RBD Fracture has a Group Mask option to limit which groups are used for creating new pieces. The value in this file is *, which means each group creates its own piece. Unfortunately, the group SOP is creating the group “group1” with all of the primitives in it. Thus, the RBD fracture creates one object that is the entire statue and lots of small pieces. Since these all overlap, they get stuck together from their surface points and you get a slow sim that can't shatter.
If you open Details View while looking at the DOP network you can see the extra “group1” object.
The simplest and most robust solution is to look at the Assemble SOP. You will note it has an Output Prefix which defaults to “piece”. This means the groups it creates are called piece1, piece2, etc. In the RBD Fracture DOP, set the Group Mask to “piece*”. It will then only use those groups for creating the pieces.
The shelf tool for RBD Glue Object should be setting the Group Mask to piece*, but isn't. A bug has been submitted for that deficiency.
- Jeff
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Houdini Indie and Apprentice » First Post -Shatter Object?
- jlait
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Houdini Lounge » Vorticle force
- jlait
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The gas vorticle geometry only uses the expression at the first frame. Thus, it doesn't update over time. This node is designed to just initialize the vorticles.
Technical Discussion » Ripple DOP
- jlait
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To avoid the reflected wave you can paint a lower dissipation along the boundary. In 9.1 and later the dissipation has been renamed to the more correct “conservation”. Earlier in this thread is an example file of using dissipation to dampen the boundary conditions.
Setting a dissipation/conservation to 0.95 or similar across the entire grid will likewise cause the waves to fade out.
- Jeff
Setting a dissipation/conservation to 0.95 or similar across the entire grid will likewise cause the waves to fade out.
- Jeff
Technical Discussion » [HCS] Dark Houdini Color Scheme
- jlait
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I believe you have to edit the opcreation script to set the opcolor to something else. Worse yet, a lot of digital assets have their own colours hardcoded.
Best I can suggest is $HH/scripts/opmacros/createnode
Best I can suggest is $HH/scripts/opmacros/createnode
Technical Discussion » [HCS] Dark Houdini Color Scheme
- jlait
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We've added a .hcs section to the Exchange for people to publish their favorite colour schemes.
Please name them other than UILight.hcs, however, as future versions of Houdini will be able to handle different named colour schemes.
Please name them other than UILight.hcs, however, as future versions of Houdini will be able to handle different named colour schemes.
Technical Discussion » Ripple DOP
- jlait
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Deforming the rest without the rest springs is unintuitive.
What is happening is that the wave shape used for the calculations is the difference between the surface and the rest object. By changing the rest surface, you change the surface seen by the solver. For example, if you push down the rest surface, the solver will see a bump at that location. When it flattens that bump the result is a dimple in the original surface (as it is operating independently of the rest surface).
The more intuitive approach is to directly manipulate the water surface. I couldn't give that as an option in the object, however, as that would then rewrite the object surface every frame removing the effect of the waves.
There is another, entirely unrelated to Rippling water, reason why you'd want to deform the rest surface. This solver can be used as a jiggle type solver on actual geometry. The rest surface can be the animating character. If springs are added, you get the main surface moving to the rest surface. The wave motion will then be propagated along the object by the solver, in a more softbodyish manner.
- Jeff
What is happening is that the wave shape used for the calculations is the difference between the surface and the rest object. By changing the rest surface, you change the surface seen by the solver. For example, if you push down the rest surface, the solver will see a bump at that location. When it flattens that bump the result is a dimple in the original surface (as it is operating independently of the rest surface).
The more intuitive approach is to directly manipulate the water surface. I couldn't give that as an option in the object, however, as that would then rewrite the object surface every frame removing the effect of the waves.
There is another, entirely unrelated to Rippling water, reason why you'd want to deform the rest surface. This solver can be used as a jiggle type solver on actual geometry. The rest surface can be the animating character. If springs are added, you get the main surface moving to the rest surface. The wave motion will then be propagated along the object by the solver, in a more softbodyish manner.
- Jeff
Technical Discussion » angvel through Dops
- jlait
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It uses the velocity (v) attribute to compute both the linear and the angular velocity.
If your source has angular velocity, each point on it will be pointing in a different direction. These differences can be used to figure out what spin is present.
If your source has angular velocity, each point on it will be pointing in a different direction. These differences can be used to figure out what spin is present.
Technical Discussion » Ripple DOP
- jlait
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The best answer I've got to the open end conditions is to paint a region of dissipation around the boundary. The attached example shows this in action.
There is still reflections occurring whenever the dissipation steps up, but by spreading the reflection over several points on the grid they will cancel each other out and the wave will disappear.
There is still reflections occurring whenever the dissipation steps up, but by spreading the reflection over several points on the grid they will cancel each other out and the wave will disappear.
Technical Discussion » Ripple DOP
- jlait
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Deforming rest works. The Rest SOP Path needs to point to /obj/grid_object1/rest1 and the Initial SOP to /obj/grid_object/grid1. This is opposite to your attached file. If I reverse those and turn on deforming rest, it works.
Note that changing the rest geometry creates a sort of fluid potential rather than an actual fluid motion. Another approach to collisions is to use the Ray SOP to displace the actual grid geometry inside a SOP solver. Attached is such an example.
Note that changing the rest geometry creates a sort of fluid potential rather than an actual fluid motion. Another approach to collisions is to use the Ray SOP to displace the actual grid geometry inside a SOP solver. Attached is such an example.
Technical Discussion » Flowfields
- jlait
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Wave was what Ripple was briefly called. So there is no wave, just ripple. To the distress of mathematicians, “Wave” makes people think of breaking waves, which are difficult to have in a pure 2d world.
Technical Discussion » Non Volume-Based Collision Detection for Particle Fluids
- jlait
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Detecting blocks hitting the outside is what the Force Bounds option helps avoid.
I think a solution to the hanging-blocks problem was added in 9.0.754. However, it does not take effect by default nor is it available as an option in SIM_SDF.
On the IsoOffset SOP there are some otions to control “sign sweeps” that try and clean up those big blocks of bad geometry.
I think a solution to the hanging-blocks problem was added in 9.0.754. However, it does not take effect by default nor is it available as an option in SIM_SDF.
On the IsoOffset SOP there are some otions to control “sign sweeps” that try and clean up those big blocks of bad geometry.
Technical Discussion » "Volume attributes" and fluid fields
- jlait
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Such a visualization would be very useful. There is no current built-in way of doing that, sadly. The closest would be to use the HDK to write your own visualization using the GR_RenderHooks, but that is not for the faint of heart.
RFE: 28340
- Jeff
RFE: 28340
- Jeff
Technical Discussion » "Volume attributes" and fluid fields
- jlait
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Yes, you just have to objectmerge or dopimport the velocity field and merge it with the density field. vel.x, vel.y, and vel.z will be bundled up in the vector vel which Mantra recognizes for velocity fields.
Note you do not have to use Smoke Visualization. Instead of specifying smoke/vel/Visualization, directly specify smoke/vel. This will bring in the field as a volume primitive regardless of visualization settings. This is useful as you likely are playing around with visualization when testing the sim and don't want to worry about setting it back to smoke for the actual real sim.
Note you do not have to use Smoke Visualization. Instead of specifying smoke/vel/Visualization, directly specify smoke/vel. This will bring in the field as a volume primitive regardless of visualization settings. This is useful as you likely are playing around with visualization when testing the sim and don't want to worry about setting it back to smoke for the actual real sim.
Technical Discussion » "Volume attributes" and fluid fields
- jlait
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The way to do this now is by object merging your desired fields into the object to render. Instead of having one volume primitive with several attributes (say, density, temperature) you have one volume primitive per attribute. The name primitive attribute marks the role of each of your volume primitives. By default, the primitives exported from DOPs will have appropriate names attached to them.
Then, in mantra, you merrily add a “temperature” parameter to your shader. This will be overridden on a per sample basis with the incoming temperature field.
This is, for example, how the per voxel motion blur picks up the velocity attribute from simulations.
Then, in mantra, you merrily add a “temperature” parameter to your shader. This will be overridden on a per sample basis with the incoming temperature field.
This is, for example, how the per voxel motion blur picks up the velocity attribute from simulations.
Technical Discussion » Custom vorticles
- jlait
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I'm glad you figured out the transformation issue.
I'm not sure what you mean by “Smoke doesn't trailing vorticles”, however?
Are the vorticles not following the smoke?
I'm not sure what you mean by “Smoke doesn't trailing vorticles”, however?
Are the vorticles not following the smoke?
Technical Discussion » Combining RBD with SOP Solver forces SDF-calc on each frame
- jlait
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Under the Collisions::Volume tab of the RBD Object you can set a file to save the .sdf to. Set the operation to Automatic will write out the file when you first cook it and then use that file for future frames rather than recooking.
Technical Discussion » RBD weight problem
- jlait
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Hello.
The problem is that you only have a one-way constraint set up. The weight is being forced onto the beam, but nothing is forcing the beam back to the weight. To set up a two-way, or pin, constraint, you need to add a second constraint on the beam object pointing back to the weight.
At the same time, it would be good to reset the weights mass to avoid serious instability.
Attached is a version which hopefully works for you.
The problem is that you only have a one-way constraint set up. The weight is being forced onto the beam, but nothing is forcing the beam back to the weight. To set up a two-way, or pin, constraint, you need to add a second constraint on the beam object pointing back to the weight.
At the same time, it would be good to reset the weights mass to avoid serious instability.
Attached is a version which hopefully works for you.
Technical Discussion » BUG : popshapematch parameters do nothing
- jlait
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The strength of those values is clamped to your frame rate. Any higher a value will result in an unstable system that blows up immediately.
The non-linear nature is because they act as scales.
The non-linear nature is because they act as scales.
Technical Discussion » Strange houdini behaviour in linux
- jlait
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This is likely a tablet initialization error.
You can likely remove the error by setting HOUDINI_ENABLE_LINUX_TABLET to 0. You should still be able to use the tablet as a mouse device, it is just support for pressure sensitivity in the Paint SOPs that will be lost.
Houdini expects the tablet to be installed as “stylus”, “eraser”, and “cursor”, which should match the installation instructions here:
http://linuxwacom.sourceforge.net/index.php/howto/all [linuxwacom.sourceforge.net]
You can likely remove the error by setting HOUDINI_ENABLE_LINUX_TABLET to 0. You should still be able to use the tablet as a mouse device, it is just support for pressure sensitivity in the Paint SOPs that will be lost.
Houdini expects the tablet to be installed as “stylus”, “eraser”, and “cursor”, which should match the installation instructions here:
http://linuxwacom.sourceforge.net/index.php/howto/all [linuxwacom.sourceforge.net]
Technical Discussion » L-system long variables problem?
- jlait
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I'm sorry for the confusion. LSystem expression variables can only be one character long. The LSystem expression parser is very character driven and has this as a rather deep built in assumption. (There is an internal array 256 entries long to store all the variable values, for example)
I think you got the reference to 5 where it says there can be up to 5 userdefined variables. This is no longer the case now that we have multiparms to define user variables, you can now have considerably more. You are still limitted by the built in definitions of:
a, b, c, d, g, i, t, x, y, z, A, L, T, U, V, W.
- Jeff
I think you got the reference to 5 where it says there can be up to 5 userdefined variables. This is no longer the case now that we have multiparms to define user variables, you can now have considerably more. You are still limitted by the built in definitions of:
a, b, c, d, g, i, t, x, y, z, A, L, T, U, V, W.
- Jeff
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