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tscott1213

Fire Effect

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Hi All, I am working on an implementation of the Vulcan Fire Effect from GPU Gems I. I have a couple of artifacts I was hoping that some of you might be able to provide some suggestions for fixing it. A demo is available here: www.tormentedgames.com\Demo.zip If you extract the files maintaining the directory structure and run the executable in the FireEffect folder, you should see the demo. (Please note this is a very early Demo and there are several bugs I have not addressed yet.) Also, note it requires DirectX and a graphics card that can handle PS 2.0 and VS 2.0. The artifacts I am trying to address are as follows: 1) Popping. The technique uses billboards and the worst visual effect is the popping as you rotate around the fire. 2) Outlines. The flames are alpha blended but some of them show some outlines. Is there some way to touch up the images in Photoshop to eliminate the outlins. (If you can't see them let me know and I will post another demo where they are more obvious.) 3) Any others you notice. Thanks for the help. I will post all of the source code, including the particle system once it is stable. I am focusing on the effect first to better understand all of the features I need to implement properly. Todd

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Looking good - runs nice and smooth (Radeon 9550).
There is a slightly odd issue I have - it looks like the flame runs an animation of a burst of flame as each sprite, but it appears that it stops then starts jerkily at one certain point (possibly related to popping?).
The outlines aren't very noticeable unless you get very close - and only really on the smoke. The flames look fine to me. [smile]

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Thanks for taking a look!

I noticed the jerkiness every so often in an earlier build but I thought I had fixed it. I'll go through the update cycle and make sure I'm not doing something funky!

Thanks again
Todd

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This fire looks better than in most of the current games :)

Concerning the popping, I don't really think you can do anything to help it when using billboards. One solution would be to render the fire warped onto, say, few cylinders one in another, to give the feeling of dense fire.

And the outlines, they don't really catch the eyes, so I wouldn't bother about it a lot.

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Quote:
Original post by MickeyMouse
This fire looks better than in most of the current games :)


Indeed it does!

The jerkiness might be related to my card (all the DX SDK demos run jerkily unless in fullscreen - as in, they run at a really high framerate then suddenly lock at a particular frame) but when I rotate the view or walk up to the fire it runs very smoothly, but the jerks in the animation are still noticeable.

But it still looks amazing [smile]

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First, thanks again for all of the feedback.

benryves: The main issue for this effect "as is" in a game is that it uses a 16MB volume texture. However, I believe that by implementing the smoke procedurally and with a change in the textures, I can get this down to 1.0MB and maybe even 512K. Procedural smoke should also improve the effect because we can use the lighting algorithm for clouds that Mark Harris(also nVidia) came up with. I am just guessing here, but the jerkiness for this demo might be due to a texture caching problem.


MickeyMouse: I'll experiment with that suggestion, thats a good idea. I am also looking at using a cross or star configuration for the billboards like they did in the grass demo in GPU Gems. The issue with that method is the alpha blending with z-order turned on.

This discussion really helps me focus on what I need to do next.
So thank you.
Todd

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But,....you should not forget about great (animated) fire texture used in the demo. Without cool art work, even best technology would seem crappy ;)

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Quote:
Original post by tscott1213
I am also looking at using a cross or star configuration for the billboards like they did in the grass demo in GPU Gems. The issue with that method is the alpha blending with z-order turned on.


Concerning cross - instead of 2 quads crossing in the middle, you can break each of them into 2 quads right along the crossing line (resulting in 4 quads). Doing so, you can z-sort your 4 quads and the problems with z-order will be gone. The same applies to stars.

With the grass demo (I didn't see it) I suspect such partitioning would result in a lot more geometry and might turn inpractical, because the grass quads probably intersect at very many points (meaning lines).

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