Add utility method Matrix.perspectiveM

Change-Id: Ic9d5e5d967bbc08acc524c5092ce61a1cdbfd360

1 files changed, 37 insertions, 2 deletions

diff --git a/opengl/java/android/opengl/Matrix.java b/opengl/java/android/opengl/Matrix.java
index b9fd4ab..a412a43 100644
--- a/opengl/java/android/opengl/Matrix.java
+++ b/opengl/java/android/opengl/Matrix.java
@@ -16,8 +16,6 @@
 
 package android.opengl;
 
-import javax.microedition.khronos.opengles.GL10;
-
 /**
  * Matrix math utilities. These methods operate on OpenGL ES format
  * matrices and vectors stored in float arrays.
@@ -332,6 +330,43 @@ public class Matrix {
     }
 
     /**
+     * Define a projection matrix in terms of a field of view angle, an
+     * aspect ratio, and z clip planes
+     * @param m the float array that holds the perspective matrix
+     * @param offset the offset into float array m where the perspective
+     * matrix data is written
+     * @param fovy field of view in y direction, in degrees
+     * @param aspect width to height aspect ratio of the viewport
+     * @param zNear
+     * @param zFar
+     */
+    public static void perspectiveM(float[] m, int offset,
+          float fovy, float aspect, float zNear, float zFar) {
+        float f = 1.0f / (float) Math.tan(fovy * (Math.PI / 360.0));
+        float rangeReciprocal = 1.0f / (zNear - zFar);
+
+        m[offset + 0] = f / aspect;
+        m[offset + 1] = 0.0f;
+        m[offset + 2] = 0.0f;
+        m[offset + 3] = 0.0f;
+
+        m[offset + 4] = 0.0f;
+        m[offset + 5] = f;
+        m[offset + 6] = 0.0f;
+        m[offset + 7] = 0.0f;
+
+        m[offset + 8] = 0.0f;
+        m[offset + 9] = 0.0f;
+        m[offset + 10] = (zFar + zNear) * rangeReciprocal;
+        m[offset + 11] = -1.0f;
+
+        m[offset + 12] = 0.0f;
+        m[offset + 13] = 0.0f;
+        m[offset + 14] = 2.0f * zFar * rangeReciprocal;
+        m[offset + 15] = 0.0f;
+    }
+
+    /**
      * Computes the length of a vector
      *
      * @param x x coordinate of a vector