPolyAngleList(polyAngleList, polyAngleLength, poly2d, centroid);
-
-    // Check all the polygons here are CW.
-    bool isPolyCW = checkPolyClockwise(polyAngleLength, maxPolyAngleIndex, polyAngleList);
-    bool isUmbraCW = checkClockwise(maxUmbraAngleIndex, umbraLength,
-            umbraAngleList, "umbra");
-    bool isPenumbraCW = checkClockwise(maxPenumbraAngleIndex, penumbraLength,
-            penumbraAngleList, "penumbra");
-
-    if (!isUmbraCW || !isPenumbraCW || !isPolyCW) {
-#if DEBUG_SHADOW
-        ALOGE("One polygon is not CW isUmbraCW %d isPenumbraCW %d isPolyCW %d",
-                isUmbraCW, isPenumbraCW, isPolyCW);
-#endif
-        return false;
+// For one umbra vertex, shoot an ray from centroid to it.
+// If the ray hit the polygon first, then return the intersection point as the
+// closer vertex.
+inline Vector2 getCloserVertex(const Vector2& umbraVertex, const Vector2& centroid,
+        const Vector2* poly2d, int polyLength, const Vector2* polyToCentroid,
+        bool isPositiveCross, int& previousPolyIndex) {
+    Vector2 umbraToCentroid = umbraVertex - centroid;
+    float distanceToUmbra = umbraToCentroid.length();
+    umbraToCentroid = umbraToCentroid / distanceToUmbra;
+
+    // previousPolyIndex is updated for each item such that we can minimize the
+    // looping inside findPolyIndex();
+    previousPolyIndex = findPolyIndex(isPositiveCross, previousPolyIndex,
+            umbraToCentroid, polyToCentroid, polyLength);
+
+    float dx = umbraToCentroid.x;
+    float dy = umbraToCentroid.y;
+    float distanceToIntersectPoly = rayIntersectPoints(centroid, dx, dy,
+            poly2d[previousPolyIndex], poly2d[(previousPolyIndex + 1) % polyLength]);
+    if (distanceToIntersectPoly < 0) {
+        distanceToIntersectPoly = 0;
     }
 
-    mergeAngleList(maxUmbraAngleIndex, maxPenumbraAngleIndex,
-            umbraAngleList, umbraLength, penumbraAngleList, penumbraLength,
-            allVerticesAngleData);
-
-    // Calculate the offset to the left most Inner vertex for each outerVertex.
-    // Then the offset to the left most Outer vertex for each innerVertex.
-    int offsetToInner[totalRayNumber];
-    int offsetToOuter[totalRayNumber];
-    calculateDistanceCounter(true, totalRayNumber, allVerticesAngleData, offsetToInner);
-    calculateDistanceCounter(false, totalRayNumber, allVerticesAngleData, offsetToOuter);
-
-    // Generate both umbraVerticesPerRay and penumbraVerticesPerRay
-    for (int i = 0; i < totalRayNumber; i++) {
-        float rayAngle = allVerticesAngleData[i].mAngle;
-        bool isUmbraVertex = !allVerticesAngleData[i].mIsPenumbra;
-
-        float dx = cosf(rayAngle);
-        float dy = sinf(rayAngle);
-        float distanceToIntersectUmbra = -1;
-
-        if (isUmbraVertex) {
-            // We can just copy umbra easily, and calculate the distance for the
-            // occluded umbra computation.
-            int startUmbraIndex = allVerticesAngleData[i].mVertexIndex;
-            umbraVerticesPerRay[i] = umbra[startUmbraIndex];
-            if (hasOccludedUmbraArea) {
-                distanceToIntersectUmbra = (umbraVerticesPerRay[i] - centroid).length();
-            }
-
-            //shoot ray to penumbra only
-            int startPenumbraIndex = getEdgeStartIndex(offsetToOuter, i, totalRayNumber,
-                    allVerticesAngleData);
-            float distanceToIntersectPenumbra = rayIntersectPoints(centroid, dx, dy,
-                    penumbra[startPenumbraIndex],
-                    penumbra[(startPenumbraIndex + 1) % penumbraLength]);
-            if (distanceToIntersectPenumbra < 0) {
-#if DEBUG_SHADOW
-                ALOGW("convertPolyToRayDist for penumbra failed rayAngle %f dx %f dy %f",
-                        rayAngle, dx, dy);
-#endif
-                distanceToIntersectPenumbra = 0;
-            }
-            penumbraVerticesPerRay[i].x = centroid.x + dx * distanceToIntersectPenumbra;
-            penumbraVerticesPerRay[i].y = centroid.y + dy * distanceToIntersectPenumbra;
-        } else {
-            // We can just copy the penumbra
-            int startPenumbraIndex = allVerticesAngleData[i].mVertexIndex;
-            penumbraVerticesPerRay[i] = penumbra[startPenumbraIndex];
-
-            // And shoot ray to umbra only
-            int startUmbraIndex = getEdgeStartIndex(offsetToInner, i, totalRayNumber,
-                    allVerticesAngleData);
-
-            distanceToIntersectUmbra = rayIntersectPoints(centroid, dx, dy,
-                    umbra[startUmbraIndex], umbra[(startUmbraIndex + 1) % umbraLength]);
-            if (distanceToIntersectUmbra < 0) {
-#if DEBUG_SHADOW
-                ALOGW("convertPolyToRayDist for umbra failed rayAngle %f dx %f dy %f",
-                        rayAngle, dx, dy);
-#endif
-                distanceToIntersectUmbra = 0;
-            }
-            umbraVerticesPerRay[i].x = centroid.x + dx * distanceToIntersectUmbra;
-            umbraVerticesPerRay[i].y = centroid.y + dy * distanceToIntersectUmbra;
-        }
-
-        if (hasOccludedUmbraArea) {
-            // Shoot the same ray to the poly2d, and get the distance.
-            int startPolyIndex = getPolyEdgeStartIndex(maxPolyAngleIndex, polyLength,
-                    polyAngleList, rayAngle);
-
-            float distanceToIntersectPoly = rayIntersectPoints(centroid, dx, dy,
-                    poly2d[startPolyIndex], poly2d[(startPolyIndex + 1) % polyLength]);
-            if (distanceToIntersectPoly < 0) {
-                distanceToIntersectPoly = 0;
-            }
-            distanceToIntersectPoly = MathUtils::min(distanceToIntersectUmbra, distanceToIntersectPoly);
-            occludedUmbraVerticesPerRay[i].x = centroid.x + dx * distanceToIntersectPoly;
-            occludedUmbraVerticesPerRay[i].y = centroid.y + dy * distanceToIntersectPoly;
-        }
+    // Pick the closer one as the occluded area vertex.
+    Vector2 closerVertex;
+    if (distanceToIntersectPoly < distanceToUmbra) {
+        closerVertex.x = centroid.x + dx * distanceToIntersectPoly;
+        closerVertex.y = centroid.y + dy * distanceToIntersectPoly;
+    } else {
+        closerVertex = umbraVertex;
     }
 
-#if DEBUG_SHADOW
-    verifyAngleData(totalRayNumber, allVerticesAngleData, offsetToInner,
-            offsetToOuter,  umbraAngleList, maxUmbraAngleIndex,  umbraLength,
-            penumbraAngleList,  maxPenumbraAngleIndex, penumbraLength);
-#endif
-    return true; // success
-
+    return closerVertex;
 }
 
 /**
@@ -1193,7 +864,6 @@ void SpotShadow::generateTriangleStrip(bool isCasterOpaque, float shadowStrength
         Vector2* penumbra, int penumbraLength, Vector2* umbra, int umbraLength,
         const Vector3* poly, int polyLength, VertexBuffer& shadowTriangleStrip,
         const Vector2& centroid) {
-
     bool hasOccludedUmbraArea = false;
     Vector2 poly2d[polyLength];
 
@@ -1209,128 +879,140 @@ void SpotShadow::generateTriangleStrip(bool isCasterOpaque, float shadowStrength
         }
     }
 
-    int totalRayNum = umbraLength + penumbraLength;
-    Vector2 umbraVertices[totalRayNum];
-    Vector2 penumbraVertices[totalRayNum];
-    Vector2 occludedUmbraVertices[totalRayNum];
-    bool convertSuccess = convertPolysToVerticesPerRay(hasOccludedUmbraArea, poly2d,
-            polyLength, umbra, umbraLength, penumbra, penumbraLength,
-            centroid, umbraVertices, penumbraVertices, occludedUmbraVertices);
-    if (!convertSuccess) {
-        return;
+    // For each penumbra vertex, find its corresponding closest umbra vertex index.
+    //
+    // Penumbra Vertices marked as Pi
+    // Umbra Vertices marked as Ui
+    //                                            (P3)
+    //          (P2)                               |     ' (P4)
+    //   (P1)'   |                                 |   '
+    //         ' |                                 | '
+    // (P0)  ------------------------------------------------(P5)
+    //           | (U0)                            |(U1)
+    //           |                                 |
+    //           |                                 |(U2)     (P5.1)
+    //           |                                 |
+    //           |                                 |
+    //           |                                 |
+    //           |                                 |
+    //           |                                 |
+    //           |                                 |
+    //       (U4)-----------------------------------(U3)      (P6)
+    //
+    // At least, like P0, P1, P2, they will find the matching umbra as U0.
+    // If we jump over some umbra vertex without matching penumbra vertex, then
+    // we will generate some new penumbra vertex by interpolation. Like P6 is
+    // matching U3, but U2 is not matched with any penumbra vertex.
+    // So interpolate P5.1 out and match U2.
+    // In this way, every umbra vertex will have a matching penumbra vertex.
+    //
+    // The total pair number can be as high as umbraLength + penumbraLength.
+    const int maxNewPenumbraLength = umbraLength + penumbraLength;
+    IndexPair verticesPair[maxNewPenumbraLength];
+    int verticesPairIndex = 0;
+
+    // Cache all the existing penumbra vertices and newly interpolated vertices into a
+    // a new array.
+    Vector2 newPenumbra[maxNewPenumbraLength];
+    int newPenumbraIndex = 0;
+
+    // For each penumbra vertex, find its closet umbra vertex by comparing the
+    // neighbor umbra vertices.
+    genNewPenumbraAndPairWithUmbra(penumbra, penumbraLength, umbra, umbraLength, newPenumbra,
+            newPenumbraIndex, verticesPair, verticesPairIndex);
+    ShadowTessellator::checkOverflow(verticesPairIndex, maxNewPenumbraLength, "Spot pair");
+    ShadowTessellator::checkOverflow(newPenumbraIndex, maxNewPenumbraLength, "Spot new penumbra");
+#if DEBUG_SHADOW
+    for (int i = 0; i < umbraLength; i++) {
+        ALOGD("umbra i %d,  [%f, %f]", i, umbra[i].x, umbra[i].y);
+    }
+    for (int i = 0; i < newPenumbraIndex; i++) {
+        ALOGD("new penumbra i %d,  [%f, %f]", i, newPenumbra[i].x, newPenumbra[i].y);
+    }
+    for (int i = 0; i < verticesPairIndex; i++) {
+        ALOGD("index i %d,  [%d, %d]", i, verticesPair[i].outerIndex, verticesPair[i].innerIndex);
     }
+#endif
 
-    // Minimal value is 1, for each vertex show up once.
-    // The bigger this value is , the smoother the look is, but more memory
-    // is consumed.
-    // When the ray number is high, that means the polygon has been fine
-    // tessellated, we don't need this extra slice, just keep it as 1.
-    int sliceNumberPerEdge = (totalRayNum > FINE_TESSELLATED_POLYGON_RAY_NUMBER) ? 1 : 2;
-
-    // For each polygon, we at most add (totalRayNum * sliceNumberPerEdge) vertices.
-    int slicedVertexCountPerPolygon = totalRayNum * sliceNumberPerEdge;
-    int totalVertexCount = slicedVertexCountPerPolygon * 2 + totalRayNum;
-    int totalIndexCount = 2 * (slicedVertexCountPerPolygon * 2 + 2);
+    // For the size of vertex buffer, we need 3 rings, one has newPenumbraSize,
+    // one has umbraLength, the last one has at most umbraLength.
+    //
+    // For the size of index buffer, the umbra area needs (2 * umbraLength + 2).
+    // The penumbra one can vary a bit, but it is bounded by (2 * verticesPairIndex + 2).
+    // And 2 more for jumping between penumbra to umbra.
+    const int newPenumbraLength = newPenumbraIndex;
+    const int totalVertexCount = newPenumbraLength + umbraLength * 2;
+    const int totalIndexCount = 2 * umbraLength + 2 * verticesPairIndex + 6;
     AlphaVertex* shadowVertices =
             shadowTriangleStrip.alloc<AlphaVertex>(totalVertexCount);
     uint16_t* indexBuffer =
             shadowTriangleStrip.allocIndices<uint16_t>(totalIndexCount);
-
-    int indexBufferIndex = 0;
     int vertexBufferIndex = 0;
+    int indexBufferIndex = 0;
 
-    uint16_t slicedUmbraVertexIndex[totalRayNum * sliceNumberPerEdge];
-    // Should be something like 0 0 0  1 1 1 2 3 3 3...
-    int rayNumberPerSlicedUmbra[totalRayNum * sliceNumberPerEdge];
-    int realUmbraVertexCount = 0;
-    for (int i = 0; i < totalRayNum; i++) {
-        Vector2 currentPenumbra = penumbraVertices[i];
-        Vector2 currentUmbra = umbraVertices[i];
-
-        Vector2 nextPenumbra = penumbraVertices[(i + 1) % totalRayNum];
-        Vector2 nextUmbra = umbraVertices[(i + 1) % totalRayNum];
-        // NextUmbra/Penumbra will be done in the next loop!!
-        for (int weight = 0; weight < sliceNumberPerEdge; weight++) {
-            const Vector2& slicedPenumbra = (currentPenumbra * (sliceNumberPerEdge - weight)
-                + nextPenumbra * weight) / sliceNumberPerEdge;
-
-            const Vector2& slicedUmbra = (currentUmbra * (sliceNumberPerEdge - weight)
-                + nextUmbra * weight) / sliceNumberPerEdge;
-
-            // In the vertex buffer, we fill the Penumbra first, then umbra.
-            indexBuffer[indexBufferIndex++] = vertexBufferIndex;
-            AlphaVertex::set(&shadowVertices[vertexBufferIndex++], slicedPenumbra.x,
-                    slicedPenumbra.y, 0.0f);
-
-            // When we add umbra vertex, we need to remember its current ray number.
-            // And its own vertexBufferIndex. This is for occluded umbra usage.
-            indexBuffer[indexBufferIndex++] = vertexBufferIndex;
-            rayNumberPerSlicedUmbra[realUmbraVertexCount] = i;
-            slicedUmbraVertexIndex[realUmbraVertexCount] = vertexBufferIndex;
-            realUmbraVertexCount++;
-            AlphaVertex::set(&shadowVertices[vertexBufferIndex++], slicedUmbra.x,
-                    slicedUmbra.y, M_PI);
-        }
+    // Fill the IB and VB for the penumbra area.
+    for (int i = 0; i < newPenumbraLength; i++) {
+        AlphaVertex::set(&shadowVertices[vertexBufferIndex++], newPenumbra[i].x,
+                newPenumbra[i].y, 0.0f);
+    }
+    for (int i = 0; i < umbraLength; i++) {
+        AlphaVertex::set(&shadowVertices[vertexBufferIndex++], umbra[i].x, umbra[i].y,
+                M_PI);
     }
 
-    indexBuffer[indexBufferIndex++] = 0;
-    //RealUmbraVertexIndex[0] must be 1, so we connect back well at the
-    //beginning of occluded area.
-    indexBuffer[indexBufferIndex++] = 1;
+    for (int i = 0; i < verticesPairIndex; i++) {
+        indexBuffer[indexBufferIndex++] = verticesPair[i].outerIndex;
+        // All umbra index need to be offseted by newPenumbraSize.
+        indexBuffer[indexBufferIndex++] = verticesPair[i].innerIndex + newPenumbraLength;
+    }
+    indexBuffer[indexBufferIndex++] = verticesPair[0].outerIndex;
+    indexBuffer[indexBufferIndex++] = verticesPair[0].innerIndex + newPenumbraLength;
+
+    // Now fill the IB and VB for the umbra area.
+    // First duplicated the index from previous strip and the first one for the
+    // degenerated triangles.
+    indexBuffer[indexBufferIndex] = indexBuffer[indexBufferIndex - 1];
+    indexBufferIndex++;
+    indexBuffer[indexBufferIndex++] = newPenumbraLength + 0;
+    // Save the first VB index for umbra area in order to close the loop.
+    int savedStartIndex = vertexBufferIndex;
 
-    float occludedUmbraAlpha = M_PI;
     if (hasOccludedUmbraArea) {
-        // Now the occludedUmbra area;
-        int currentRayNumber = -1;
-        int firstOccludedUmbraIndex = -1;
-        for (int i = 0; i < realUmbraVertexCount; i++) {
-            indexBuffer[indexBufferIndex++] = slicedUmbraVertexIndex[i];
-
-            // If the occludedUmbra vertex has not been added yet, then add it.
-            // Otherwise, just use the previously added occludedUmbra vertices.
-            if (rayNumberPerSlicedUmbra[i] != currentRayNumber) {
-                currentRayNumber++;
-                indexBuffer[indexBufferIndex++] = vertexBufferIndex;
-                // We need to remember the begining of the occludedUmbra vertices
-                // to close this loop.
-                if (currentRayNumber == 0) {
-                    firstOccludedUmbraIndex = vertexBufferIndex;
-                }
-                AlphaVertex::set(&shadowVertices[vertexBufferIndex++],
-                        occludedUmbraVertices[currentRayNumber].x,
-                        occludedUmbraVertices[currentRayNumber].y,
-                        occludedUmbraAlpha);
-            } else {
-                indexBuffer[indexBufferIndex++] = (vertexBufferIndex - 1);
-            }
+        // Precompute all the polygon's vector, and the reference cross product,
+        // in order to find the right polygon edge for the ray to intersect.
+        Vector2 polyToCentroid[polyLength];
+        bool isPositiveCross = genPolyToCentroid(poly2d, polyLength, centroid, polyToCentroid);
+
+        // Because both the umbra and polygon are going in the same direction,
+        // we can save the previous polygon index to make sure we have less polygon
+        // vertex to compute for each ray.
+        int previousPolyIndex = 0;
+        for (int i = 0; i < umbraLength; i++) {
+            // Shoot a ray from centroid to each umbra vertices and pick the one with
+            // shorter distance to the centroid, b/t the umbra vertex or the intersection point.
+            Vector2 closerVertex = getCloserVertex(umbra[i], centroid, poly2d, polyLength,
+                    polyToCentroid, isPositiveCross, previousPolyIndex);
+
+            // We already stored the umbra vertices, just need to add the occlued umbra's ones.
+            indexBuffer[indexBufferIndex++] = newPenumbraLength + i;
+            indexBuffer[indexBufferIndex++] = vertexBufferIndex;
+            AlphaVertex::set(&shadowVertices[vertexBufferIndex++],
+                    closerVertex.x, closerVertex.y, M_PI);
         }
-        // Close the loop here!
-        indexBuffer[indexBufferIndex++] = slicedUmbraVertexIndex[0];
-        indexBuffer[indexBufferIndex++] = firstOccludedUmbraIndex;
     } else {
+        // If there is no occluded umbra at all, then draw the triangle fan
+        // starting from the centroid to all umbra vertices.
         int lastCentroidIndex = vertexBufferIndex;
         AlphaVertex::set(&shadowVertices[vertexBufferIndex++], centroid.x,
-                centroid.y, occludedUmbraAlpha);
-        for (int i = 0; i < realUmbraVertexCount; i++) {
-            indexBuffer[indexBufferIndex++] = slicedUmbraVertexIndex[i];
+                centroid.y, M_PI);
+        for (int i = 0; i < umbraLength; i++) {
+            indexBuffer[indexBufferIndex++] = newPenumbraLength + i;
             indexBuffer[indexBufferIndex++] = lastCentroidIndex;
         }
-        // Close the loop here!
-        indexBuffer[indexBufferIndex++] = slicedUmbraVertexIndex[0];
-        indexBuffer[indexBufferIndex++] = lastCentroidIndex;
     }
-
-#if DEBUG_SHADOW
-    ALOGD("allocated IB %d allocated VB is %d", totalIndexCount, totalVertexCount);
-    ALOGD("IB index %d VB index is %d", indexBufferIndex, vertexBufferIndex);
-    for (int i = 0; i < vertexBufferIndex; i++) {
-        ALOGD("vertexBuffer i %d, (%f, %f %f)", i, shadowVertices[i].x, shadowVertices[i].y,
-                shadowVertices[i].alpha);
-    }
-    for (int i = 0; i < indexBufferIndex; i++) {
-        ALOGD("indexBuffer i %d, indexBuffer[i] %d", i, indexBuffer[i]);
-    }
-#endif
+    // Closing the umbra area triangle's loop here.
+    indexBuffer[indexBufferIndex++] = newPenumbraLength;
+    indexBuffer[indexBufferIndex++] = savedStartIndex;
 
     // At the end, update the real index and vertex buffer size.
     shadowTriangleStrip.updateVertexCount(vertexBufferIndex);