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i3d artefacts


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Original was:

Good day!

I have set a pipeline as described at video tutorials for acheiving some volumetric fx - everything working fine, excluding one BIG problem - there are a lot of artefacts - and as I've found - they are regular artefacts - it looks like noisy bounds of volume "buckets" - noisy planes evenly placed at any spaces direction and they are visible where density is present. It is VERY sadly, and made this technique almost unusable.

What about trying avoid this: I try to make oversampling more, than 1 - I acheiving only splitting of that "planes", not eliminating of them. Varying of "Variance" has no effects at all, excluding crazy blur at 0.9-1.0 values, without eliminating of main artefacts. Does anyone know, what I have to do to fight with it, or it is core technology problem?

hip-file, images or mov - on request - welcome!

Thank you.

RenderNode: ASUS PE851, P IV 2.6 GHz HT, 1Gb RAM, MSI GeForce FX 5600, WinXP sp 1

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Next series of testing have opened these features - artifacts appear at boundaries of volume tiles of 32x32x32 voxels - they looks like swapped voxel layers of adjacend "tiles". I have a suggestion about that there are such organization of i3d texture, because i3dinfo utility says about this quantity of 32s at each dimension as "tile counts".

May anyone say something about this?

image of tragedy : just sections of 3d texture (simple noise) attached


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  • 2 months later...

Hmmm, yes, I've seen these as well on any i3D volume gag that gets close to the camera. It's almost like seeing a 3D version of JPEG/MPEG artifacts. Unfortunately I don't know how to get around it. I've seen it sometimes more, sometimes less, when rendering with and without adaptive sampling in the cloud shader calling the i3d texture.

My guess is it's being introduced by 'i3dgen' which, last time I looked, hadn't been touched since around build 2.53 or so of Houdini 5. It's a marginally functional program that's called by the i3d ROP and is prone to all sorts of problems, crashing and is limited to generating fairly low density divisions in your texture. It's also almost undocumented, last time I looked. But at least they fixed its tendency to randomly jumble voxels along the bounds of the space you were sampling. That was fun.

I don't want to be a party pooper, but I really wish SESI had concentrated on making i3D more of a priority over the last couple years. It's a lot more useful to a majority of their customer base than beefed up character tools. Just sayin'. Maybe then the guys at Sony wouldn't be making new Houdini cogs run through their awful Spiderman FX tutorial where they attach a particularly hideous Renderman noise shader to spheres copied to particles...kinda like we all had to do it back in the '90s


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these artifacts are known by sesi and have been fixed i believe..

but there has been a lot of talk about this... search the threads here, at sesi, and in the mail archives for the list serv...

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