Texture on Texture? DX9

Im not sure what the method is called, multitexturing, texture on texture..
basically, i want to put image #1 on top of image #2 (making only the black part transparent in image #1).

this is what im using at the moment

Code:

g_Device->SetTexture(0, TextureGrass);
g_Device->SetTexture(1, TextureBlood);

g_Device->SetTextureStageState(1, D3DTSS_TEXCOORDINDEX, 0);
g_Device->SetTextureStageState(1, D3DTSS_COLOROP, D3DTOP_ADD);
g_Device->SetTextureStageState(1, D3DTSS_COLORARG1, D3DTA_CURRENT);
g_Device->SetTextureStageState(1, D3DTSS_COLORARG2, D3DTA_TEXTURE);

the result is in image #3
as you can see, the black is transparent, but it blends the other colors with the grass.
cool effect, but not what im going for.

Thanks in advance.

I would just use color-key transparency for the black color in your "1.jpg".

When i set the colorkey, it just changes the color to black, i tried changing it to green in the image and it would load it as black, not transparent.

ok, so i fixed the black part (it was showing the color i cleared to), i changed my clear color to a lightblue, and as you can see in the image, instead of showing the texture under it, it just goes through the quad.

heres the code i use

Code:

g_Device->SetTexture(0, GrassTexture);
g_Device->SetTexture(1, BloodTexture);

g_Device->SetTextureStageState(1, D3DTSS_TEXCOORDINDEX, 0);
g_Device->SetTextureStageState(1, D3DTSS_COLOROP, D3DTOP_SELECTARG1);
g_Device->SetTextureStageState(1, D3DTSS_COLORARG1, D3DTA_TEXTURE);

g_Device->SetTextureStageState(1, D3DTSS_ALPHAOP, D3DTOP_MODULATE);
g_Device->SetTextureStageState(1, D3DTSS_ALPHAARG1, D3DTA_TEXTURE);
g_Device->SetTextureStageState(1, D3DTSS_ALPHAARG2, D3DTA_CURRENT);

g_Device->SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA);
g_Device->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);

g_Device->SetRenderState(D3DRS_ALPHABLENDENABLE, true);

g_Device->DrawPrimitiveUP(D3DPT_TRIANGLESTRIP, 2, CurrentTile[x][z]);

g_Device->SetRenderState(D3DRS_ALPHABLENDENABLE, false);

and heres the image of the result:

You are forgetting about one important channel in order to do this in Direct3D. There is no color-key support in D3D but you can achieve the same effect with alpha blending.

Set the texture stage alpha blend states and it will work.

i know how its done with 1 texture, but ive never tried it with 2 textures, i did set the texture stage alpha blend states though:

Code:

g_Device->SetTextureStageState(1, D3DTSS_ALPHAOP, D3DTOP_MODULATE);
g_Device->SetTextureStageState(1, D3DTSS_ALPHAARG1, D3DTA_TEXTURE);
g_Device->SetTextureStageState(1, D3DTSS_ALPHAARG2, D3DTA_CURRENT);

do i need to set the alpha blend states for the 1st texture as well?

ive been trying for the past 2 days, using every possible combination i could think of for alpha ops and color ops.. but each time i get half of what i want done (e.g. sometimes the ENTIRE texture is transparent, sometimes the wrong half is)..

ill summarize what im trying to do:

i want to know if you can make a certain color in a texture transparent (so you can see through to the texture under it and not through the actual quad). im trying to render a quad with 2 or 3 textures and i want to overlap these textures, but leave some parts transparent to show the texture below it..

again, any help is appreciated.

thanks