/**
* Allocates and initializes OpenGL resources needed by the background renderer. Must be
* called on the OpenGL thread, typically in
* {@link GLSurfaceView.Renderer#onSurfaceCreated(GL10, EGLConfig)}.
*
* @param context Needed to access shader source.
*/
public void CreateOnGlThread(Context context)
{
// Generate the background texture.
var textures = new int[1];
//GLES20 = OpenGL ES 2.0
//Gibt eine bestimmte Anzahl an freien Texturnamen zurück.
GLES20.GlGenTextures(1, textures, 0);
TextureId = textures[0];
GLES20.GlBindTexture(mTextureTarget, TextureId);
GLES20.GlTexParameteri(mTextureTarget, GLES20.GlTextureWrapS, GLES20.GlClampToEdge);
GLES20.GlTexParameteri(mTextureTarget, GLES20.GlTextureWrapT, GLES20.GlClampToEdge);
GLES20.GlTexParameteri(mTextureTarget, GLES20.GlTextureMinFilter, GLES20.GlNearest);
GLES20.GlTexParameteri(mTextureTarget, GLES20.GlTextureMagFilter, GLES20.GlNearest);
int numVertices = 4;
if (numVertices != QUAD_COORDS.Length / COORDS_PER_VERTEX)
{
throw new Exception("Unexpected number of vertices in BackgroundRenderer.");
}
var bbVertices = ByteBuffer.AllocateDirect(QUAD_COORDS.Length * FLOAT_SIZE);
bbVertices.Order(ByteOrder.NativeOrder());
mQuadVertices = bbVertices.AsFloatBuffer();
mQuadVertices.Put(QUAD_COORDS);
mQuadVertices.Position(0);
var bbTexCoords = ByteBuffer.AllocateDirect(numVertices * TEXCOORDS_PER_VERTEX * FLOAT_SIZE);
bbTexCoords.Order(ByteOrder.NativeOrder());
mQuadTexCoord = bbTexCoords.AsFloatBuffer();
mQuadTexCoord.Put(QUAD_TEXCOORDS);
mQuadTexCoord.Position(0);
var bbTexCoordsTransformed = ByteBuffer.AllocateDirect(numVertices * TEXCOORDS_PER_VERTEX * FLOAT_SIZE);
bbTexCoordsTransformed.Order(ByteOrder.NativeOrder());
mQuadTexCoordTransformed = bbTexCoordsTransformed.AsFloatBuffer();
int vertexShader = ShaderUtil.LoadGLShader(TAG, context,
GLES20.GlVertexShader, Resource.Raw.screenquad_vertex);
int fragmentShader = ShaderUtil.LoadGLShader(TAG, context,
GLES20.GlFragmentShader, Resource.Raw.screenquad_fragment_oes);
mQuadProgram = GLES20.GlCreateProgram();
GLES20.GlAttachShader(mQuadProgram, vertexShader);
GLES20.GlAttachShader(mQuadProgram, fragmentShader);
GLES20.GlLinkProgram(mQuadProgram);
GLES20.GlUseProgram(mQuadProgram);
ShaderUtil.CheckGLError(TAG, "Program creation");
mQuadPositionParam = GLES20.GlGetAttribLocation(mQuadProgram, "a_Position");
mQuadTexCoordParam = GLES20.GlGetAttribLocation(mQuadProgram, "a_TexCoord");
ShaderUtil.CheckGLError(TAG, "Program parameters");
}
