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Is Volume Fog Broken, Or Is Just A User Error?


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#1 oesponda

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Posted 25 September 2013 - 11:33 PM

Hello everyone,


First of all I declare myself totally noob in this matter, used volume mask looong ago and haven't used it (nor volume fog) for a while.

I was trying to add volume fog to a comp I've been working on, and I couldn't get it to work. After lots of tries I thought my world position pass was somehow broken, tried several things but the results were always wrong. Then I decided to give volume mask a try, just to be sure my wpp was not working, and guess what? It actually worked! volume mask reads wpp as expected and the mask behaves as expected. Maybe I'm doing something completely wrong, but this makes me think volume fog is broken, not so volume mask.

The second problem I have is with the external image to control the volume... no matter what, I always get errors from both tools... Again, I'm a noob but followed the tooltorial on eyeon's youtube channel, step by step, and simply couldn't get it to work.

If any of you have some expirience and want to share a couple of tricks/advices, I would really appreciate it.


Here a quick video showing what I tried to describe above... http://www.screencast.com/t/0S7f2eYwP



Thanks in advance,
Orlando.

#2 SecondMan

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Posted 26 September 2013 - 12:23 AM

Hey Orlando,


Volume Fog can be a bit tricky to get to work, true. Some of the settings make my head spin too :)

You can find a volume fog setup in here, actually, if you want to take a look: http://www.pigsfly.c...t=30#entry37571

Perhaps that gives you some hints...

Otherwise, is there a chance you can upload an image and your setup so we could take a look? Would definitely be easier...

Cheers,
Pieter

#3 isotron

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Posted 26 September 2013 - 03:15 AM

this is because your sclices are set to 256! That means, your fog at frame 0 need the fastnoise form 0-256. so u need to expand your comp-range.

#4 bfloch

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Posted 26 September 2013 - 08:18 AM

isotron is right. The source range is the most common problem.

Since VolumeFog uses the time to store the third dimension (one frame is one slice) you need to make sure it does not run dry.

#5 oesponda

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Posted 26 September 2013 - 01:03 PM

Right, thanks guys.

The texture problem is fixed now :)

However the mask behavior problem remains: volume mask seems to behave ok and the shapes is well defined. On the other hand, volume fog seems to be distorted and behaving very odd.

http://www.screencast.com/t/Ydp4r0KVxl

Any idea of why is this?


Pieter, will take a look at the link you posted, thanks. Unfortunately I can't share these files at least for now, but if I have time, will try to reproduce the issue with a simple scene.


Thanks for your feedback guys.

#6 French_Fry

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Posted 26 September 2013 - 01:22 PM

It seems like I've had that problem before....just can remember what the issue was. Is the WPP 32 bit exr?

#7 oesponda

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Posted 26 September 2013 - 05:25 PM

Yes Joel, tried with 32 and 16 bits exr, same result with both. Any other idea?

Thanks,
Orlando.

#8 oesponda

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Posted 26 September 2013 - 07:27 PM

Found it, when I imported my camera, I used a scale factor (and forgot about it), so the solution is to scale the channels of the WPP by the same factor, or re import the camera with the original scale.

Hope this helps someone in the future.


Thanks everyone,
Orlando.




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