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Drawing a decal

Started by Sfpiano Dec 31, 2003 at 7:26 PM 2 replies 550+ views

Original Post

Dec 31, 2003 at 7:26 PM

I''m trying to add a decal texture on top of my terrain but am running into some difficulties. I tried simply using this code:

pDevice->SetTexture(1, p_BulletTex);
		pDevice->SetStreamSource(1, pBulletVB, 0, sizeof(TERRAINVERTEX));
		pDevice->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 2);

but as you can imagine it didn''t work. I keep reading about multi-texturing, but everything I''ve come across involves blending two textures together, which isn''t what I want. //------------------------------------------------------------------------------------------------------ The great logician Bertrand Russell once claimed that he could prove anything if given that 1+1=1. So one day, some fool asked him, "Ok. Prove that you''re the Pope." He thought for a while and proclaimed, "I am one. The Pope is one. Therefore, the Pope and I are one."

curtmax_0

Jan 1, 2004 at 3:06 AM

You don''t have to use modulate to blend textures together... you can use an add operation.... that would probably be better for a decal...

Sfpiano

Jan 1, 2004 at 12:40 PM

Hmm, ok I''ll look into that. But I''ve been thinking that the way I''ve conceived it, everytime I want to add a decal, or a different type of decal, I need a new vertex buffer, and a new stream source, and a new texture. There has to be a better way of doing this; can I avoid this using stencil buffers?

Sfpiano

Jan 2, 2004 at 12:08 AM

From what I''ve read stencil buffers seem like a good way to render decals; the problem is I''m confused on how to set them up. The way I have it set up is this: turn off z, turn on stencil, then set up stencil buffer:


pDevice->SetRenderState( D3DRS_STENCILFUNC,  D3DCMP_ALWAYS );
    pDevice->SetRenderState( D3DRS_STENCILZFAIL, D3DSTENCILOP_KEEP );

    // If ztest passes, inc/decrement stencil buffer value
    pDevice->SetRenderState( D3DRS_STENCILREF,       0x1 );
    pDevice->SetRenderState( D3DRS_STENCILMASK,      0xffffffff );
    pDevice->SetRenderState( D3DRS_STENCILWRITEMASK, 0xffffffff );
    pDevice->SetRenderState( D3DRS_STENCILPASS,      D3DSTENCILOP_INCR );

Then I render the data which contains the vertex coorinates for the decal. After that I set up texture stages and do this:


pDevice->SetRenderState( D3DRS_STENCILREF,  0x1 );
    pDevice->SetRenderState( D3DRS_STENCILFUNC, D3DCMP_LESSEQUAL );
    pDevice->SetRenderState( D3DRS_STENCILPASS, D3DSTENCILOP_KEEP );

and then render the decal data. I really haven''t found any good explanations of the code behind stencil buffering, and am basically just throwing SDK code around and crossing my fingers. :-|

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