Monthly Archives: March 2014

Triangulation Bug ?

While working on the next video tutorial I appear to have found a bug.  The drop sheets over primitives and figures are clearly okay, but when I re-created a conforming costume this caused the plugin to crash unexpectedly.

I was able to narrow the problem down to the costume mesh.  The mesh must be triangulated before converting it into a conforming costume.  The previous example with the Long Green Dress was triangulated but the new test costume was not.

The 0.0498 release version of the plugin removes the quads / triangle mode but this problem is more likely related to how the facet mesh moves through the modifier stack.  The real cause is as yet unclear.  The fix is to make sure to manually triangulate the mesh.

Cloth Tutorials

After the public release of the latest code for the Cloth Deformer I wanted to revise the results I posted last year and re-create them with some video tutorials.

A drop sheet is always the most basic test to run – if that fails to work then the simulator is worthless.  So for the second tutorial I wanted to drop a bed sheet over a moving figure and then I decided to try and push the simulator and keep the figure moving under the sheet for at least 10 seconds.

It took a several draft simulations to get it right.  There were a few problems when the hands moved into the sheet and then proceeded to push through it – so I had to adjust the animation to avoid this problem and keep the hands out of the way.  Since the simulation result is not known until it has run, getting a hand to interact with the cloth part the way through is just too complex.

Something to keep in mind with cloth simulation is that in reality you can be constrained by clothing and cloth.  Tight non-stretch pants won’t allow you to run easily and when you’ve been double wrapped up all cosy in a bed sheet and quilt it is hard to suddenly spring out of bed without kicking and fighting your way out.

I also used different settings from the tutorial video.  I needed to set much higher friction and dampening values – otherwise the sheet slid off the figure and half the way off the bed by the end of the simulation to leave her exposed.  Also in the tutorial video some kooky key frames had got in and turned her elbows into bent straws.  I didn’t notice that until it was too late and uploaded, so hopefully the focus is all on the cloth.

Each simulation took at least 4 hours to run.  I spent at least 4 hours on key framing the animation (which isn’t that great) and the rendering took almost 4 hours as well – so running the simulation (while I slept) wasn’t really that big an issue in the production time.

Cloth Tutorial 2 Results

The twitching in the animation was much lower than I expected but I’m still more personally interested in the potential of the still frame results with my plugin.

What really worked surprisingly well was when she turns over to one side and also how the legs moved under the sheet.

A final note was that I might have made the animation physics even more interesting by using the Jiggle Deformer but alas it is not currently compatible with the Cloth Deformer.  The trouble is that Jiggle will not produce the same results when it is run at 150 fps as when it is run at 25 fps.  I will have to add a new recording mode into JIggle to use it with Cloth.  This would need to allow the results to be saved and played back without recalculation.