summaryrefslogtreecommitdiffstats
path: root/libs/hwui/AmbientShadow.cpp
diff options
context:
space:
mode:
Diffstat (limited to 'libs/hwui/AmbientShadow.cpp')
-rw-r--r--libs/hwui/AmbientShadow.cpp326
1 files changed, 326 insertions, 0 deletions
diff --git a/libs/hwui/AmbientShadow.cpp b/libs/hwui/AmbientShadow.cpp
new file mode 100644
index 0000000..c1af5f5
--- /dev/null
+++ b/libs/hwui/AmbientShadow.cpp
@@ -0,0 +1,326 @@
+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#define LOG_TAG "OpenGLRenderer"
+
+#include <math.h>
+#include <utils/Log.h>
+#include <utils/Vector.h>
+
+#include "AmbientShadow.h"
+#include "ShadowTessellator.h"
+#include "Vertex.h"
+
+namespace android {
+namespace uirenderer {
+
+/**
+ * Calculate the shadows as a triangle strips while alpha value as the
+ * shadow values.
+ *
+ * @param isCasterOpaque Whether the caster is opaque.
+ * @param vertices The shadow caster's polygon, which is represented in a Vector3
+ * array.
+ * @param vertexCount The length of caster's polygon in terms of number of
+ * vertices.
+ * @param centroid3d The centroid of the shadow caster.
+ * @param heightFactor The factor showing the higher the object, the lighter the
+ * shadow.
+ * @param geomFactor The factor scaling the geometry expansion along the normal.
+ *
+ * @param shadowVertexBuffer Return an floating point array of (x, y, a)
+ * triangle strips mode.
+ */
+VertexBufferMode AmbientShadow::createAmbientShadow(bool isCasterOpaque,
+ const Vector3* vertices, int vertexCount, const Vector3& centroid3d,
+ float heightFactor, float geomFactor, VertexBuffer& shadowVertexBuffer) {
+ const int rays = SHADOW_RAY_COUNT;
+ VertexBufferMode mode = kVertexBufferMode_OnePolyRingShadow;
+ // Validate the inputs.
+ if (vertexCount < 3 || heightFactor <= 0 || rays <= 0
+ || geomFactor <= 0) {
+#if DEBUG_SHADOW
+ ALOGW("Invalid input for createAmbientShadow(), early return!");
+#endif
+ return mode; // vertex buffer is empty, so any mode doesn't matter.
+ }
+
+ Vector<Vector2> dir; // TODO: use C++11 unique_ptr
+ dir.setCapacity(rays);
+ float rayDist[rays];
+ float rayHeight[rays];
+ calculateRayDirections(rays, vertices, vertexCount, centroid3d, dir.editArray());
+
+ // Calculate the length and height of the points along the edge.
+ //
+ // The math here is:
+ // Intersect each ray (starting from the centroid) with the polygon.
+ for (int i = 0; i < rays; i++) {
+ int edgeIndex;
+ float edgeFraction;
+ float rayDistance;
+ calculateIntersection(vertices, vertexCount, centroid3d, dir[i], edgeIndex,
+ edgeFraction, rayDistance);
+ rayDist[i] = rayDistance;
+ if (edgeIndex < 0 || edgeIndex >= vertexCount) {
+#if DEBUG_SHADOW
+ ALOGW("Invalid edgeIndex!");
+#endif
+ edgeIndex = 0;
+ }
+ float h1 = vertices[edgeIndex].z;
+ float h2 = vertices[((edgeIndex + 1) % vertexCount)].z;
+ rayHeight[i] = h1 + edgeFraction * (h2 - h1);
+ }
+
+ // The output buffer length basically is roughly rays * layers, but since we
+ // need triangle strips, so we need to duplicate vertices to accomplish that.
+ AlphaVertex* shadowVertices =
+ shadowVertexBuffer.alloc<AlphaVertex>(SHADOW_VERTEX_COUNT);
+
+ // Calculate the vertex of the shadows.
+ //
+ // The math here is:
+ // Along the edges of the polygon, for each intersection point P (generated above),
+ // calculate the normal N, which should be perpendicular to the edge of the
+ // polygon (represented by the neighbor intersection points) .
+ // Shadow's vertices will be generated as : P + N * scale.
+ const Vector2 centroid2d = Vector2(centroid3d.x, centroid3d.y);
+ for (int rayIndex = 0; rayIndex < rays; rayIndex++) {
+ Vector2 normal(1.0f, 0.0f);
+ calculateNormal(rays, rayIndex, dir.array(), rayDist, normal);
+
+ // The vertex should be start from rayDist[i] then scale the
+ // normalizeNormal!
+ Vector2 intersection = dir[rayIndex] * rayDist[rayIndex] +
+ centroid2d;
+
+ // outer ring of points, expanded based upon height of each ray intersection
+ float expansionDist = rayHeight[rayIndex] * heightFactor *
+ geomFactor;
+ AlphaVertex::set(&shadowVertices[rayIndex],
+ intersection.x + normal.x * expansionDist,
+ intersection.y + normal.y * expansionDist,
+ 0.0f);
+
+ // inner ring of points
+ float opacity = 1.0 / (1 + rayHeight[rayIndex] * heightFactor);
+ AlphaVertex::set(&shadowVertices[rays + rayIndex],
+ intersection.x,
+ intersection.y,
+ opacity);
+ }
+
+ // If caster isn't opaque, we need to to fill the umbra by storing the umbra's
+ // centroid in the innermost ring of vertices.
+ if (!isCasterOpaque) {
+ mode = kVertexBufferMode_TwoPolyRingShadow;
+ float centroidAlpha = 1.0 / (1 + centroid3d.z * heightFactor);
+ AlphaVertex centroidXYA;
+ AlphaVertex::set(&centroidXYA, centroid2d.x, centroid2d.y, centroidAlpha);
+ for (int rayIndex = 0; rayIndex < rays; rayIndex++) {
+ shadowVertices[2 * rays + rayIndex] = centroidXYA;
+ }
+ }
+
+#if DEBUG_SHADOW
+ for (int i = 0; i < SHADOW_VERTEX_COUNT; i++) {
+ ALOGD("ambient shadow value: i %d, (x:%f, y:%f, a:%f)", i, shadowVertices[i].x,
+ shadowVertices[i].y, shadowVertices[i].alpha);
+ }
+#endif
+ return mode;
+}
+
+/**
+ * Generate an array of rays' direction vectors.
+ * To make sure the vertices generated are clockwise, the directions are from PI
+ * to -PI.
+ *
+ * @param rays The number of rays shooting out from the centroid.
+ * @param vertices Vertices of the polygon.
+ * @param vertexCount The number of vertices.
+ * @param centroid3d The centroid of the polygon.
+ * @param dir Return the array of ray vectors.
+ */
+void AmbientShadow::calculateRayDirections(const int rays, const Vector3* vertices,
+ const int vertexCount, const Vector3& centroid3d, Vector2* dir) {
+ // If we don't have enough rays, then fall back to the uniform distribution.
+ if (vertexCount * 2 > rays) {
+ float deltaAngle = 2 * M_PI / rays;
+ for (int i = 0; i < rays; i++) {
+ dir[i].x = cosf(M_PI - deltaAngle * i);
+ dir[i].y = sinf(M_PI - deltaAngle * i);
+ }
+ return;
+ }
+
+ // If we have enough rays, then we assign each vertices a ray, and distribute
+ // the rest uniformly.
+ float rayThetas[rays];
+
+ const int uniformRayCount = rays - vertexCount;
+ const float deltaAngle = 2 * M_PI / uniformRayCount;
+
+ // We have to generate all the vertices' theta anyway and we also need to
+ // find the minimal, so let's precompute it first.
+ // Since the incoming polygon is clockwise, we can find the dip to identify
+ // the minimal theta.
+ float polyThetas[vertexCount];
+ int maxPolyThetaIndex = 0;
+ for (int i = 0; i < vertexCount; i++) {
+ polyThetas[i] = atan2(vertices[i].y - centroid3d.y,
+ vertices[i].x - centroid3d.x);
+ if (i > 0 && polyThetas[i] > polyThetas[i - 1]) {
+ maxPolyThetaIndex = i;
+ }
+ }
+
+ // Both poly's thetas and uniform thetas are in decrease order(clockwise)
+ // from PI to -PI.
+ int polyThetaIndex = maxPolyThetaIndex;
+ float polyTheta = polyThetas[maxPolyThetaIndex];
+ int uniformThetaIndex = 0;
+ float uniformTheta = M_PI;
+ for (int i = 0; i < rays; i++) {
+ // Compare both thetas and pick the smaller one and move on.
+ bool hasThetaCollision = abs(polyTheta - uniformTheta) < MINIMAL_DELTA_THETA;
+ if (polyTheta > uniformTheta || hasThetaCollision) {
+ if (hasThetaCollision) {
+ // Shift the uniformTheta to middle way between current polyTheta
+ // and next uniform theta. The next uniform theta can wrap around
+ // to exactly PI safely here.
+ // Note that neither polyTheta nor uniformTheta can be FLT_MAX
+ // due to the hasThetaCollision is true.
+ uniformTheta = (polyTheta + M_PI - deltaAngle * (uniformThetaIndex + 1)) / 2;
+#if DEBUG_SHADOW
+ ALOGD("Shifted uniformTheta to %f", uniformTheta);
+#endif
+ }
+ rayThetas[i] = polyTheta;
+ polyThetaIndex = (polyThetaIndex + 1) % vertexCount;
+ if (polyThetaIndex != maxPolyThetaIndex) {
+ polyTheta = polyThetas[polyThetaIndex];
+ } else {
+ // out of poly points.
+ polyTheta = - FLT_MAX;
+ }
+ } else {
+ rayThetas[i] = uniformTheta;
+ uniformThetaIndex++;
+ if (uniformThetaIndex < uniformRayCount) {
+ uniformTheta = M_PI - deltaAngle * uniformThetaIndex;
+ } else {
+ // out of uniform points.
+ uniformTheta = - FLT_MAX;
+ }
+ }
+ }
+
+ for (int i = 0; i < rays; i++) {
+#if DEBUG_SHADOW
+ ALOGD("No. %d : %f", i, rayThetas[i] * 180 / M_PI);
+#endif
+ // TODO: Fix the intersection precision problem and remvoe the delta added
+ // here.
+ dir[i].x = cosf(rayThetas[i] + MINIMAL_DELTA_THETA);
+ dir[i].y = sinf(rayThetas[i] + MINIMAL_DELTA_THETA);
+ }
+}
+
+/**
+ * Calculate the intersection of a ray hitting the polygon.
+ *
+ * @param vertices The shadow caster's polygon, which is represented in a
+ * Vector3 array.
+ * @param vertexCount The length of caster's polygon in terms of number of vertices.
+ * @param start The starting point of the ray.
+ * @param dir The direction vector of the ray.
+ *
+ * @param outEdgeIndex Return the index of the segment (or index of the starting
+ * vertex) that ray intersect with.
+ * @param outEdgeFraction Return the fraction offset from the segment starting
+ * index.
+ * @param outRayDist Return the ray distance from centroid to the intersection.
+ */
+void AmbientShadow::calculateIntersection(const Vector3* vertices, int vertexCount,
+ const Vector3& start, const Vector2& dir, int& outEdgeIndex,
+ float& outEdgeFraction, float& outRayDist) {
+ float startX = start.x;
+ float startY = start.y;
+ float dirX = dir.x;
+ float dirY = dir.y;
+ // Start the search from the last edge from poly[len-1] to poly[0].
+ int p1 = vertexCount - 1;
+
+ for (int p2 = 0; p2 < vertexCount; p2++) {
+ float p1x = vertices[p1].x;
+ float p1y = vertices[p1].y;
+ float p2x = vertices[p2].x;
+ float p2y = vertices[p2].y;
+
+ // The math here is derived from:
+ // f(t, v) = p1x * (1 - t) + p2x * t - (startX + dirX * v) = 0;
+ // g(t, v) = p1y * (1 - t) + p2y * t - (startY + dirY * v) = 0;
+ float div = (dirX * (p1y - p2y) + dirY * p2x - dirY * p1x);
+ if (div != 0) {
+ float t = (dirX * (p1y - startY) + dirY * startX - dirY * p1x) / (div);
+ if (t > 0 && t <= 1) {
+ float t2 = (p1x * (startY - p2y)
+ + p2x * (p1y - startY)
+ + startX * (p2y - p1y)) / div;
+ if (t2 > 0) {
+ outEdgeIndex = p1;
+ outRayDist = t2;
+ outEdgeFraction = t;
+ return;
+ }
+ }
+ }
+ p1 = p2;
+ }
+ return;
+};
+
+/**
+ * Calculate the normal at the intersection point between a ray and the polygon.
+ *
+ * @param rays The total number of rays.
+ * @param currentRayIndex The index of the ray which the normal is based on.
+ * @param dir The array of the all the rays directions.
+ * @param rayDist The pre-computed ray distances array.
+ *
+ * @param normal Return the normal.
+ */
+void AmbientShadow::calculateNormal(int rays, int currentRayIndex,
+ const Vector2* dir, const float* rayDist, Vector2& normal) {
+ int preIndex = (currentRayIndex - 1 + rays) % rays;
+ int postIndex = (currentRayIndex + 1) % rays;
+ Vector2 p1 = dir[preIndex] * rayDist[preIndex];
+ Vector2 p2 = dir[postIndex] * rayDist[postIndex];
+
+ // Now the rays are going CW around the poly.
+ Vector2 delta = p2 - p1;
+ if (delta.length() != 0) {
+ delta.normalize();
+ // Calculate the normal , which is CCW 90 rotate to the delta.
+ normal.x = - delta.y;
+ normal.y = delta.x;
+ }
+}
+
+}; // namespace uirenderer
+}; // namespace android
generated by cgit v1.1 at 2025-01-23 12:16:27 +0000