edward lam


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Bone Capture Regions and Biharmonics Aug. 19, 2018, 3:12 p.m.

From what I can tell, the Bone Capture Lines SOP for biharmonic bone capturing doesn't use most of the capture region information that exists. I can change the capture region cap sizes all I want and it doesn't effect the biharmonic solution. Changing the height of the regions will, but only if I have “Use Bone Link” turned off. Additionally, as far as I've been able to tell, changing the capture region cap sizes doesn't change anything in the resulting geometry spreadsheet of the Bone Capture Biharmonic SOP or the Bone Capture Lines SOP.

For historic reasons, Houdini started with only the Bone Capture method which used the capture regions for weighting AND deforming. In this method, the points are weighted using distances of the point within a bone's region. Then the complete state of the capture pose, the capture region transforms and its shape values are stored into the geometry itself by the Bone Capture SOP. Then at animation time, the Bone Deform SOP takes the deform region transforms and its cap values to deform the geometry (relative to the information stored within). You get no deformation when both sets of transform/cap values match. When they differ, then the deform region information is used to deform the skin relative to the capture region information.

Then when we added the Bone Capture Proxity SOP method. In this case, the shape of the capture region doesn't get used for computing weights since the purpose of the method is to use spatial distance to weight the points from the center line segment of the capture regions. However, it still records the capture region transforms and cap values into the geometry. So if you change the deform region information, it still deforms as in the original Bone Capture method. The Bone Deform SOP does not behave any differently nor know which weighting method was used.

Similarly, for the bone Bone Capture Biharmonic SOP method. For this, weights are computed over a tetrahedral mesh using the mesh edges for distances. Again, the Bone Deform SOP is orthogonal to this. The capture region is baked into geometry and deformation occurs identically as in the original Bone Capture method.

I hope this explains the current behaviour in Houdini 16.5. For the next upcoming major release, we've basically removed using the region cap values for deformation. Old scene files will still load and deform the same way but newly created setups will use the newly rewritten Bone Deform SOP that sports a simplified parameter interface. Deforming using the region cap values were using a very inefficient code path that was not multithreaded and produced questionable quality results. Another problem with using the cap values is that round-tripping out to FBX and back was impossible since FBX (nor any of the other DCC packages, game engines) supported this deformation method.

Sidefx Houdini and Newtek Lightwave Support? Feb. 26, 2018, 11:32 a.m.

Houdini crash on startup (Graphics Driver conflict) Feb. 21, 2018, 11:26 p.m.

We recently figured that crashlogs like the above indicate a conflict with sound drivers that use the Nahimic audio engine. If you've got anything audio installed like MSI Realtek, MSI Nahimic, ASUS Sound Studio, then this is likely the culprit. We've found that upgrading them to the latest in the some cases fixes the problem.