/// <summary>
/// Draw geometry by indexing into the vertex buffer.
/// </summary>
/// <param name="primitiveType">The type of primitives in the index buffer.</param>
/// <param name="baseVertex">
/// Used to offset the vertex range indexed from the vertex buffer.
/// </param>
/// <param name="minVertexIndex">
/// A hint of the lowest vertex indexed relative to baseVertex.
/// </param>
/// <param name="numVertices">An hint of the maximum vertex indexed.</param>
/// <param name="startIndex">
/// The index within the index buffer to start drawing from.
/// </param>
/// <param name="primitiveCount">
/// The number of primitives to render from the index buffer.
/// </param>
/// <remarks>
/// Note that minVertexIndex and numVertices are unused in MonoGame and will be ignored.
/// </remarks>
public void DrawIndexedPrimitives(
PrimitiveType primitiveType,
int baseVertex,
int minVertexIndex,
int numVertices,
int startIndex,
int primitiveCount
)
{
// Flush the GL state before moving on!
ApplyState();
// Unsigned short or unsigned int?
bool shortIndices = Indices.IndexElementSize == IndexElementSize.SixteenBits;
// Set up the vertex buffers.
for (int i = 0; i < vertexBufferCount; i += 1)
{
GLDevice.BindVertexBuffer(
vertexBufferBindings[i].VertexBuffer.Handle
);
vertexBufferBindings[i].VertexBuffer.VertexDeclaration.Apply(
VertexShader,
(IntPtr)(
vertexBufferBindings[i].VertexBuffer.VertexDeclaration.VertexStride *
(vertexBufferBindings[i].VertexOffset + baseVertex)
)
);
}
// Enable the appropriate vertex attributes.
GLDevice.FlushGLVertexAttributes();
// Bind the index buffer
GLDevice.BindIndexBuffer(Indices.Handle);
// Draw!
GLDevice.glDrawElements(
PrimitiveTypeGL(primitiveType),
//minVertexIndex,
//minVertexIndex + numVertices - 1,
GetElementCountArray(primitiveType, primitiveCount),
shortIndices ?
OpenGLDevice.GLenum.GL_UNSIGNED_SHORT :
OpenGLDevice.GLenum.GL_UNSIGNED_INT,
(startIndex * (shortIndices ? 2 : 4))
);
}
