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BlackJack
06-22-2002, 10:39 PM
Just a short question for which I didn't find any answer in the net and unfortunately also not on the nVidia site:

Is there any GeForce which can not do 4x multitexturing? It's some time ago since I still had the Gf 2 and the 1 I've never had, cuz I straightly hopped from TNT to Gf 2...

I need to do Basetex*Lightmap*Alphamap and the result of it blended with the framebuffer. I don't think there's any possibility to do this multipass, is there? I know I could theoretically store the alphamap in one of the other textures already, but this in my case unfortunately not possible because of performance reasons.

Michael

Zeno
06-22-2002, 11:15 PM
TNT2 - GeForce2 = 2 texture units
GeForce3 - Geforce4 = 4 texture units

You could probably do what you want multipass if you use destination alpha in the framebuffer to store your alpha texture and then apply an appropriate blending mode. It depends on the details of what you want to do.

-- Zeno

dorbie
06-23-2002, 02:56 AM
It's not clear what you need. If you mean simply multiply by an alpha term that's easy with destination alpha and another pass, and you can still blend against destination color (and write destination alpha without touching the color fragments).

BlackJack
06-23-2002, 07:53 AM
Well, there for I'd to force the user to use 24 bit colorbuffer, else I wouldn't get an alpha channel. And I don't think ubi soft would be especially pleased about that, hehe. Well... in worst case I'll store the alphamap simply within the lightmap then... problem on this is that the lightmap gets rough very quickly on distance... I hope it won't be too visible.

Because of the where for: It's for fading the landtypes in my actual landscape engine.

Michael

Zeno
06-23-2002, 11:25 PM
I'd to force the user to use 24 bit colorbuffer

32 bit you mean? Yes.


problem on this is that the lightmap gets rough very quickly on distance

I'm not sure what you mean by this, but if all you need is some generic alpha value available whenever you draw some generic pixel, what difference does it make where that alpha value comes from? Are you just saying that your lightmap is of a lower resolution than the base texture map? If so, why not store the alpha in the base texture? That would make more sense anyway, since it sounds like you're blending 1 different terrain texture on each pass...

-- Zeno

BlackJack
06-24-2002, 08:24 AM
Zeno: 32 Bit color buffer does not exist http://www.opengl.org/discussion_boards/ubb/wink.gif, the 8 bit are just the fill up, you know, alpha you can't count as color component.
How ever, nah, the problem is I can't await that everyone plays with 24 bit instead of 16, so except in textures there is no place I could store the alpha in. Well, as said, stored it in the lightmap now... is not that beauty, because of the weird resolution of it, but ok, have to survive it.

Michael

knackered
06-24-2002, 09:59 AM
Originally posted by BlackJack:
Well, there for I'd to force the user to use 24 bit colorbuffer

The alpha exists in the colour buffer, Black Jack. So you made a mistake - hope ubi soft aren't reading this, or they may panic about you! http://www.opengl.org/discussion_boards/ubb/smile.gif

BlackJack
06-24-2002, 09:40 PM
What do you mean Knackered?
You can either get 16 Bit color buffer + 16 bit depth buffer or 24 bit color, 8 bit alpha, 24 bit z and 8 bit stencil.

I know myself that the alpha is using the remaining 8 bit of the color long, if you request it, as stencil uses the remaining 8 of the depth long if you use 24 bit color depth, but this I'm not allowed to demand.

What I would need would be: 16 bit depth, 16 bit color and 8 bit alpha and this is already because of the alignment impossible. May be there's a 5-5-5-1 RGBA requestable in 16 bit color depth, but that wouldn't help me, after all it shall fade softly, not roughly from one pixel to the next.

"hope ubi soft aren't reading this, or they may panic about you" *lol* http://www.opengl.org/discussion_boards/ubb/wink.gif. Nah, as long as I won't texture the skybox with nudepics they won't worry. Since Erfurt they have anyway other things to worry about.

But how ever..... works now with help of abusing the lightmap as alphamap...

Michael