Multiple skeletons for single entity with multiple meshes?

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The thing is that the bounding boxes are used by the picking engine for a fast check against a mesh, but if the ray does intersect the box after this check, the engine goes further and looks for an actual intersection with the geometry.

The problem with skeleton animated meshes is that the geometry is the initial geometry, none of the transformations applied by the animation are reflected into the geometry because the computations are done in a vertex shader and so are not visible from the javascript code. So, the geometry intersection test is done against the untransformed geometry, that’s why it does not work as expected.

What I have just said is true if the bone computations are done in the vertex shader, which is the default. However, you can instruct the engine to perform those computations on the CPU (mesh.computeBonesUsingShaders = false), in which case everything will work as expected because the actual geometry data are really updated according to the animation:

https://playground.babylonjs.com/#YA8851#9

Two important things to make this work:

  • you should call mesh.refreshBoundingInfo() with a false parameter (or no parameter at all) and not with true, else you will apply two times the deformation from the skeleton, as the geometry data are already transformed by the animation!
  • you should call makeGeometryUnique on your cloned meshes, else they will all share the same geometry and so they will all be animated with the same animation

Of course, doing it this way is less performant than doing it on the CPU…

One possibility if you still want to use GPU computation is that we add a flag on the picking method so that it stops when the bounding box intersection is ok and does not go to the geometry intersection checking stage. The check won’t be pixel perfect but it could be enough in your case. I will make a PR for this as it is really easy (it’s already taken care in the computation but this flag is not visible from the user side).

Note that for both cases above to work, you should refresh the bounding info each frame as the methods rely on those boxes being right. It’s not so much a problem in the first case as the geometry data on the CPU side is already transformed by the animation, so it’s only a matter of scanning those data to extract the min/max vectors. However, in the second case, you will need to call refreshBoundingInfo(true) which will apply the skeleton transformation to the geometry data before the scan, in effect cancelling the benefit of doing the computations on the GPU… So, your option here would be to pre-compute the bounding boxes for each frame of each animation and simply sets the right bounding box depending on the current frame of the anim (the first case would also benefit from this, of course).

You have another option which is to use GPU picking. It’s more involved, you can look for more information in this forum, for eg: Speeding up scene.pick() on renderloop

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