Multitexturing and lighting problem.

My question is to do with a multitexturing problem in directx. I've searched all over the place and come up a blank with it, so here it is... Basically, i'm trying to render a polygon that has two textures which are blended using vertex alpha components. I'd like to do it using 2 texture units if possible, but I can't figure it out. The problem is that that both of the textures need to be modulated with the diffuse color (lighting) for the final result to be correct. Alternatively I can blend between the two textures and then modulate with the diffuse color, but it requires the use of a 3rd texture unit =/ These are the texture stage states for the 3 texture unit version... Texture A is in unit 0. Texture B is in unit 1. No texture in unit 2.


// Stage 0 : Select the color from texture A and the alpha from the vertex diffuse component

        pD3D->pDevice->SetTextureStageState(0, D3DTSS_COLOROP, D3DTOP_SELECTARG1);
        pD3D->pDevice->SetTextureStageState(0, D3DTSS_COLORARG1, D3DTA_TEXTURE);
        pD3D->pDevice->SetTextureStageState(0, D3DTSS_ALPHAOP, D3DTOP_SELECTARG1);
        pD3D->pDevice->SetTextureStageState(0, D3DTSS_ALPHAARG1, D3DTA_DIFFUSE);

// Stage 1 : Blend between the color from stage 0 (texture A) and the color from texture b, using the alpha from stage 0

        pD3D->pDevice->SetTextureStageState(1, D3DTSS_COLOROP, D3DTOP_BLENDCURRENTALPHA);
        pD3D->pDevice->SetTextureStageState(1, D3DTSS_COLORARG1, D3DTA_TEXTURE);
        pD3D->pDevice->SetTextureStageState(1, D3DTSS_COLORARG2, D3DTA_CURRENT);
        pD3D->pDevice->SetTextureStageState(1, D3DTSS_ALPHAOP, D3DTOP_DISABLE);

// Stage 2 : Modulate the result by the diffuse color (from lighting)

        pD3D->pDevice->SetTextureStageState(2, D3DTSS_COLOROP, D3DTOP_MODULATE);
        pD3D->pDevice->SetTextureStageState(2, D3DTSS_COLORARG1, D3DTA_CURRENT);
        pD3D->pDevice->SetTextureStageState(2, D3DTSS_COLORARG2, D3DTA_DIFFUSE);
        pD3D->pDevice->SetTextureStageState(2, D3DTSS_ALPHAOP, D3DTOP_DISABLE);

Using 2 texture unit, the closest I have been able to get is this... Texture A is in unit 0. Texture B is in unit 1.


// Stage 0 : Modulate texture A's color by the diffuse vertex color (from lighting). Select the alpha from the diffuse component.

pD3D->pDevice->SetTextureStageState(0, D3DTSS_COLOROP, D3DTOP_MODULATE);
        pD3D->pDevice->SetTextureStageState(0, D3DTSS_COLORARG1, D3DTA_DIFFUSE);
        pD3D->pDevice->SetTextureStageState(0, D3DTSS_COLORARG2, D3DTA_TEXTURE);
        pD3D->pDevice->SetTextureStageState(0, D3DTSS_ALPHAOP, D3DTOP_SELECTARG1);
        pD3D->pDevice->SetTextureStageState(0, D3DTSS_ALPHAARG1, D3DTA_DIFFUSE);

// Stage 1 : Blend between the color from the previous stage and the color from texture B, using the alpha from the previous stage

        pD3D->pDevice->SetTextureStageState(1, D3DTSS_COLOROP, D3DTOP_BLENDCURRENTALPHA);
        pD3D->pDevice->SetTextureStageState(1, D3DTSS_COLORARG1, D3DTA_TEXTURE);
        pD3D->pDevice->SetTextureStageState(1, D3DTSS_COLORARG2, D3DTA_CURRENT);
        pD3D->pDevice->SetTextureStageState(1, D3DTSS_ALPHAOP, D3DTOP_DISABLE);

This gives incorrect results as only texture A has the effect of lighting applied to it. Is there some weird combination of texture stage states that will do the job in two, or am i stuck having to use a 3rd unit to get it done in one pass? [edited by - Vaalean on January 31, 2004 8:12:28 PM]

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