SDK documentation offers this code to set up texture stages when doing bump mapping: // Set the color operations and arguments to prepare for // bump mapping. // Stage 0: The base texture d3dDevice->SetTextureStageState( 0, D3DTSS_COLOROP, D3DTOP_MODULATE ); d3dDevice->SetTextureStageState( 0, D3DTSS_COLORARG1, D3DTA_TEXTURE ); d3dDevice->SetTextureStageState( 0, D3DTSS_COLORARG2, D3DTA_DIFFUSE ); d3dDevice->SetTextureStageState( 0, D3DTSS_ALPHAOP, D3DTOP_SELECTARG1 ); d3dDevice->SetTextureStageState( 0, D3DTSS_ALPHAARG1, D3DTA_TEXTURE ); d3dDevice->SetTextureStageState( 0, D3DTSS_TEXCOORDINDEX, 1 ); // Stage 1: The bump map - Use luminance for this example. d3dDevice->SetTextureStageState( 1, D3DTSS_TEXCOORDINDEX, 1 ); d3dDevice->SetTextureStageState( 1, D3DTSS_COLOROP, D3DTOP_BUMPENVMAPLUMINANCE); d3dDevice->SetTextureStageState( 1, D3DTSS_COLORARG1, D3DTA_TEXTURE ); d3dDevice->SetTextureStageState( 1, D3DTSS_COLORARG2, D3DTA_CURRENT ); // Stage 2: A specular environment map d3dDevice->SetTextureStageState( 2, D3DTSS_TEXCOORDINDEX, 0 ); d3dDevice->SetTextureStageState( 2, D3DTSS_COLOROP, D3DTOP_ADD ); d3dDevice->SetTextureStageState( 2, D3DTSS_COLORARG1, D3DTA_TEXTURE ); d3dDevice->SetTextureStageState( 2, D3DTSS_COLORARG2, D3DTA_CURRENT ); As far as I understand, it assumes that FVF must be something like this: struct BUMPVERTEX { D3DXVECTOR3 p; D3DXVECTOR3 n; FLOAT tu1, tv1; FLOAT tu2, tv2; } My question is: how should I set the second set of texture coordinates when loading model from X-file? Should both coordinate sets be the same? Why should I use two sets of texture coordinates at all? Thank you