I'm back with my leg/knee simulation. I am very mcuh enjoying my time with Ziva.
The progress video is posted:
Last weekend I marathon modeled all the muscles that come in and out of the knee (and aductors) and almost have the leg "shape" complete. This weekend I watched Andy's webinar replays and went back to simming. I created a line of action for the calf muscle heads. I did some conceptual cheating with attachments at the knee joint to try to preserve the visual silhouette of what I am visualizing someday driving the skin. Some volumes disappear into the femur, but I am going with this as a trick to try to get the fold right. The quad is really attached to the femur and patella in order to coax it into working. I started with some careful attachment painting for the muscles below the knee, but did the wholesale selecting proximate vertexes and quickly assigning attachments above the joint to get things moving along.
I have had two weeks to percolate questions. I don't mind revising the model or sim settings so please suggest away.
My main question regards collisions. As you can see from my video, I am having trouble getting collisions to work as I would hope. I need to learn how to get real nice collisions. I want the leg when folded to look very natural. I discovered one thing, I had a very low res knee-cap, and it wouldn't collide with the femure at all. I doubled the polys and it mostly doesn't penetrate until it is really forced by the extreme pose. I also am getting hamstring muscles going through the calf heads when the leg is severly folded. Is there an approach to improving the collisons? A way of determing the mesh resolutions I need? Does the tet size matter here?
Second is the knee tissue and ligaments. I haven't gone past the main muscles yet, I will look into those, while I was considering what they might look like, I had an idea (lightbulb!) to make a knee "sheath" (see image) that would really be invisible but could also combine all of the attachements of the knee muscles into one sliding circular band of tissue (perhaps in addition to bone attahments). In other words, it would be a bit like an invisible knee brace that would have the outside of the knee muscles attached to stabilize the muscles at the joint. Could this be turned off but still hold the attachments for the sim? Sort of like digital invisible Spanx? It could be set not to inform the later facia and skin? I am wondering if an approach like this could be useful.
I hope to get into facia and skin sim on this leg before my 30 day trial expires. I am going to have a simple tube of facia/skin that runs from the thigh down to the heel. I understand that this will be a double-sided watertight model that is bridged at the top and bottom. I can model this next weekend. When I tested Z cloth in order to make the Knee sheath geometry, the top and bottom rows of polys were "pulling" and were not clean topology (see image). No big deal, I deleted the top and bottom rows and then bridged and made my sheath geomtry. The facia/skin will not be able to do this. I want the top and bottom edges to look nice. Is there an approach for pinning the edges of the cloth during the sim? I will have a big hole and a ring of bridge poly at the top of the thigh. Or do you turn off the visibility of the end rows of polys somehow to hide the messy part? Under a sneaker or some such?
Thank you all for your help so far and for this excellent plugin, I think that's all for now.