Hi, I have a simple particle integrator for quick RBD pre-visualisation. I wanted to match what I would get from a bullet SIM with no collisions (basically just the initial forces, and gravity) but Rotational Stiffness is modifying the initial angular momentum of the bullet sim, causing the output of my integrator to be different (since Rotational Stiffness is defaulted to 1).
Can someone help me add a rotational stiffness/inertial tensor stiffness calculation to my integrator in VEX?
Thanks!
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Technical Discussion » Applying inertial tensor stiffness to my simple integrator
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- JordanWalsh
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Technical Discussion » Creating an HDA that Instantiates Multiple Nodes at Once
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- JordanWalsh
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Technical Discussion » Houdini render volume with depth
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- JordanWalsh
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Zdepth makes no sense for semi transparent renders.. you will need to render out a deep camera map pass.
https://www.sidefx.com/docs/houdini/render/dcm.html [www.sidefx.com]
https://www.sidefx.com/docs/houdini/render/dcm.html [www.sidefx.com]
Technical Discussion » Packed Disk Sequence Questions
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- JordanWalsh
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So im building my own code to handle subframes and the index. All is going well but seems the python code errors:
returning this error:
Using setattrib in Vex is a workaround, but seems like this is a bug in python?
prim.setIntrinsicValue("filenames", files) // where files is a tuple of string filenamesreturning this error:
return _hou.Prim_setIntrinsicValue(*args) OperationFailed: The attempted operation failed. Invalid number of elements for this intrinsic
Using setattrib in Vex is a workaround, but seems like this is a bug in python?
Technical Discussion » Packed Disk Sequence Questions
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- JordanWalsh
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So how does PDS deal with subframe caches on disk?
Think of a bat that beats its wings about 17 times a second. I would want to cache the file in 1/8 frame increments. Can PDS deal with this? At the moment it only seems to want to pull in the $F file name, not any of the subframes saved using $FF in the file name.
Think of a bat that beats its wings about 17 times a second. I would want to cache the file in 1/8 frame increments. Can PDS deal with this? At the moment it only seems to want to pull in the $F file name, not any of the subframes saved using $FF in the file name.
Technical Discussion » Generate velocity from volume
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- JordanWalsh
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You cant generate a vel from just the fog volume, it makes no sense. You will need the original particles with a v attrib already calculated then just add the v attribute on the VDB From Particles node, or use a volume velocity node to create the vel from your points.
Technical Discussion » Alembic and packed objects question
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- JordanWalsh
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Not sure about Maya, but its usually a good idea to use a path attribute to partition your geo. If you pack i think that is what takes care of the partitioning… added bonus, if you are using packed to do instancing, either packed disk or packed geo and you are saving to a single file the alembic will try to use alembic instancing where it writes the single instances to file once then just adds transforms for the frame range. I have had files go from 5Gigs down to 400 mb (where im instancing a lot).
I would try to use poly soups for most things. Ive heard that with only a few polys soups can be more inefficient.
I would try to use poly soups for most things. Ive heard that with only a few polys soups can be more inefficient.
Technical Discussion » where is the "adata input" in H15 in "Add Attribute node ?"
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- JordanWalsh
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Than node only adds an attribute and its defaults/local variables, use a bind node or a setattrib node to actually set the value
Technical Discussion » Volume VOP & noise
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- JordanWalsh
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You could also have a noiseAmp attribute on the points or your line then use a point cloud open + point cloud filter to read in the attribute then wire that into the amplitude of your noise
Technical Discussion » Changing FPS in FLIP
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- JordanWalsh
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Ok, so I was wrong, it not a bug, its actually that the Increase Range should only be set to a value from 0-1. Setting it to 3 broke the maths (as it uses a power function that needs a 0-1 to be correct). Doing what I said above will give you very different results.
What you want to change is your Output Range to add more temperature, so set that to 0-3 and put the Increase Rate back to something more useful, like 0.9
What you want to change is your Output Range to add more temperature, so set that to 0-3 and put the Increase Rate back to something more useful, like 0.9
Technical Discussion » Changing FPS in FLIP
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- JordanWalsh
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Ok, looks like there is a bug in the heatingvolume1 node. If you allow editing, go into the popvop1 and look at the mulconst1 node, it is hard coded to multiply the timeInc by 24… change it to 50 and it works when you are at 50fps.
By the way DONT change the Timescale when you change the FPS. time scale is based on seconds, not frames, so you dont need to update this. If you look onyour AutoDop at the Time Step you will notice it update correctly when you change the FPS
By the way DONT change the Timescale when you change the FPS. time scale is based on seconds, not frames, so you dont need to update this. If you look onyour AutoDop at the Time Step you will notice it update correctly when you change the FPS
Technical Discussion » Changing FPS in FLIP
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- JordanWalsh
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Well if you are messing with the FPS and want everything to stay the same you need to avoid using anything referencing frames, like $F, $SF, @Frame etc and you need to use @T, @ST for referencing time instead. That way your expressions will stay the same no matter what the FPS is.
I'd start by looking and converting all these over before you adjust your FPS. but other than that I think Houdini should be pretty robust when changing FPS… not that i have tried!!!
I'd start by looking and converting all these over before you adjust your FPS. but other than that I think Houdini should be pretty robust when changing FPS… not that i have tried!!!
Technical Discussion » Varying Instanced Geometry
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- JordanWalsh
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ahhh, yeah, sorry about that 
Will not show up in the viewport as the original brick is sitting in memory and being streamed to the video card, so it cant be modified on the way and stay nice and instanced
Will not show up in the viewport as the original brick is sitting in memory and being streamed to the video card, so it cant be modified on the way and stay nice and instanced
Technical Discussion » Varying Instanced Geometry
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- JordanWalsh
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If you have Cd on the packed prim object then you need to pud down a renderState Node and add in packed:Cd in the value name. Set the signiture to vector and you should be good to go.
Other wise the just using a Parameter/Bind will try to get the attribute off the unpacked geo when rendering.
The mantra shader in 15 should do this exactly
edit:
works perfectly on the attached file:
Other wise the just using a Parameter/Bind will try to get the attribute off the unpacked geo when rendering.
The mantra shader in 15 should do this exactly
edit:
works perfectly on the attached file:
Technical Discussion » Baking animation to key per frame
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- JordanWalsh
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Hey Pete,
I tried it using a null with (set to python language):
hou.node(“/obj/null_leaf/”).worldTransform().extractTranslates()
hou.node(“/obj/null_leaf/”).worldTransform().extractTranslates()
hou.node(“/obj/null_leaf/”).worldTransform().extractTranslates()
in the translates to get the world pos of the leaf node, but couldnt get the bake to do anything either
I tried it using a null with (set to python language):
hou.node(“/obj/null_leaf/”).worldTransform().extractTranslates()
hou.node(“/obj/null_leaf/”).worldTransform().extractTranslates()
hou.node(“/obj/null_leaf/”).worldTransform().extractTranslates()
in the translates to get the world pos of the leaf node, but couldnt get the bake to do anything either
Technical Discussion » Motion blur on Pyro Smoke
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- JordanWalsh
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Technical Discussion » Motion blur on Pyro Smoke
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- JordanWalsh
- 144 posts
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It is taking the vel field and using that to add motion blur. I think you will find if you do a volume trail on your vel field you would have those massive velocities in the middle.
The error come into it because your vel field is a representation of the instantaneous velocity of the system, not how the smoke is moving over the shutter time.
Best bet is to clamp the magnitude of the vel filed.
eg:
in a volume wrangle to clamp to 10:
@vel=normalize(@vel)*clamp(length(@vel), 0, 10);
The error come into it because your vel field is a representation of the instantaneous velocity of the system, not how the smoke is moving over the shutter time.
Best bet is to clamp the magnitude of the vel filed.
eg:
in a volume wrangle to clamp to 10:
@vel=normalize(@vel)*clamp(length(@vel), 0, 10);
Technical Discussion » Creating multiple dop objects from copy/stamp
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- JordanWalsh
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Hi,
Im trying to create multiple DOP objects from a source of points that have some geo copy stamped to the points with some upstream stamping to vary the shapes.
Im using the solid solver and have almost recreated a copy stamp setup.
The issues I am having are that I cant seem to get the SOP Geo DOP to do any stamping outside the dop network, it seems I have to tuen off “Use External SOP”.
Also Im having trouble matching up my embedded geo for the solid solver (which is actually the real reason I want to do it this way).
Any thoughts?
Thanks!
Im trying to create multiple DOP objects from a source of points that have some geo copy stamped to the points with some upstream stamping to vary the shapes.
Im using the solid solver and have almost recreated a copy stamp setup.
The issues I am having are that I cant seem to get the SOP Geo DOP to do any stamping outside the dop network, it seems I have to tuen off “Use External SOP”.
Also Im having trouble matching up my embedded geo for the solid solver (which is actually the real reason I want to do it this way).
Any thoughts?
Thanks!
Technical Discussion » How to inject velocity into my explosion
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- JordanWalsh
- 144 posts
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Just had a quick look at your file.
Input 1 is for setup, honestly you dont need to touch it unless you need more fields for processing if you are doing some tricky effects.
You should be able to get everything you want from sourcing density temp and volume into the 4th input.
Use the shelf tools and see how they are setup.
Have a look at my example in the second dop network. Using this setup and probable some motion blur on the source, or custom streaking on the fast particles
Input 1 is for setup, honestly you dont need to touch it unless you need more fields for processing if you are doing some tricky effects.
You should be able to get everything you want from sourcing density temp and volume into the 4th input.
Use the shelf tools and see how they are setup.
Have a look at my example in the second dop network. Using this setup and probable some motion blur on the source, or custom streaking on the fast particles
Technical Discussion » How to inject velocity into my explosion
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- JordanWalsh
- 144 posts
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Dops isnt the same as sops. It dosent flow from top to bottom, so can be confusing. Im just attaching data to a force that gets evaluated by the solver.
Maybe have a read of this: http://www.tokeru.com/cgwiki/index.php?title=HoudiniDops [tokeru.com]
Some helpful stuff in there
Maybe have a read of this: http://www.tokeru.com/cgwiki/index.php?title=HoudiniDops [tokeru.com]
Some helpful stuff in there
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