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#Renderman vs mental ray how to#

a strut constraint for internal strength.

a pressure constraint to keep the mesh inflated a bit.

a cloth constraint to pin to the animated feet and animated head.

Knowing that vellum happily supports multiple constraints doing different things, this has: Watched a few Entagma and Sidefx vids, saw a fun walking setup on Twitter, had a go myself. To work out the breaking threshold I just hit a single tree with the sphere, gradually increasing the threshold until it looked like it snapped at the right time. By swapping the mode from 'permanent' to 'soft', the strength can be controlled and breakable can be enabled. To control stiffness and breaking, I removed the pins, made a new vellum constraints node, mode 'pin to target', and gave it the root group from before.īy default this is a permanent pin, which has almost no controls. When done this way the pins will inherit the same stiffness values as the rest of the hair. In the first stage I pinned using the existing vellum configure hair node. Probably worth pointing out what the second vellum configure node is for.

#Renderman vs mental ray how to#

The hip does more stuff (colliders, breakable pin constraints, plasticity, scale to a forest etc), but recognizing wireframe things need hair constraints rather than cloth, and how to identify when the number of constraint iterations are too low, were the important lessons here. can disable collisions to speed things up a little, don't need them for now.Can play with the ratio of substeps to constraint iterations, remember 1 substeps with 100 constraint iterations is roughly the same as 2 substeps at 50 iterations, but will solve more accurately (and be a little slower). Set substeps to 2, sim again, the tree is stable. On the lsystem increase the generations from 7 to 8, which grows an extra set of twigs.

Lets see what we can do to push this a bit and learn some more. Dive inside the solver, connect a popwind before the force output null, wind strength 0.1 on x, noise amplitude 0.25.Jump to the solver, set constraint iterations from 100 to 1000, sim.Next aha moment: If you do powers-of-ten jumps in stiffness but don't see any change the higher you go, the constraint iterations are too low!.on vellum configure hair, the bend stiffness is too low.on vellum configure hair, set pin points to group1.insert a group sop after the lsystem, set group type to 'points', base group 0, ie, the first point.append a solver, watch it fall to its doom.This was my first aha moment: when simulating wire/skeletal things, use vellum configure hair, not cloth! I got a better feel for vellum after watching the John Lynch masterclass a few times, taking notes (see below). It'd flop about, fall apart, no matter what I tried. 18 John Lynch Advanced Vellum workflowsĭownload hip: File:vellum_forest_lsystems.hipĪ thing I found surprisingly tricky was to take the default lsystem tree and convert it to vellum.10 Vellum jelly with embedded rigid object.