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Multiply Alpha Blend?

Started by cow_in_the_well Jul 11, 2004 at 7:14 AM 2 replies 2k views

Original Post

116

Jul 11, 2004 at 7:14 AM

I have a feeling taht the answer will be "NOS!", but is there a way to set up d3d alpha blending to do a multiply between src and dest? Basically, i want to do something like finalcolor = src * dest. Yes? No? Or No :(?

Kibble

Jul 11, 2004 at 7:23 AM

Yes, its a bit tricky though. You'll notice that some of the options for blend weights is src, and dest. so:

SetRenderState(D3DRS_DESTBLEND, D3DBLEND_SRCCOLOR);SetRenderState(D3DRS_SRCBLEND, D3DBLEND_ZERO);

or if you want modulate 2x:

SetRenderState(D3DRS_DESTBLEND, D3DBLEND_SRCCOLOR);SetRenderState(D3DRS_SRCBLEND, D3DBLEND_DESTCOLOR);

cow_in_the_well

Author

116

cow_in_the_well

Jul 11, 2004 at 7:34 AM

OH! YES! Thank you :). I didn't think to try sticking the srccolor into the dest blend :).

My light rendering system is working nicely now kthx.

Kibble

Jul 11, 2004 at 12:37 PM

No problem, this took me a long time to find out when I was looking to do some multipass modulating :)

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