Texturing and Shading - Learn OpenGL ES: For Mobile Game and Graphics Development - page 212

shading effects, I have made it optional to rotate the light source
( Listing 5-15 ) . The vertex shader code in Listing 5-16 consists of
a uniform variable uMVLight to store the MV matrix
_pointMVMatrix for the light source.
Listing 5-15. VERTEX POINT LIGHTING/src/com/apress/android/vertexpoint-
lighting/GLES20Renderer.java
if(!_rotatePointOnly) {
Matrix.setIdentityM(_tankRMatrix, 0);
Matrix.rotateM(_tankRMatrix, 0, _zAngle, 0, 0, 1);
}
Matrix.multiplyMM(_tankMVPMatrix, 0, _ViewMatrix, 0,
_tankRMatrix, 0);
if(_rotatePointOnly) {
Matrix.rotateM(_pointRMatrix, 0, _zAngle * 0.5f, 0,
0, 1);
Matrix.multiplyMM(_pointMVMatrix, 0, _ViewMatrix, 0,
_pointRMatrix, 0);
Matrix.multiplyMM(_pointMVPMatrix, 0,
_ProjectionMatrix, 0, _pointMVMatrix, 0);
}
▪ The uniform variable uMV inside the vertex shader stores the MV
matrix for the object. This matrix is obtained by copying the en-
tire MVP matrix before the MVP matrix is combined with projec-
tion transformation. As shown in Listing 5-14 , the Sys-
tem.arraycopy method is used to copy the MVP matrix to
MV matrix for the object. You need this MV matrix to transform
the vertex positions into eye-space.
Listing 5-16. VERTEX POINT LIGHTING/src/com/apress/android/vertexpoint-
lighting/GLES20Renderer.java
private final String _tankVertexShaderCode =
"attribute vec3 aPosition; \n"
+ "attribute vec3 aNormal; \n"
+ "varying float diffuseIntensity; \n"
+ "uniform mat3 uNormal; \n"