Okay, so It makes a bit more sense now (thanks mitch!). The note at the top of the state pop docs says it all, “Most POPs will not process particles with non-zero states, as it would, for example, be inefficient to process dead particles. ”.
So in my particular case, once the particle had stopped, it's state was non-zero and therefore the velocity was not being updated. Adding a velocity pop with an expression if($STUCK,0,$VX) seemed to work around it in my case.
Still don't know why the bounce on collision with values of 0 for gain on normal and tangent causes the particle to fall through the floor, but I suppose you could argue why I would want to do that anyway.
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Technical Discussion » pops - weird velocity, what's the backtrack attrib?
- pinkwerks
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Technical Discussion » pops - weird velocity, what's the backtrack attrib?
- pinkwerks
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I've been trying to scale some faked rotation on particles using the magnitude of the velocity. The problem is velocity never reaches zero when the particle comes to a rest. Why a particle at rest has a velocity greater than zero is beyond me - I must be missing something about the way houdini solves it's particle update (vs. maya).
Anyway, I've noticed that my pop net produces a ‘backtrack’ variable, a float vector with 4 components that looks suspiciously like the kind of data I'm after (and expect to some degree). What's odd, is this attribute isn't documented anywhere that I can find - any knowledge about this out there? It appears to correspond to velocity, but properly zeros out when the particle comes to rest. What's the 4th component of this all about?
(edit: looks like the 4th component is something like timestep/FPS)
The second part to this confusion is why when I set particles to bounce on collision, with a Normal and Tangent Gain of zero, my particle insists on falling through the ground plane - after a very brief pause due to collision.
Anyway, I've noticed that my pop net produces a ‘backtrack’ variable, a float vector with 4 components that looks suspiciously like the kind of data I'm after (and expect to some degree). What's odd, is this attribute isn't documented anywhere that I can find - any knowledge about this out there? It appears to correspond to velocity, but properly zeros out when the particle comes to rest. What's the 4th component of this all about?
(edit: looks like the 4th component is something like timestep/FPS)
The second part to this confusion is why when I set particles to bounce on collision, with a Normal and Tangent Gain of zero, my particle insists on falling through the ground plane - after a very brief pause due to collision.
Houdini Indie and Apprentice » Tracing an image
- pinkwerks
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Like so? This is using foreach. Also, from the poly extrude help page:
“For example you can use fit01(rand($PR), 0.2, 0.6) in the Translate Z field to create random extrusion heights for each input polygon face.”
“For example you can use fit01(rand($PR), 0.2, 0.6) in the Translate Z field to create random extrusion heights for each input polygon face.”
Technical Discussion » Group performance and the name attribute
- pinkwerks
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While diagnosing why a hand made RBD fractured network with bullet was running much slower than shelf made one, it was discovered that the culprit was in how you made your groups.
It seems when specifying the pieces you can either have it look at groups using ‘Group Mask’ with something like “piece*”, or as the shelf does, ‘Fracture by name’. Both work, but the ‘Fracture by name’ works much faster.
After a little discussion I heard some lore about ‘groups being slow’, and I was hoping someone could speak to this? Are groups as name attributes the way forward? Is it better to create groups on the fly using the at sign ‘@’ syntax than to pass them from sop to sop where possible? Is this a dop only issue?
thanks for any comments. this is in h12.581
It seems when specifying the pieces you can either have it look at groups using ‘Group Mask’ with something like “piece*”, or as the shelf does, ‘Fracture by name’. Both work, but the ‘Fracture by name’ works much faster.
After a little discussion I heard some lore about ‘groups being slow’, and I was hoping someone could speak to this? Are groups as name attributes the way forward? Is it better to create groups on the fly using the at sign ‘@’ syntax than to pass them from sop to sop where possible? Is this a dop only issue?
thanks for any comments. this is in h12.581
Technical Discussion » New Site Install
- pinkwerks
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Houdini will run just fine from a network disk. However, with windows you'll need to install the vcredistributable packages on those machines (which is part of the windows installer), which kind of defeats the purpose of having a network copy - so you don't have to install to all the machines.
However once you've done this, you can update to a dot-release and just run Houdini from the network location and avoid a mass install.
Be warned, we found that in previous versions, the permissions weren't locked down on the installs, and allowed non-admin users to inadvertently modify the contents of the hfs directory - which is pretty a much a no no IMHO. They have supposedly fixed this in the new 12.x releases, though I haven't personally verified this.
It would be nice if you could just shove the vcredist stuff in the houdini directory so you could just roll out one copy, but I think that would require some work on sidefx's part - RFE maybe…
However once you've done this, you can update to a dot-release and just run Houdini from the network location and avoid a mass install.
Be warned, we found that in previous versions, the permissions weren't locked down on the installs, and allowed non-admin users to inadvertently modify the contents of the hfs directory - which is pretty a much a no no IMHO. They have supposedly fixed this in the new 12.x releases, though I haven't personally verified this.
It would be nice if you could just shove the vcredist stuff in the houdini directory so you could just roll out one copy, but I think that would require some work on sidefx's part - RFE maybe…
Houdini Indie and Apprentice » Velocity Blur versus Rendered Motion Blur?
- pinkwerks
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The nature of a 2d blur vectors is always linear. You'll never get curved motion - at least not with current techniques. The vector can only describe a direction and magnitude. If you want curved blur you'll have to render it.
The good news is mantra is decent fast at this. Play with the motion factor and xform time samples.
The good news is mantra is decent fast at this. Play with the motion factor and xform time samples.
Houdini Indie and Apprentice » Nurbs nornals
- pinkwerks
- 49 posts
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Hi this is a me too. I'm gettting strange results with nurbs and normals.
Attached is a file that shows this. Walking through the provided examples, you can see how some of nurbs show a primitive normal - some don't. Also, the direction of the line sop seems to change the behavior of when a primitive normal shows up.
Attached is a file that shows this. Walking through the provided examples, you can see how some of nurbs show a primitive normal - some don't. Also, the direction of the line sop seems to change the behavior of when a primitive normal shows up.
Houdini Indie and Apprentice » Use of op: with pcopen in a shop context?
- pinkwerks
- 49 posts
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I figured it was something like that, but after playing around all day the brain was stretched and I couldn't think it through properly. Thanks!
Houdini Indie and Apprentice » Use of op: with pcopen in a shop context?
- pinkwerks
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Just when I think I'm out of the woods… So I changed the shop to use a pc file. However, I notice I'm getting some sort of phantom point appearing in my render. Even if I scatter zero points, the pcfilter is causing a weird artifact in the center of the shader result. Maybe I'm accessing some invalid data?
In general is it okay to use pcfilter, or is iterating over the pcopen better practice? pcfilter is so much easier, so I hope that's not the case.
In general is it okay to use pcfilter, or is iterating over the pcopen better practice? pcfilter is so much easier, so I hope that's not the case.
Houdini Indie and Apprentice » Use of op: with pcopen in a shop context?
- pinkwerks
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Houdini Indie and Apprentice » Use of op: with pcopen in a shop context?
- pinkwerks
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So I have a basic, color the surface according to nearby points from a point cloud setup.
I'm able to use a pcopen and pcfilter vop with the op: syntax for the point cloud texture file to color points in a sop context. The result isn't smooth enough for me so I want to get the coloring done at render time. However, If I use the same vop network in a mantra shader I can't get any results. I believe I've taken care to transform P, and I'm using the full path in op expression.
I'd like to avoid writing out a PC file to disk, though, I'm not sure if this is possible.
I'm able to use a pcopen and pcfilter vop with the op: syntax for the point cloud texture file to color points in a sop context. The result isn't smooth enough for me so I want to get the coloring done at render time. However, If I use the same vop network in a mantra shader I can't get any results. I believe I've taken care to transform P, and I'm using the full path in op expression.
I'd like to avoid writing out a PC file to disk, though, I'm not sure if this is possible.
Technical Discussion » custom attributes with point instances
- pinkwerks
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Okay, so I managed to do what I was after from my previous post. Attached is a file that accomplishes reading a different disk bgeo for each of my instance points.
This should let you playback different frames of pre-cached animation for different points. The real work is initializing the custom ‘cache_frame’ attribute in the attached example to control what point gets what frame. You'll need to cook out /obj/write_geo for this example to work.
More or less it boiled down to not worrying about setting up material overrides and more about just using instancepoint() in the delayed load procedural to look up a point attribute. I guess I was over complicating it.
An improvement would be to figure out how to get the correct bounding box inserted dynamically into delayed load procedural for the given frame. Currently the example hard-codes it. Suggestions welcome.
This should let you playback different frames of pre-cached animation for different points. The real work is initializing the custom ‘cache_frame’ attribute in the attached example to control what point gets what frame. You'll need to cook out /obj/write_geo for this example to work.
More or less it boiled down to not worrying about setting up material overrides and more about just using instancepoint() in the delayed load procedural to look up a point attribute. I guess I was over complicating it.
An improvement would be to figure out how to get the correct bounding box inserted dynamically into delayed load procedural for the given frame. Currently the example hard-codes it. Suggestions welcome.
Technical Discussion » custom attributes with point instances
- pinkwerks
- 49 posts
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Use delayed load procedural to load the geometry for the instance. Then you override the parameter that specifies what files to use.
I'm trying to do this - basically I have a series of bgeo on disk. I would like every point that is instanced to read a different frame from that series. So I made a delayed load shader and assigned it to my instance. Now, on the material tab of the instance I've tried to create local material parameters from the menu - in hopes that I could override the string used to look up the file name per instance. However, I get this error : “Warning: /shop/vm_geo_file1 is not a material”, when trying to ‘Create All Local Material Parameters’.
I'm confused on how to add a string override for the file parameter of the delayed load shader as you suggest.
Technical Discussion » Float Type images planes not showing up in .exr
- pinkwerks
- 49 posts
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The quick solution is to promote them to vectors. Many compositing packages don't know how to handle arbitrary single channels that aren't part of layers. Even though the exist in the EXR - You can investigate this by using ‘exrheader’.
Nuke for instance sees the channels but to get at them, you need to use a copy node, but you should see them available as other.whatever in your mask operations for instance.
Nuke for instance sees the channels but to get at them, you need to use a copy node, but you should see them available as other.whatever in your mask operations for instance.
Houdini Lounge » Hair Shader's Specular still broken?
- pinkwerks
- 49 posts
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I haven't used houdini in a couple years, and I can't believe I'm being bit by this bug tonight, two years later.
I've tried disconnecting the hair normal and ‘shade as curves’ but I'm still getting nothing :?
–edit–
I was able to work around this by replacing the hairSpec with a regular specular node.
I've tried disconnecting the hair normal and ‘shade as curves’ but I'm still getting nothing :?
–edit–
I was able to work around this by replacing the hairSpec with a regular specular node.
Houdini Indie and Apprentice » ODE example?
- pinkwerks
- 49 posts
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Great thanks - this is what I was looking for. I had a feeling about it not supporting the fractured object sop - but couldn't express how i needed a copy sop like solution - which the RBD point object sop does beautifully.
Nice move setting the normals for rotation too! This should be an example file.
Nice move setting the normals for rotation too! This should be an example file.
Houdini Indie and Apprentice » ODE example?
- pinkwerks
- 49 posts
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I can't seem to make the simplest Open Dynamics Engine rigid body dynamics simulation work. (sorry so verbose, the forum sucks for searching 3 letter words) It's basically a cube copied to some grids. Then i want them to drop and hit the ground colliding with each other along the way. No biggie.
Except for my simulation explodes or doesn't do anything. I have a feeling I'm not configuring my ODE object for the simulation correctly.
These were my steps more or less - After creating a the /obj/cubes. Make a rbd ground plane with the shelf. Click on the /obj/cubes and make a rbd fractured object. In the auto dop network append a ‘ode configure object’ after the ‘rbd fractured object’ and change the rbd solver to ODE. Not much happens like i think it should at this point.
Could someone look at this a enlighten me?
Except for my simulation explodes or doesn't do anything. I have a feeling I'm not configuring my ODE object for the simulation correctly.
These were my steps more or less - After creating a the /obj/cubes. Make a rbd ground plane with the shelf. Click on the /obj/cubes and make a rbd fractured object. In the auto dop network append a ‘ode configure object’ after the ‘rbd fractured object’ and change the rbd solver to ODE. Not much happens like i think it should at this point.
Could someone look at this a enlighten me?
Technical Discussion » efficient fur rendering
- pinkwerks
- 49 posts
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I've gotten some excellent results from houdini using the micropolygon renderer at HD. Full screen characters (squirrels) with motion blur rendering around 40 minutes a frame. I don't use anything but distant lights with depth map shadows (with transparency). An environment light for a base color (if you have HDR) can be used for ambiance too.
A good hack is to use the ambient occlusion sop with your skin (floating around in the exchange) and use the resulting attribute in the hair shader to transfer the AO shadowing to the hair color.
Also, for motion blur we've been getting away with geometry velocity blur.
A good hack is to use the ambient occlusion sop with your skin (floating around in the exchange) and use the resulting attribute in the hair shader to transfer the AO shadowing to the hair color.
Also, for motion blur we've been getting away with geometry velocity blur.
Houdini Lounge » Diagnosing errors
- pinkwerks
- 49 posts
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I find diagnosing errors in houdini to be a bit difficult. My latest frustration came when renders would simply complain and cause houdini to exit with a status of 1 - screwing up my render scripts:
Skipping unrecognized parameter “folder1”.
Not a very informative message. Turns out, I had an otl in my home directory, but not on the render machine - fair enough but it took a week to figure out what node was causing it. My real question or complaint is - why doesn't it offer a better message with the actual path to the object? :
Skipping unrecognized parameter “/obj/foo/myotlnode/folder1”.
I find this same kind of behavior when trying to figure out which one of my materials is missing a texture map. For instance:
Unable to access file foo.pic
Unable to load texture ‘foo.pic’
Again - WHICH NODE is the problem? Is it a light, or material, a vop? This seems unnecessarily hard. I even turned the mantra verbosity to max, however it offers no clues. How do others deal with this - am I missing something?
Skipping unrecognized parameter “folder1”.
Not a very informative message. Turns out, I had an otl in my home directory, but not on the render machine - fair enough but it took a week to figure out what node was causing it. My real question or complaint is - why doesn't it offer a better message with the actual path to the object? :
Skipping unrecognized parameter “/obj/foo/myotlnode/folder1”.
I find this same kind of behavior when trying to figure out which one of my materials is missing a texture map. For instance:
Unable to access file foo.pic
Unable to load texture ‘foo.pic’
Again - WHICH NODE is the problem? Is it a light, or material, a vop? This seems unnecessarily hard. I even turned the mantra verbosity to max, however it offers no clues. How do others deal with this - am I missing something?
Technical Discussion » SPH stickability
- pinkwerks
- 49 posts
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This has been brought up before - it seems to still be an outstanding problem.
http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&p=71245&sid=fcb3a42c4ce96329ea2c0dbc97a94217 [sidefx.com]
Maybe submitting an RFE?
http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&p=71245&sid=fcb3a42c4ce96329ea2c0dbc97a94217 [sidefx.com]
Maybe submitting an RFE?
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