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Technical Discussion » Smoke Solver without source volume
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- Skybar
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He is sourcing from the SOP Vector Field DOP called “get_color”. In the sim he only got this color field and velocity, so the “smoke” you are referring to is the color field visualized as smoke (Vector Field Visualization node).
Technical Discussion » use packed rbd sim as "static deforming objects"
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- Skybar
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First, you cant use the Static Solver for this. You need to use the bullet solver. Then either set active,animated,deforming attributes correctly (you still have those from the previous sim, which is set wrong for the new sim). Or delete those attributes and set the initial object type to “create animated static objects”. Yes you should use animated static in this case, since they are animated and not deforming. Animated is usually a lot faster as well so you should do that whenever you can.
Technical Discussion » Looping Smoke with gasresizefluiddynamic
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- Skybar
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Copy the resizing simulation into a static sized volume. Then you can do the loop on that.
Technical Discussion » How extract camera rotation as world-space rotation?
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- Skybar
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You can use vtorigin() for translations and vrorigin() for rotations.
http://www.sidefx.com/docs/houdini/expressions/vtorigin.html [www.sidefx.com]
http://www.sidefx.com/docs/houdini/expressions/vrorigin.html [www.sidefx.com]
http://www.sidefx.com/docs/houdini/expressions/vtorigin.html [www.sidefx.com]
http://www.sidefx.com/docs/houdini/expressions/vrorigin.html [www.sidefx.com]
Houdini Lounge » wrangle ? what does it mean?
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“to argue or dispute, especially in a noisy or angry manner.”
This makes sense sometimes too.
http://www.dictionary.com/browse/wrangle [www.dictionary.com]
This makes sense sometimes too.
http://www.dictionary.com/browse/wrangle [www.dictionary.com]
Technical Discussion » Smoke solver - adding voxels
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- Skybar
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fuosNo idea about that, but I meant sparse as in terms of VDBs. Compression might be possible though? Dont knowSkybar
You cannot do it in DOPs though afaik.
Oh I was under the impression that losseless compression happens on contiguous areas. Poor looking lossy compression can happen with the Tolerance value on Scalar/VectorFields. VDB should just also have very fast access to voxels as well as being sparse.

Technical Discussion » Smoke solver - adding voxels
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- Skybar
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I think this is using VDB (sparse), take a look at that: http://www.orbolt.com/asset/953u6015t::pyrojunior
You cannot do it in DOPs though afaik.
You cannot do it in DOPs though afaik.
Houdini Lounge » splitting and recombining paths in vex.
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- Skybar
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Why do you want the expression in the attribute at all? Why not evaluate it in the wrangle, and make the attribute look like dir/folder/imageseq.4.exr.
Technical Discussion » volumesample filtering
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- Skybar
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Doesn't seem to have changed since 9.5 at least.
http://www.sidefx.com/docs/houdini9.5/vex/functions/volumesample [www.sidefx.com]
http://www.sidefx.com/docs/houdini9.5/vex/functions/volumesample [www.sidefx.com]
Technical Discussion » problem with emitting RBD objects using POPs
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- Skybar
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You can do it like this. Setup everything (name, active) before the sim, just use one RBD Packed Object DOP and then just emit All Geometry with Pop Source.
Edited by Skybar - 2018年2月20日 08:32:53
Houdini Lounge » Performance difference between AttributeVOP SOP and Wrangle SOP?
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- Skybar
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It's probably faster for people that know and like to write code. Otherwise VOPs is just fine for the rest of us.
Technical Discussion » Shrinking large Vdb files
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- Skybar
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Deactivate the vel field using density as a mask. That way you only get velocity where you need it for rendering.
Technical Discussion » How to have GI emission have an effect on volumetrics
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- Skybar
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It's probably because emission is indirect light (?), so raising volume limit above 0 makes sense. If you want direct light I guess geometry light is the way to go.
Technical Discussion » $PI in @variable...
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- Skybar
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You can access it as a vex variable if you do:
#include <math.h>
@test = PI;
@test2 = PI_2;
@test3 = PI_4;
So in your example you could replace $PI/2 with PI_2, if you include math.h at the top.
#include <math.h>
@test = PI;
@test2 = PI_2;
@test3 = PI_4;
So in your example you could replace $PI/2 with PI_2, if you include math.h at the top.
Houdini Lounge » Some Threadripper results
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- Skybar
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Houdini Lounge » Huge bugbear: why does Houdini default to start at frame 1, not zero?
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Technical Discussion » Portal interior lighting and noise
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- Skybar
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You can do that in mantra too, there are checkboxes for image planes of direct/indirect ray samples.
Technical Discussion » Portal interior lighting and noise
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- Skybar
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EnivobUhm, no? Minimum is the starting point everywhere, so even if an area only “need” 1 ray it will use the minimum. Then based on the threshold it will increase sampling to get rid of noise until either a) the maximum rays is reached or b) you've hit the noise threshold, whichever comes first. If the threshold is set too low it will probably always use the maximum amount of rays all the time, so it takes some fine-tuning depending on the case.
The threshold acts like a switch, not a meter AFAIK. So below the threshold you get MIN samples and above or equal you get MAX samples. When you specify 1 for min and 20 for max you are actually saying use 1 or 20 samples, not 1 to 20 samples. By moving the numbers closer together you can even the spread so to speak. Then you are saying use 4 or 16 samples. That is just my preference, one sample is never enough. You need at least 2-3 minimum.
Houdini Lounge » Houdini 16 - Flip Fluid Upresing ?
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- Skybar
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I have one question. The thing I'm working on needs to be pretty quick, so I upped the initial velocity to 10, both for the boundary vel and initial vel on the flipobject. However, doing this the top of the river starts eating itself forward and I get a gap where it won't seed any particles (because the surface isn't there anymore?). Eventually the velocities at the top there goes really crazy and kinda blows up in a big wave.
In the boundary_layer_river.hip, set your initial velocities to 30 or higher and you'll see what I mean.
Why does this happen? Is it a case of needing substeps or something else?
edit: It works a lot better if I add a source to fill in that gap, and the velocities there no longer blows up as well. But this seems a bit counter-intuitive seeing as the setup is “source-less”. Could the problem be because the particles is being seeded and then advected directly afterwards? As opposed to sourcing post-solve which seems to “solve” it.
In the boundary_layer_river.hip, set your initial velocities to 30 or higher and you'll see what I mean.
Why does this happen? Is it a case of needing substeps or something else?
edit: It works a lot better if I add a source to fill in that gap, and the velocities there no longer blows up as well. But this seems a bit counter-intuitive seeing as the setup is “source-less”. Could the problem be because the particles is being seeded and then advected directly afterwards? As opposed to sourcing post-solve which seems to “solve” it.
Edited by Skybar - 2017年3月2日 11:36:45
Houdini Lounge » Houdini 16 - Flip Fluid Upresing ?
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