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Technical Discussion » constraints for packed prims
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- cwhite
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Just a note - either the ‘name’ or ‘dop_object/name’ syntax can be used, but prefixing with the DOP object name is a good idea - this is what the shelf tools try to do, as it avoids any ambiguity if there are multiple RBD Packed Objects where packed primitives have the same names (and can save you a lot of debugging later on)
Technical Discussion » constraints for packed prims
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- cwhite
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Technical Discussion » Deleting glue constraints as part of a RBD simulation.
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- cwhite
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In this case the Overwrite with SOP parameter shouldn't be used, since it will completely overwrite the constraint network's geometry each frame (which will restore any constraints that were broken by the solver).
I think the simplest approach is run a SOP solver over the constraint network's geometry to remove any primitives that no longer exist in your animated constraint network (if you set up a primitive attribute with a unique id for each constraint, then this can be determined easily with the findattribval VEX function).
I think the simplest approach is run a SOP solver over the constraint network's geometry to remove any primitives that no longer exist in your animated constraint network (if you set up a primitive attribute with a unique id for each constraint, then this can be determined easily with the findattribval VEX function).
Technical Discussion » Bullet and voronoi clustering
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- cwhite
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I'm not quite sure if I understand your question, but (since Houdini 12.5, I think) the Bullet solver attempts to prevent initially interpenetrating objects from immediately being pushed apart.
Technical Discussion » Bullet Collision geometry slowness
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- cwhite
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Ah, that makes sense. It's much more efficient to use the ‘name’ attribute to partition the primitives instead of having a separate primitive group for each piece.
Technical Discussion » Bullet Collision geometry slowness
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- cwhite
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That sounds very slow for only 11000 objects - it would be a good idea to submit a bug
Technical Discussion » How do I avoid rebuilding viewport geometry per-frame?
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- cwhite
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I think http://www.sidefx.com/docs/hdk14.0/_h_d_k__geometry__intro.html#HDK_Geometry_Intro_Data_IDs [sidefx.com] should cover what you're looking for.
Technical Discussion » Attrib wrangle tips?
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- cwhite
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If you don't want to create attributes, just do:
vector min, max;
getbbox(min, max);
vector center = (min+max)/2;
v@v = (@P - center) * ch('mult');
vector min, max;
getbbox(min, max);
vector center = (min+max)/2;
v@v = (@P - center) * ch('mult');
Technical Discussion » Glue Constraint Issues
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- cwhite
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josh_hakim
I am currently working through a houdini destruction tutorial and the glue constraints one hold when there is one object in the scene. Once two objects are in the scene together, the glue constraint fails.
Josh
The points on your constraint network reference objects with names such as ‘piece0’, but that's ambiguous since there are multiple packed primitives in your scene which have that name.
In Houdini 14, constraint networks allow you to optionally prefix the packed primitive name with the DOP Object name (e.g. ‘Roof_Side/piece0’) to fix the ambiguity - shelf tools such as RBD Glue Object will set this up automatically. Otherwise, you can adjust the name prefix on the Voronoi Fracture SOP (or the Assemble SOP, depending on where your name attribute is being generated in your setup) to be unique.
Technical Discussion » Constraints Getting Stuck
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- cwhite
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I don't recall fixing any bugs with cone twist constraints since the H14 release, so please file a bug report (https://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=15603) [sidefx.com] if you think there is an issue.
Houdini Indie and Apprentice » Connect Adjacent Pieces minimum radius?
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- cwhite
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There's nothing built in, so I'd suggest submitting an RFE for this.
It's fairly straightforward to do in VEX using the pcfind function, though (or in VOPs with the Point Cloud Find node) - the Connect Adjacent Pieces SOP is just a digital asset, so you can take a look inside at what it does when the Connection Type parameter is set to Adjacent Points.
It's fairly straightforward to do in VEX using the pcfind function, though (or in VOPs with the Point Cloud Find node) - the Connect Adjacent Pieces SOP is just a digital asset, so you can take a look inside at what it does when the Connection Type parameter is set to Adjacent Points.
Technical Discussion » Constraints Getting Stuck
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- cwhite
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The expression is for the ‘Overwrite with SOP’ parameter on the Constraint Network SOP. If you're opening an old file with a more recent build of H14, you can just revert that parameter to its default expression.
Technical Discussion » ConeTwist Constraint Setup, H13 - H14
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- cwhite
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I'm not sure why editing the Connect Adjacent Pieces SOP is necessary - I think the “Adjacent Pieces from Points” mode does what you're looking for?
Technical Discussion » adjacent pieces coming back after impact.
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- cwhite
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It sounds like you might be hitting the same issue as https://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=37732. [sidefx.com] If resetting that parameter's expression to the default doesn't fix your issue, then I'd suggest posting a file and/or sending it to support.
Houdini Lounge » Questions about Houdini Bullet
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- cwhite
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Also note that in H14 you can use the ‘collisionignore’ point attribute to filter collisions against specific DOP objects, or against groups of packed primitives based on the ‘collisiongroup’ attribute (these are documented under the Collision Attributes section of https://www.sidefx.com/docs/houdini14.0/nodes/dop/rbdpackedobject) [sidefx.com]
Technical Discussion » Houdini 14 Glue Network changes
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- cwhite
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Houdini Learning Materials » RBD Glue Object is overly attached to itself?
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- cwhite
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You probably need to update to a more recent build of H14:
Friday, January 16, 2015
Houdini 14.0.216: Fixed a bug in the default expression for the Overwrite with SOP parameter on Constraint Network DOP, which caused the constraint network geometry to be re-imported after the first frame even if it wasn't time dependent.
Technical Discussion » Issues with Bullet in H14
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- cwhite
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The behaviour you're seeing appears to have been caused by a change made in 14.0.207:
I've reverted that change in tomorrow's build, since it caused some stability issues in certain situations (such as your attached file) that are more severe than the original bug.
Houdini 14.0.207: Fixed a bug in the Bullet library where angular momentum was not correctly conserved. This sometimes caused objects to exhibit unexpected behavior, such as a tall and thin object being unable to topple over.
I've reverted that change in tomorrow's build, since it caused some stability issues in certain situations (such as your attached file) that are more severe than the original bug.
Technical Discussion » H14 Bullet generating too much impact data
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- cwhite
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That memory usage sounds suspiciously high - I'd suggest sending a bug report with that file to support.
Turning off “Add Impact Data” will prevent the Bullet solver from recording anything to the “Impacts” subdata on the DOP object - that can reduce the memory usage somewhat if there are many impacts and you don't have any need for that data.
Turning off “Add Impact Data” will prevent the Bullet solver from recording anything to the “Impacts” subdata on the DOP object - that can reduce the memory usage somewhat if there are many impacts and you don't have any need for that data.
Technical Discussion » RBD Initial State /w Packed Primitives
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- cwhite
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Currently, the initial pivot needs to be set to a sensible value (e.g. P) - that's what happens behind the scenes in the RBD Point Object. There's an active RFE to improve this behaviour, though, and make it simpler to correctly set up initial angular velocities.
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