Nick Petit

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obj-image Houdini HIVE
New RBD Workflow Tools in Houdini 18

Recent Forum Posts

RBD Guided simulation removal Feb. 14, 2024, 6:37 p.m.

The "Evaluation Node Path" parameter defines the node from which to evaluate
ch(), chs(), etc
VEX commands on (the parm search path). The default, set to "." means it'll evaluate parms on the RBD Bullet Solver SOP node directly, so adding a "detachframe" attribute on the RBD Bullet Solver node directly can be referenced with
float detachframe = ch("detachframe");
for example.

Most VEX functions take a geometry as first argument, so, in your case, you can specify it as "op:<path to node>", i.e:
int npts = npoints("op:/obj/geo1/refgeo");

Collision shape in RBD Bullet Solver only shows Convex Hull? Jan. 19, 2024, 7:58 p.m.

On the RBD Bullet Solver, "RBDs" or "Geometry" refers to the geometry plugged into the 1st or 3rd inputs. "Collision" refers to the geometry plugged into the 4th input.

That is correct, the Geometry Representation menu in the Collisions tab refers to the collision geo plugged into input 4.

The visualization tab has options for both the Geometry/RBDs (plugged in 1st or 3rd inputs) and the Collision (plugged in 4th input)

Displaying the Visualization > Geometry > Collision Shape shows the collision shape for the RBD geo.
Displaying the Visualization > Collision Geometry > Collision Shape shows the collision shape for the Collision geo.

This visualization geo is extracted directly from DOPs. If you aren't seeing what you expect, it'll be because you aren't setting the geo representation as you think.

The settings on the RBD Bullet Solver SOP are all overridden by attributes set on the input geo, either set manually or via a RBD Config SOP.

You cannot change the Geometry/RBD collision shape (geometry representation) on the RBD Bullet Solver node itself, you need to change it by setting the "bullet_georep" string point attribute on the packed fragments. The RBD Config SOP has options for setting this.

Here's an example file with 3 different setups. The default (everything comes in as convex hulls), the RBD Bullet Solver's Collision Geometry Representation changed to Sphere, and finally overrides using the RBD Config SOP.

Although the RBD Bullet Solver's UI has changed significantly since 18.5, the parms and the way this works hasn't changed, so you should see the same results (despite some warnings when you open the file).

Collision shape in RBD Bullet Solver only shows Convex Hull? Jan. 19, 2024, 4:21 a.m.

The RBD Bullet Solver's Collision tab is to control the collision geo plugged into the 4th input.
The RBDs (plugged into the 1st and/or 3rd input) come in as Convex Hulls by default. To change that, use a RBD Configure SOP to change the bullet_georep.