You can do it with VEX. See the “timefilter” node and take a look at the vex function, within the for loop. You could reproduce the functionality within a VOP COP.
I'm not sure how fast it is to do it this way, though it would probably be faster than doing it in a python COP.
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Technical Discussion » Compositing - Max value over time
- jparker
- 289 posts
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Houdini Lounge » WIP python script: Isolate Tool
- jparker
- 289 posts
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Instead of using /tmp for your object information you could also store it on the Python hou.session module. Just assign like thus:
hou.session.isolateNodePaths =
This information isn't saved with the scene, but if you wanted it to persist you could use hou.appendSessionModuleSource:
http://www.sidefx.com/docs/houdini12.5/hom/independent [sidefx.com]
http://www.sidefx.com/docs/houdini12.5/hom/hou/appendSessionModuleSource [sidefx.com]
hou.session.isolateNodePaths =
This information isn't saved with the scene, but if you wanted it to persist you could use hou.appendSessionModuleSource:
http://www.sidefx.com/docs/houdini12.5/hom/independent [sidefx.com]
http://www.sidefx.com/docs/houdini12.5/hom/hou/appendSessionModuleSource [sidefx.com]
Houdini Lounge » easy way to repeat uv in houdini
- jparker
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The simplest answer is that to get a texture to repeat you need to divide s and t by 1 or 2, not multiply .
There is also a UVTransform VOP for more advanced controls.
To control multiple shaders / textures at once the easiest way is to create parameter VOPs for your texture repeat multipliers and wire them into each node you want to control. You now have access to your parameters at the material level where you could set multiple shaders at once.
There is also a UVTransform VOP for more advanced controls.
To control multiple shaders / textures at once the easiest way is to create parameter VOPs for your texture repeat multipliers and wire them into each node you want to control. You now have access to your parameters at the material level where you could set multiple shaders at once.
Houdini Lounge » Expressions, best practice
- jparker
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For expressions that need to work quickly for multiple prims/points/vertices there are also the new *Wrangle SOPs, which are meant to replace some of the functionality of the Point/Primitive SOPs. There are new “point”, “prim” and “detail” VEX functions that can be used like the hscript equivalent.
From what I understand hscript would be very hard to multithread so it's speed will become more limited as time goes on and performance increases come by way of more CPU cores rather than speeding up single CPU speeds.
From what I understand hscript would be very hard to multithread so it's speed will become more limited as time goes on and performance increases come by way of more CPU cores rather than speeding up single CPU speeds.
Technical Discussion » note on memory usage when rendering lots of particles
- jparker
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Points as particle systems actually render as spheres by default, whereas without the particle primitive they are simply points. That's my guess as to why they took so much more memory.
-Jon
-Jon
The Orbolt Smart 3D Asset Store » custom bsdfs (and other reseach-oriented assets)
- jparker
- 289 posts
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Greetings,
Something super-useful that I think would really gravitate many of us to orbolt for would be assets that are really heavy on the maths implementation side… the perfect example being CVEX bsdf implementations derived from cutting edge research. Implementing MIS algorithms takes a lot of time and testing (for me at least), and in small VFX shops many of us definitely don't have the time to go through the R&D required to get everything right. I think people would be willing to pay money for this, even.
Just a thought.
-Jon
Something super-useful that I think would really gravitate many of us to orbolt for would be assets that are really heavy on the maths implementation side… the perfect example being CVEX bsdf implementations derived from cutting edge research. Implementing MIS algorithms takes a lot of time and testing (for me at least), and in small VFX shops many of us definitely don't have the time to go through the R&D required to get everything right. I think people would be willing to pay money for this, even.
Just a thought.
-Jon
Houdini Lounge » Houdini 13 Wishlist.
- jparker
- 289 posts
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I don't know if it's been mentioned already (probably has): update the IFD file format (and Mantra… and Houdini) to support nested procedurals!
Houdini Lounge » ABSOLUTELY AWESOME !!!!!
- jparker
- 289 posts
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Houdini Lounge » OpenVDB
- jparker
- 289 posts
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Easily might be a relative term, as I've never made a procedural using the HDK. Worth looking into, though, although by the time it takes me to get it written, compiled and usable, Side Effects will likely have already integrated it…
Houdini Lounge » OpenVDB
- jparker
- 289 posts
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Houdini Lounge » Nebulae and Galaxies
- jparker
- 289 posts
- Online
I helped generate the background nebulae for Eve Crucible (mmpog):
http://www.youtube.com/watch?v=uXFuMyuWFDU [youtube.com]
These were done with volume primitives and lots of shader work in Houdini 10. There is some detailing from matte painting but the images are 95% from Houdini. The render times were long but there were a lot of things that could have been optimized.
I'll paraphrase some advice I gave elsewhere:
When shading nebulae it's important to note that they are typically one of three types, or mixture of them:
Emission nebula - these are transparent but emit light through ionization.
Absorption nebula - what it sounds like, dark nebula that block light. Some nebulae will have an emission front ahead of the edges of the molecular dust that absorbs the light. The key to this effect is to make sure your volume opacity is colored, towards a reddish / brownish tint (or the compliment), in order for it to redden objects behind it (note: colored opacity seems to be broken using stochastic transparency in H12).
Reflection nebula - reflect light from nearby stars. These can normally be treated like regular fog, although they really behave more like the atmosphere of the earth, where Raleigh scattering makes them appear blue-ish. Usually no shadowing is needed for these.
Mix these together in one scene to get space telescope style images.
You can create a volume primitive for emission and another for absorption, and just pipe them into your shader as parameters of the same name. The emission volume would receive but not cast shadows, and the absorption volume would be dark and a shadow caster. For a typical Hubble-esque image you can shrink the absorption volume slightly to create the halo effect. For reflection nebulae you can treat them much like standard smoke or dust.
HTH,
jon
http://www.youtube.com/watch?v=uXFuMyuWFDU [youtube.com]
These were done with volume primitives and lots of shader work in Houdini 10. There is some detailing from matte painting but the images are 95% from Houdini. The render times were long but there were a lot of things that could have been optimized.
I'll paraphrase some advice I gave elsewhere:
When shading nebulae it's important to note that they are typically one of three types, or mixture of them:
Emission nebula - these are transparent but emit light through ionization.
Absorption nebula - what it sounds like, dark nebula that block light. Some nebulae will have an emission front ahead of the edges of the molecular dust that absorbs the light. The key to this effect is to make sure your volume opacity is colored, towards a reddish / brownish tint (or the compliment), in order for it to redden objects behind it (note: colored opacity seems to be broken using stochastic transparency in H12).
Reflection nebula - reflect light from nearby stars. These can normally be treated like regular fog, although they really behave more like the atmosphere of the earth, where Raleigh scattering makes them appear blue-ish. Usually no shadowing is needed for these.
Mix these together in one scene to get space telescope style images.
You can create a volume primitive for emission and another for absorption, and just pipe them into your shader as parameters of the same name. The emission volume would receive but not cast shadows, and the absorption volume would be dark and a shadow caster. For a typical Hubble-esque image you can shrink the absorption volume slightly to create the halo effect. For reflection nebulae you can treat them much like standard smoke or dust.
HTH,
jon
Houdini Lounge » Do we really need Nuke or After Effects ?
- jparker
- 289 posts
- Online
COPS is an indispensable part of Houdini, especially for image processing that is meant to feed your other networks, and in fact I wish Side Effects would turn their attention to it a bit more and spruce a few things up so I could use it more often to finish off renders.
That said, there is no way it can replace Nuke, and you will never find that happening in a studio. Nuke is just too good at what it does.
That said, there is no way it can replace Nuke, and you will never find that happening in a studio. Nuke is just too good at what it does.
Houdini Lounge » What gpu to choose actualy?
- jparker
- 289 posts
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I have a Quadro 4000 with 2GB of VRAM, and I ran a brief test with OpenCL and was only able to sim up to about 220^3 voxels, which is not enough to really show off the GPU's power. So I agree, RAM is really important for simulation on the GPU.
Technical Discussion » pyro2 noise volume vop context
- jparker
- 289 posts
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Ah great, thanks for the patch.
FWIW I think it's great that you can use these outside of a SHOP context. I do a lot of volume density manipulation testing in COPs because it's a lot faster and easier to test things out there first before I commit to large render times. So these new nodes will really come in handy!
-Jon
FWIW I think it's great that you can use these outside of a SHOP context. I do a lot of volume density manipulation testing in COPs because it's a lot faster and easier to test things out there first before I commit to large render times. So these new nodes will really come in handy!
-Jon
Technical Discussion » pyro2 noise volume vop context
- jparker
- 289 posts
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I'm getting two errors when I try to use the unified noise VOP in a volume VOP context:
call to undefined function float_pyro_vopfw_VOP_CTXT()
invalid type on right side of assignment: undefined
Do the pyro nodes not work in this context? In my view this is an area where the new noise functions in particular would be most useful.
-Jon
call to undefined function float_pyro_vopfw_VOP_CTXT()
invalid type on right side of assignment: undefined
Do the pyro nodes not work in this context? In my view this is an area where the new noise functions in particular would be most useful.
-Jon
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