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Technical Discussion » IOR vs Reflectivity ? Transparency vs Opacity?
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- jpparkeramnh
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The way I see opacity, is that it is a rendering shortcut for materials that are assumed to have holes in them that are too small too see. The amount of opacity is inverse to the porousness of the surface / volume.
Technical Discussion » Gradient Fall-off Volume
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- jpparkeramnh
- 178 posts
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tapoh
thanks! and how this can be achieved along all three axes x,y,z?
Without testing, probably like:
@density = 1 - length(relbbox(@P));
Technical Discussion » Fastest way to write data out of node?
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- jpparkeramnh
- 178 posts
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I assume you need the individual curves to be known… otherwise you can grab an entire attribute efficiently using functions like this one:
http://www.sidefx.com/docs/houdini/hom/hou/Geometry.html#pointFloatAttribValuesAsString [www.sidefx.com]
http://www.sidefx.com/docs/houdini/hom/hou/Geometry.html#pointFloatAttribValuesAsString [www.sidefx.com]
Technical Discussion » H17.5 packed disk performance: hours-long mantra init time
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- jpparkeramnh
- 178 posts
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Technical Discussion » xform from external file
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- jpparkeramnh
- 178 posts
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If you want a Houdini way to extract the matrix, you can try using the “Extract Transform” OBJ node, as long as the topology is the same between the objects.
Solaris » ggx bsdf function
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- jpparkeramnh
- 178 posts
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Great to know that CVEX BSDF code will still be supported in Karma. Sometimes just being able to hack something shot specific into a BSDF via VEX is more valuable than absolute performance.
That said, will there be a public API to create custom C++ BSDFs?
That said, will there be a public API to create custom C++ BSDFs?
Technical Discussion » How Hscript and Expressions are different?
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- jpparkeramnh
- 178 posts
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Ah when I say shell, I mean how you would type in a Linux (or Mac) command line terminal.
Technical Discussion » How Hscript and Expressions are different?
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- jpparkeramnh
- 178 posts
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I “rediscovered” Hscript a little bit recently when using it to run Houdini in terminal mode instead of Hython. As a shell-like experience I find it nicer than using Python as the syntax is cleaner and easier to type, for example when listing the contents of a network and rendering:
Python:
Hscript:
Python:
o = hou.node('/out') print o.children() o.node('mantra1').render()
Hscript:
cd /out ls render mantra1
Technical Discussion » H17.5 packed disk performance: hours-long mantra init time
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- jpparkeramnh
- 178 posts
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I've not had to do this in the past yet, so I might be missing something easy…
So I have a scene with a particle simulation that repeats along the edges. It has 9 million points. I'm creating about 3000 packed copies of it in a tiling pattern. When the points are just points (spheres) I can render it quickly and with low memory.
So now I want to replace each point with a packed disk prim, with a total variety of about 100 packed disk items. And when I do that, I wait hours before even seeing the first bucket.
So take a step back, and I render just one simulation copy with the packed disks instanced to each point, and the render time of that is reasonable.
Is there a way to make the full nested setup work quickly?
So I have a scene with a particle simulation that repeats along the edges. It has 9 million points. I'm creating about 3000 packed copies of it in a tiling pattern. When the points are just points (spheres) I can render it quickly and with low memory.
So now I want to replace each point with a packed disk prim, with a total variety of about 100 packed disk items. And when I do that, I wait hours before even seeing the first bucket.
So take a step back, and I render just one simulation copy with the packed disks instanced to each point, and the render time of that is reasonable.
Is there a way to make the full nested setup work quickly?
Technical Discussion » VEX point cloud masterclass / tips?
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- jpparkeramnh
- 178 posts
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Thanks all, appreciate the reply. There's no free lunch here… and no substitute for a lack of free time to play around with the functions myself.
Technical Discussion » VEX point cloud masterclass / tips?
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- jpparkeramnh
- 178 posts
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tamte
I think Jon means functions like pcopenlod() and pcsampleleaf() which can speed up point cloud queries
https://www.sidefx.com/docs/houdini/vex/functions/pcopenlod.html [www.sidefx.com]
https://www.sidefx.com/docs/houdini/vex/functions/pcsampleleaf.html [www.sidefx.com]
I have seen them being used in the shading context, however never used them myself
Yes, exactly… Jeff Wagner talks about pgfind in his VEX masterclass and touches on point clouds a little bit, but sometimes it's hard to creatively imagine novel uses for these. I'm guessing a lot of them were added with specific use cases in mind.
Some sort of example page with snippets for each would be fun to create some day. (Matt Estela?
)
Technical Discussion » VEX point cloud masterclass / tips?
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- jpparkeramnh
- 178 posts
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srletak76
Only thing that you need to know about Houdini it's this
Than just combine
https://www.youtube.com/watch?v=dq5B3TeFeL8 [www.youtube.com]
Sorry but I didn't see anything about the point cloud specific VEX function that I mentioned. I'm not a beginner by any stretch of that word.
Technical Discussion » VEX point cloud masterclass / tips?
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- jpparkeramnh
- 178 posts
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Often, for common point lookup tasks, for the sake of ease, when I want to look up point info I just use the nearpoint() function or just a simple pcopen() followed by pcfilter(). I've also used pciterate and the other related functions for occasional purposes.
But there are a lot of point cloud functions I never use, and because they exist, they must be useful. Ideally I'd want to find out which ones will make my point lookups as fast as possible.
Are there any pro-level tutorials that go over them with examples anywhere?
Cheers,
Jon
But there are a lot of point cloud functions I never use, and because they exist, they must be useful. Ideally I'd want to find out which ones will make my point lookups as fast as possible.
Are there any pro-level tutorials that go over them with examples anywhere?
Cheers,
Jon
Technical Discussion » Houdini 6.5 questions :)
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- jpparkeramnh
- 178 posts
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Houdini Lounge » Karma roadmap
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- jpparkeramnh
- 178 posts
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rmagee
We have just posted a comparison of Karma and Mantra in the FAQ section to show you where all the features stand at the moment:
https://www.sidefx.com/faq/karma/ [www.sidefx.com]
This is great, thanks!
Houdini Lounge » Future of Mantra
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- jpparkeramnh
- 178 posts
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MidphaseBrianHanke
Renderman seems nice, but it has some seriously janky elements compared to Mantra
What don't you like about Renderman?
Since they took away SL, a lot of constraints were added that are still possible in VEX. Here are a couple more:
- No closure support in OSL, so mixing BSDFs is a pain. Try mixing multiple volume phase functions in RenderMan…
- Looking up arbitrary geometry attributes is also a pain (primuv, pcfind, etc.).
- Not being able to create lens shaders with a shading language.
Technical Discussion » Houdini Packages
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- jpparkeramnh
- 178 posts
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I've written some pipeline tools that do a lot of things that the Houdini package format is supposed to do, but for any software environment one would want to configure. As long as the necessary Houdini environment variables are being automated in some other way, is there any reason to switch?
Technical Discussion » Karma procedural shading — Bugs, Quirks, Feedback
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- jpparkeramnh
- 178 posts
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jsmackThat just makes me sad. There are plenty of real production use cases where one would want to send out rays to probe the scene that don't fall into the BSDF domain.
It's expected that dirt/occlusion masks don't work with Karma. trace/gather are not allowed in Karma.
Even OSL still supports trace() functions.
Technical Discussion » Houdini 18 Karma Custom Fisheye Lens Shader Revisited
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- jpparkeramnh
- 178 posts
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Jeroen,
I just missed entering the beta and we would have expected the same capability at AMNH. Probably like you, we use mantra because of its extreme flexibility that other renderers (I'm looking at you Pixar!) have eschewed over recent years, but are a necessity to do special format rendering of non-standard topics, for example rendering super computer simulations that are structured unlike typical VFX assets… ie, spherical volumes, massive particle counts, etc.
Having not been able to explore Karma and LOPs yet I'm hoping we can push our tools forward to take advantage of it,as long as the flexibility in rendering is still there.
Cheers,
Jon
I just missed entering the beta and we would have expected the same capability at AMNH. Probably like you, we use mantra because of its extreme flexibility that other renderers (I'm looking at you Pixar!) have eschewed over recent years, but are a necessity to do special format rendering of non-standard topics, for example rendering super computer simulations that are structured unlike typical VFX assets… ie, spherical volumes, massive particle counts, etc.
Having not been able to explore Karma and LOPs yet I'm hoping we can push our tools forward to take advantage of it,as long as the flexibility in rendering is still there.
Cheers,
Jon
Technical Discussion » CHOPS frame offset
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- jpparkeramnh
- 178 posts
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The “lookup” CHOP will do that and fancier things too, or you can use a CHOP expression in the Shift node to look up the first sampled frame index.
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