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Old 24-09-2005, 03:34 PM   #1
Velusion
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Default Voxels problem

Hey! I haven't posted in a while but I've been busy trying to learn new things with Maya.

I'm working on a meteor that has crashed throught the atmosphere and is falling to Earth (like Deep Impact) All is well with my meteor and the exhaust trail except that the rendering is blocky and when you watch it one frame at a time, you can see what appears to be voxels filling up until they are full. After that they seem to spill over into the next voxel. My voxel resolution is very high so I don't know what is happening. I tried everything I could think of. I turned down the density to almost nothing but the blockiness remains. The surface attribute for the fluid is set to Volume Render.

Here is a frame from the video test that shows the problem.





Any and all help will be appreciated in solving this problem.
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Old 24-09-2005, 10:23 PM   #2
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Ok, check my new tips site for a few tips that might help your situation:

http://www.ragecg.com/public/ragecgt...id_tips01.html
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Old 26-09-2005, 10:24 AM   #3
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I know you said your resolution is high, but bear with me.... also I'm not sure if this is a 2D or 3D container too so...

I can tell you just by looking at this that your resolution definitly has something to do with this.. the fluid is going to spill into other voxels no matter what, your resolution, on top of things, can make you or break you when it comes to making it look good. Another thing that you want to mess with is your opacity graph, that goes hand in hand with your container's resolution, especially if you scaled the fluid container in the scene and not in the attribute editor.

The effect your going for in that particular scene is going to require some fine detail, as you can tell.

I would have to see the scene to troubleshoot this, but looking at it, try this....

If its a 2D container, pump that resolution up very very high, and I'm talking at the very least twice as much as you would with a 3d container, you can still sim the fluids very well with an extremely high resolution on a 2D container, especially for that effect.

If its a 3D container, then the most you want your resolution for this effect is a 3 to 1 ratio meaning for every 1 unit you want 3x the resolution, example of that is if my fluid container is 10x10x10 then I want my resolution 30x30x30...
anything higher for this you're killing and wasting resources like a bad farmer....

Now for the piece that definitly plays a huge role...

Your opacity graph will play as much a role here if not more than your resolution. This isn't fire, so from left to right your opacity should be 0 to 1, to give you a start, your first point should be about .1 in the selected position and 0 for your value.. start with that, and make several other points leading up to 1 in position and 1 in value.

One other thing you might want to look at too...

I'm assuming you're using textures, so look at your texture scale that may have an effect also if the texture scales are bigger than 1
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Old 26-09-2005, 01:23 PM   #4
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Thanks for the great advice, guys.

It was indeed a resolution problem after all. My 3D container was 300 x 20 x 20 and the resolution was 100 x 16 x 16 which seemed like a lot but, relatively speaking, was very low. My plan is to make the container much smaller (80 x 20 x 20) with a 3x resolution. I will animate the movement of the container as the meteor moves.

I'll post the results soon.
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Old 26-09-2005, 05:10 PM   #5
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make sure you cache your fluids after you animate the container..... otherwise you'll get a lot of jittering and popping going on in playback and thats not good


EDIT: hah I spelled cache cash.. don't mind me I just woke up
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Old 26-09-2005, 05:43 PM   #6
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Razor,
The thing is that the meteor has to travel a great distance and the exhaust trail is pretty long before I have it begin dissipating. Unless you can suggest something, the two possibilities I can think if would be to: 1- have a really big fluid container or 2- animate a smaller container to fly along with the meteor and it's tail. To be honest, I haven't tried the "flying container" idea yet but I never considered that by moving it, I'm also moving the position of each voxel. I can understand how that could cause visual changes. :headbang:
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Last edited by Velusion : 26-09-2005 at 07:44 PM.
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Old 26-09-2005, 06:18 PM   #7
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or 3, make the container one size and use particles cloud for your smoke trail with a volume sphere emitter(s)=D

You can animate the fluid container intself, and thinking about this project its a really bad idea in your case to change the size in animation unless you can do it like alias can....

there is an example in the visor where they did a nuke and they animated the size of the container... I don't like it personally I can just make one size and get the same result with less hassle....

also one other thing you absolutely have to make sure, and that is you play every frame, you can set this in your preferences...

now, with just one size and an animated fluid container add the smoke trails with particles using clouds.... will give you a much much faster result as well and with compositing you can put everything together and make it look just as good...

Now, you also have to key the rotation of the fluid container, so instead of Y pointing up, Y should be pointing in the direction its coming from IE if your fireball is traveling in +Z then +Y should be pointing in -Z

Hope this helps... I would love to see this project when its completed...
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Old 26-09-2005, 07:47 PM   #8
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Hopefully by Friday. :attn:
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Old 26-09-2005, 08:20 PM   #9
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glad you got it fixed!

Thanks for the help Raz!
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Old 28-09-2005, 04:04 PM   #10
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Here are a couple of test renderings of my new and improved meteor.

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Old 28-09-2005, 06:11 PM   #11
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the first image is more along the lines of what I would imagine a blazing fireball/meteor would be

so tell us how you did it
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Old 28-09-2005, 08:17 PM   #12
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Hello,

is it possible to post a scene file of your meteor ?



thx
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Old 28-09-2005, 10:07 PM   #13
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Yes. I will post the file as soon as I'm through tweeking it. Please give me a couple of days.
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