GL_ARB_depth_texture http://www.opengl.org/registry/specs/gl/ARB/depth_texture.txt GL_ARB_depth_texture GL_DEPTH_COMPONENT16_ARB 0x81A5 GL_DEPTH_COMPONENT24_ARB 0x81A6 GL_DEPTH_COMPONENT32_ARB 0x81A7 GL_TEXTURE_DEPTH_SIZE_ARB 0x884A GL_DEPTH_TEXTURE_MODE_ARB 0x884B