public void DrawIndexed(int startIndex, int indexCount, int baseVertex)
{
PreDraw(baseVertex);
var effectiveOffset = indexOffset + startIndex * indexFormat.GetSize();
GL.DrawElements(
(PrimitiveType)GLHelper.GetGLPrimitiveType(primitiveTopology), indexCount,
(DrawElementsType)GLHelper.GetGLDrawElementsType(indexFormat), new IntPtr(effectiveOffset));
GLHelper.CheckGLErrors();
}