The latest Ziva VFX release, version 1.4, include 2 new tissue parameters – Surface Tension and Pressure for Tissues – that will eliminate the need for a time-consuming fascia pass. These new “for tissue” parameters are essentially enabling the fat and skin passes, which are tissues, to achieve the dynamic effects associated with fascia, which is a cloth.
Just like before, you’ll want your skin model to be a closed volume with an inner layer, outer layer, and boarder. The Inner Layer is modelled using the cloth solver (this would be the fascia layer), the the Outer Layer is projected back to the skin layer using Wrap3 or similar tools, and lastly, the Border is the bridge between the two layers. Keep in mind, we aren’t removing the need for a fascia-like layer in your build, we’re simply removing the need to simulate it as a cloth and, instead, making it part of the skin/fat layer – so it is all in one and is much faster to simulate.
Once your character’s skin model is setup, you’ll want to convert the entire object (all layers) into tissue and add the necessary attachments. You can learn more about attachments here.
Now, the interior of the skin layer should be painted white while the exterior is black. This means that any changes you make to the material will only affect the white-painted areas (the inner layer!)
Now, if you play that back, you’ll see the collision proxy pair points that appear as green highlights, and you’ll see the skin mesh follow along nicely as the underlying anatomy moves. If there are any areas that are missing collisions – you may want to consider increasing the contact stiffness or making sure your ‘envelope’ is set up correctly.
Lastly, to improve the muscle definition on your character, use the new Pressure for Tissues function. Much like the Pressure for Cloth, this tool will help guide the tissue into the muscle grooves to decrease the amount of webbing between muscle groups.
Tip: If your character’s tissue seems to be inflating rather than wrapping tighter to the underlying anatomy, double check that you’ve entered a negative value.
One of the great things about Ziva Materials is that you can make as many of them as you want. So, if you wanted to increase the definition just under the arm or at a single joint area, where skin is often softer or tighter to the bone, you can simply make another material layer and apply greater pressure and less surface tension to form a deeper armpit.
The simulation speed improvements you’ll gain from removing the fascia layer and enhancing the fat/skin layer is highly dependant on your unique build. Internally, we've seen upto a ⅓ time reduction in complex simulations. If you have any further questions of the fat/skin workflow or wish to share your results with us, please contact us on the Ziva Community Form.
For myself I still solve the fat and the fascia separatly. but before using tissue as fascia layer you still need to model your fascia with cloth system like in te webinar. then you can extrude your fascia and convert it to tissue and simulate the fascia with a tissu or create directy your fat and keep the collision on with no fascia between your muscle and your fat. (hope I'm clear xD)
Was working on this creature Simulation for the past 3 - 4 months. Here you can see Fat and Fascia solved with coupled simulation method. I find the couple method more appropriate and convenient than the new ziva 1.4 (omitting the fascia and diminishing the pressure). If Fascia is omitted I am not getting the desired output. Maybe need to do some more tests. I will soon update the details of this breakdown process in my website with all tissue and material properties.