Alpha mode

[Crystal Noir]

Hello all,

I've got a little problem....

I understand that :

- If I want a sprite with an alpha add I have to set up the drawing mode with 2+16
- If I want a sprite with an alpha level (for transparency/intensity) I have to set up the drawing mode with 2+4
- If I want to play with color, I have to set up the drawing mode with 2+4096

But...

If I want a sprite with all of these, How can I do it ??

If I want a sprite with alpha level (to play with intensity/transparency), alpha add, to simulate lightning and play with color ?

I tried 2+16+4096 but it doesn't work :D

Got an idea ?

Thx in advance.

[thaaks]

That's exactly what I struggled with in my testcase for your "Lighting" thread with the candle demo!

I got the impression that it's not working although combinations (alpha add plus slowly alpha fading) would be great and looking at those power of 2 constants it could work.

Kevin: Does it? Should it?

[kevin]

You can't combine more than a pair of draw modes.. It generates too much code :)

So you want to  add a constant color to the src pixels, then add the result to the destination buffer ?

ie.

  SrcPixel=SrcPixel+Colour

  DestPixel=DestPixel+SrcPixel

[Crystal Noir]

yes but if we want to scale a sprite + set a different color + have a simulated light (add), + alpha channel transparency we can't if I understand...

Your idea is good for the color, but I have the same pb with add and alpha transparency....

Look at my candle (first post with my Zip file), I can combine all of these :) I use an alpha add only but I can set up alpha transparency and vectors color of the 3D sprite at the same time :)

I don't understand how I can do this here.

[kevin]

  PB1.63  doesn't have "3D sprites"   see FAQ

[Crystal Noir]

I already know that, I mean, the question is : Is it possible with the 1.70 version so ? ;) (I don't have precise it)

[kevin]

It's possible in both :)

[Crystal Noir]

ok but how ? I would like to have these 3 effects at the same time.

[kevin]

  Vertex colouring simply multiples the current texel (src pixel) with the interpolated vertex colours in texture space.   If  they (vertex colours) are all the same then it's just multiplying the a constant colour with the source texel.    You can simulate this by simply premultiing the texture.  Then the render only has to fetch and add the pixels together (src + dest),   rather than interploate/fetch/multply/add.  So the cost per pixel is lower.

   See BlitImageAlphaMult.