Simulation Rig Build
The idea here is to have a rig that is a container for all our geometry inputs, cloth objects, constraints, finalling and outputs. The rig is always built at world zero, with bind pose geometry and as clean as possible.
Building the rig is done in stages, all of which can be scripted up. It’s an incredibly click heavy process making sim rigs and I would advise anyone really wanting to get into the creature FX side of the industry to really learn to write python. The scripts don’t have to be complicated, several of my scripts are essentially ‘Click reducers’. I have made so many rigs that having a suite of tools to reduces the monotony of rig builds. Get the computer to do the heavy lifting and use the time doing the cloth development work.
The simulation rig is made up of a lot of groups and depending on the complexity of the rig you will fluctuate in the number needed. Boxer has one main cloth geometry, his shorts. In Boxer I simulated his boot laces but to keep this simple I’ve decided to focus on his shorts. It’s a lot of groups but it helps to organise the rig and the colour scheme will become apparent when we build our display layers.
Here is the rational behind the rig structure.
rig_GRP All simrigs will be referenced in the cfx scene and the namespace will give the rig a unique name.
cfx_CTL used to move the rig in the scene and can carry additional attributes.
connectToAnim_GRP contains the geo that will connect to the animation cache via a blendshape.
sim_GRP contains the geo converted to nCloth and houses the nucleus.
dynamics_GRP contains the contraints, colliders, rigid bodies and fields.
finalling_GRP contains geo that is blendshaped to both the connectToAnim and sim geo.
output_GRP contains the high res geo which is wrapped to the low res geo.
I’ve simplified the sim rig structure a little, the idea is to scale up the complexity when needed. The body and shorts geometry should be imported. Each piece of geometry is duplicated 3 times and are renamed after the group they are housed in.
The body geo, duplicated 3 times and each piece receives a new suffix
body_CtA, body_simIN and body_FnL.
The shorts geo is duplicated 3 times and each piece receives a new suffix
shorts_CtA, shorts_simIN and shorts_FnL.
This is the basis for for the rig, we will bring in the high res render geometry into the rig near the end of the build.
The simIn geometry will also receive an additional suffix when converted to a cloth object.
nucleus_GRP houses the nucleus.
wrapBase_GRP contains all the Base geometry Maya generates from using a Wrap Deformer.
It’s also a good idea to not change the name of the nucleus. If you do and create a new nCloth object Maya will assume that there is no nucleus present in the scene and therefore generate a new one called nucleus1. I found changing the name was far more trouble than it was worth.
The output_GRP is where we will put all the high resolution geometry. The shorts have a several additional pieces of material that I opted not to simulate. These will be wrapped to the finalling geo and exported. The wrap deformer in Maya creates a wrapBase mesh which we parent to the wrapBase_GRP, for housekeeping.