/**
* Creates and initializes OpenGL resources needed for rendering the model.
*
* @param context Context for loading the shader and below-named model and texture assets.
* @param objAssetName Name of the OBJ file containing the model geometry.
* @param diffuseTextureAssetName Name of the PNG file containing the diffuse texture map.
*/
public void CreateOnGlThread(Context context, string objAssetName, string diffuseTextureAssetName)
{
// Read the texture.
var textureBitmap = BitmapFactory.DecodeStream(context.Assets.Open(diffuseTextureAssetName));
GLES20.GlActiveTexture(GLES20.GlTexture0);
GLES20.GlGenTextures(mTextures.Length, mTextures, 0);
GLES20.GlBindTexture(GLES20.GlTexture2d, mTextures[0]);
GLES20.GlTexParameteri(GLES20.GlTexture2d,
GLES20.GlTextureMinFilter, GLES20.GlLinearMipmapLinear);
GLES20.GlTexParameteri(GLES20.GlTexture2d,
GLES20.GlTextureMagFilter, GLES20.GlLinear);
GLUtils.TexImage2D(GLES20.GlTexture2d, 0, textureBitmap, 0);
GLES20.GlGenerateMipmap(GLES20.GlTexture2d);
GLES20.GlBindTexture(GLES20.GlTexture2d, 0);
textureBitmap.Recycle();
ShaderUtil.CheckGLError(TAG, "Texture loading");
// Read the obj file.
var objInputStream = context.Assets.Open(objAssetName);
var obj = ObjReader.Read(objInputStream);
// Prepare the Obj so that its structure is suitable for
// rendering with OpenGL:
// 1. Triangulate it
// 2. Make sure that texture coordinates are not ambiguous
// 3. Make sure that normals are not ambiguous
// 4. Convert it to single-indexed data
obj = ObjUtils.ConvertToRenderable(obj);
// OpenGL does not use Java arrays. ByteBuffers are used instead to provide data in a format
// that OpenGL understands.
// Obtain the data from the OBJ, as direct buffers:
IntBuffer wideIndices = ObjData.GetFaceVertexIndices(obj, 3);
FloatBuffer vertices = ObjData.GetVertices(obj);
FloatBuffer texCoords = ObjData.GetTexCoords(obj, 2);
FloatBuffer normals = ObjData.GetNormals(obj);
// Convert int indices to shorts for GL ES 2.0 compatibility
ShortBuffer indices = ByteBuffer.AllocateDirect(2 * wideIndices.Limit())
.Order(ByteOrder.NativeOrder()).AsShortBuffer();
while (wideIndices.HasRemaining)
{
indices.Put((short)wideIndices.Get());
}
indices.Rewind();
var buffers = new int[2];
GLES20.GlGenBuffers(2, buffers, 0);
mVertexBufferId = buffers[0];
mIndexBufferId = buffers[1];
// Load vertex buffer
mVerticesBaseAddress = 0;
mTexCoordsBaseAddress = mVerticesBaseAddress + 4 * vertices.Limit();
mNormalsBaseAddress = mTexCoordsBaseAddress + 4 * texCoords.Limit();
int totalBytes = mNormalsBaseAddress + 4 * normals.Limit();
GLES20.GlBindBuffer(GLES20.GlArrayBuffer, mVertexBufferId);
GLES20.GlBufferData(GLES20.GlArrayBuffer, totalBytes, null, GLES20.GlStaticDraw);
GLES20.GlBufferSubData(
GLES20.GlArrayBuffer, mVerticesBaseAddress, 4 * vertices.Limit(), vertices);
GLES20.GlBufferSubData(
GLES20.GlArrayBuffer, mTexCoordsBaseAddress, 4 * texCoords.Limit(), texCoords);
GLES20.GlBufferSubData(
GLES20.GlArrayBuffer, mNormalsBaseAddress, 4 * normals.Limit(), normals);
GLES20.GlBindBuffer(GLES20.GlArrayBuffer, 0);
// Load index buffer
GLES20.GlBindBuffer(GLES20.GlElementArrayBuffer, mIndexBufferId);
mIndexCount = indices.Limit();
GLES20.GlBufferData(
GLES20.GlElementArrayBuffer, 2 * mIndexCount, indices, GLES20.GlStaticDraw);
GLES20.GlBindBuffer(GLES20.GlElementArrayBuffer, 0);
ShaderUtil.CheckGLError(TAG, "OBJ buffer load");
int vertexShader = ShaderUtil.LoadGLShader(TAG, context,
GLES20.GlVertexShader, Resource.Raw.object_vertex);
int fragmentShader = ShaderUtil.LoadGLShader(TAG, context,
GLES20.GlFragmentShader, Resource.Raw.object_fragment);
mProgram = GLES20.GlCreateProgram();
GLES20.GlAttachShader(mProgram, vertexShader);
GLES20.GlAttachShader(mProgram, fragmentShader);
GLES20.GlLinkProgram(mProgram);
GLES20.GlUseProgram(mProgram);
ShaderUtil.CheckGLError(TAG, "Program creation");
mModelViewUniform = GLES20.GlGetUniformLocation(mProgram, "u_ModelView");
mModelViewProjectionUniform =
GLES20.GlGetUniformLocation(mProgram, "u_ModelViewProjection");
mPositionAttribute = GLES20.GlGetAttribLocation(mProgram, "a_Position");
mNormalAttribute = GLES20.GlGetAttribLocation(mProgram, "a_Normal");
mTexCoordAttribute = GLES20.GlGetAttribLocation(mProgram, "a_TexCoord");
mTextureUniform = GLES20.GlGetUniformLocation(mProgram, "u_Texture");
mLightingParametersUniform = GLES20.GlGetUniformLocation(mProgram, "u_LightingParameters");
mMaterialParametersUniform = GLES20.GlGetUniformLocation(mProgram, "u_MaterialParameters");
ShaderUtil.CheckGLError(TAG, "Program parameters");
Android.Opengl.Matrix.SetIdentityM(mModelMatrix, 0);
}