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Volume Implicit Field to PRman


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Hi!

I want to write an implicit field plugin for PRMan which should load a Houdini cached fluid box and make the voxel data available to the renderer. I couldn't find much about .sim/.bgeo file formats in the HDK, although I don't think these are the right cache files for this purpose since they don't purely represent a fluid cache, but also other simdata/geo. Maybe someone can help me with this?

Thanks,

Phong

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Write out a .geo file of your volume primitives. The .geo/.bgeo file format is documented in $HFS/houdini/public/GPD/GPD.txt

Does this document describe volume primitive? I thought it's not (can't check it now). So either one has to make prman plugin dependent on HDK, or use other format (like field3d), hasn't he?

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not sure if you know this already but you don't necessarily have to write a plugin or use any custom formats to do this. the utility 'hbrickmap' makes a brickmap volume prim out of a .bgeo volume. it makes rendering houdini volumes in prman an out-of-the-box capability (and it works quite well).

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Does this document describe volume primitive? I thought it's not (can't check it now).

Yes, it does. I know of at least one studio who has successfully implemented it into their in-house version of GPD. But I didn't know about hbrickmap so that's probably the best solution by far. :)

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  • 2 weeks later...

Ok, thank you very much for your replies!

I indeed tried the hbrickmap tool first and preferred to avoid it for the purpose of transferring houdini volume data to prman because of the following reasons:

1. Just because of its nature, it is a lossy process (.geo -> point-cloud -> brickmap) for which especially a lot of data get lost at the brickmap generation process

2. I cannot feed the brickmap with custom data that I'd like to add, or I haven't figured out how

3. difficult to control how much detail remains in the brickmap (-maxerror doesn't seem to make a big difference)

And for some reason my volume box doesn't look right when converted to brickmap. Very blocky and very low resolution. Has anyone achieved good results with hbrickmap and volumes??

Thanks,

Phong

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And how can I create a brickmap with world-space rastering? All my brickmaps get offset.

I looked through the docs concerning volume primitives and couldn't find anything about it. Looking at an ascii .geo file, I see a lot of float values for the volume primitive which I'd like to decipher. So if anyone knows more about this, he's more than welcome to post anything :)

Cheers,

Nhat

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