Physique-ing

Making your mesh move with the avatar
(C) Malard 2009

This tutorial will explain how to physique your mesh so that the mesh will move in harmony with the avatar body.

Pre Weighting

Ok first off, select your mesh then go to the modifier list and select Physique. Go to Physique's properties list and then select the Attach to node button , the first one on the left. Go to the groin of the Avatar and select the blue cube (pelvis node). A window named "Physique Initialization" will show up. In it, we need to set a couple of things but not many. In the "Vertex - Link assignment" list section, set the following

Overlap	0
Smooth	10 (max figure)
Fall off	0

press ok and you have made the first stage of weighting.

check that the physique has been process correctly by moving the animation bar a couple of frames and watch the avis right hand side of torso (respective of the avatar). You will notice that certain areas will cross collide. This is due to weak links and we will need to change a few of them in physique in order to get a satisfactory weightment.

Real Weighting

Now as we have a mesh that is pre weighted, it isn't too difficult changing the settings of the links. A couple of recommendations:

Ok now that's said, down to the business. Move your animation bar to frame 9 and you'll see the avatar in an impossible pose (lol) should be like a jump position. You should also notice that your mesh may be not showing correctly on some areas especially at the top of the pelvis (if its a dress or long top etc). That's our first port of call.

Each bone will have a link between its tips that connect to other tips  of other bones in a series. You will see a little further on that you will be able to see these links and use them to adjust settings.

The first two bones above the pelvis node and the pelvis node itself have the links that cause the cross collision of the mesh above the pelvis. So first off activate Physique and then in the physiques selection list, select "Envelope":

Now that is selected you should see now that the bones (in the front view port as wire frame) should have yellow lines and yellow crosses at the tips of them. These are the links between the each bone and they govern how the vertices move hence the name Envelope. Since we now know where the links are (roughly since your mesh could be in the style of malardorian), click on one of the links and list of properties should show up:

The most important controls we will be adjusting are Radial Scale, Parent Overlap and Child Overlap. Both Inner and Outer Envelopes will be adjusted but usually the only envelope that is needed to be adjusted is the outer. We also need to adjust Strength and Falloff. Strength and Fall off work regardless of the Outer and Inner envelopes.The Falloff changes the reaction curve of the vertices assigned to that link. a value of 1.0 makes virtually every vertex show red meaning that the relative strength of those vertices assigned to that link are nearly always in the same relative position to that bone. Think of it as a Geostationary satellite (vertex) moving in sync with the earth (link). Where as if the fall off was 0.0 then the vertices strength would be very low. You can think of this affect as being someone holding a slinky at one end (link) and letting the un-held (vertex) droop. When ever the person move their end the other end lags behind and eventually gets to the correct position. Strength governs how strong the links connection with the vertex is. It could be look at as the limit of strength the fall off will work at.

At the top of the menu you will see something called Selection Levels. They are (in order of left to right) Link , Cross Section and Control Point. In certain situation you may want to make an envelope affect a certain area of vertices not a standard all around selection. Control points will allow you to accomplish this by simply selecting that selection level and then selecting the control point and moving it in the general direction you want to make the envelope affect. You can also select multiple control points. Cross Sections are used to adjust the sharpness of the envelope. When you first select an link the envelope will show like a pointy oval. If one was to move the Cross Sections to those points then the oval shape will change to a more of a cylinder shape, yet again changing how the envelope affects the vertices movements. Link is the one we will be using most of the time since most of the problems that show when pre physique has just be done, will be solved using this Selection Level.

Ok enough of the background info time to do some physique-ing! With your link selected, increase the Falloff to max (1.0). You should then see that some of the cross colliding area is returning to normal. Repeat this for the bone above the pelvis node and for the pelvis node itself. You should have fixed that area now! The second port of call is the legs. This is the most fragile yet important part of physique since one small adjustment can nudge you right off course if not careful. The rule of thumb when ever physique-ing the leg area is to ALWAYS have both left and right leg links selected at the same time. Remember that the body is symmetric so you'll want to keep your mesh symmetrically moving as well.

At this point change animation bar to frame 15. This is the worst frame since it will bring out a load more cross collisions. But we will fix the cross collisions on the top part of the legs. Since the legs are one of the places were Falloff is not advised here but there is another way to overcome the cross collisions being seen. Because all the outer envelopes have a radial scale of 11 this is effectively blurring the Falloff range of both leg links and causing them to merge together. We want to "sharpen" those fall of ranges, so we need to reduce the size of the envelopes. Now, select the Button saying Outer and then with both the links of the top part of the legs selected, change the Radial Scale to about 2.6. This should make the mesh around the legs fix themselves in the correct area. You may need to fiddle with the strength of the links so the clothing mesh is at the correct distance from the leg meshes.

You may also need to adjust the effective length of the envelope to allow another envelope more relevant to correctly align other vertices. This is done with the Parent and Child Overlaps. Parent Overlap is the pointed end which is closes to the large end of the bone that the link is related to. Child overlap is the end closes to the pointy end of the bone that the link is related to.

So all in all everyone can physique, its just understanding how it works and what you can do. With what you have learnt in this tutorial, you can also apply to any other bones in the avatar AND on your own bipeds.