Game Development Reference
In-Depth Information
if (m_MeshHasNormals)
{
// Set up Vertex Texture Data stream to shader
m_VertexBuffer.position(m_MeshVerticesDataNormalOffset);
GLES20.glVertexAttribPointer(NormalHandle, 3, GLES20.GL_FLOAT, false,
m_MeshVerticesDataStrideBytes, m_VertexBuffer);
GLES20.glEnableVertexAttribArray(NormalHandle);
}
}
The
DrawMesh()
function in Listing 4-35 first calls the
SetUpMeshArrays()
function to prepare the
vertex attributes for sending to the shader.
Listing 4-35. Main Drawing Function DrawMesh
void DrawMesh(int PosHandle, int TexHandle, int NormalHandle)
{
SetUpMeshArrays(PosHandle, TexHandle, NormalHandle);
GLES20.glDrawElements(GLES20.GL_TRIANGLES, m_DrawListBuffer.capacity(),
GLES20.GL_UNSIGNED_SHORT, m_DrawListBuffer);
// Disable vertex array
GLES20.glDisableVertexAttribArray(PosHandle);
CheckGLError("glDisableVertexAttribArray ERROR - PosHandle");
if (m_MeshHasUV)
{
GLES20.glDisableVertexAttribArray(TexHandle);
CheckGLError("glDisableVertexAttribArray ERROR - TexHandle");
}
if (m_MeshHasNormals)
{
GLES20.glDisableVertexAttribArray(NormalHandle);
CheckGLError("glDisableVertexAttribArray ERROR - NormalHandle");
}
}
Next, the
glDrawElements()
function is called with the following parameters:
Primitive drawing type, which is
GL_TRIANGLES
1.
2.
The number of vertex indices to be processed
The type of the vertex index, which is
GL_UNSIGNED_SHORT
3.
4. The buffer that contains the vertex indices to process, which is
m_DrawListBuffer
Finally, each vertex attribute that was activated is now disabled with the
glDisableVertexAttribArray()
function. The
CheckGLError()
function is also called to check to see if any OpenGL errors have
occurred.
