(... continued)

Then I looked into friction. The concept of Static and Dynamic friction is sort of understood by most people: Static holds the cloth in place until the 'driving force' gets too large, and Dynamic works against the driving force when the cloth is moving. Both are independant of cloth density, and Dynamic friction is independant of cloth speed (unlike for instance air damping). 

In the books, both are modeled as ratios between forces, no units to convert. The literature values for Static are similar or a bit higher than Dynamic, and range from 0.04 (teflon) to over 1 (iron/iron on railroad tracks etc), something on skin goes for about 0.7 and some cloth-to-cloth might go for 0.3, and anything in between.

Dynamic friction in Poser is slightly different, and although it's independant of speed and density, it's not a ratio between forces but a material-dependant acceleration by itself. However, taking unit conversion (to cm and frames, like the gravity constant) into account, we can quite safely put in the literature values as a happy coincidence.

From tis we can infer that the Poser default value 0.1 is not too bad for cloth over a wooden table, but is far too low for cloth over cloth or skin. Good for Cloth Room, not too well for Clothes Room :). Values up to 0.7 are recommended.

This is for higher cloth speeds (> 10 cm/frame) only. At lower speeds its effect decreases and the results are effected by Static friction as well. This might be a good idea from a simulation point of view, but it's not according to the books.

Static friction in Poser is entirely different from real life. It prevents the cloth from moving indeed, not effected by Dynamic friction, but there is no relationship (discovered yet) between measured values and the literature ones. The concept fits but the model does not. So for those who want to match cloth behaviour to life of want to match Static to Dynamic, a translation table was provided. 

From this we can infer that the Poser default 0.5 is not too bad for cloth over a wooden table but could be raised to say 0.85 for cloth over cloth or skin. But for smooth materials with Dynamic values as low as 0.3 or 0.1, the accompanying Static must be reduced to 0.1 or far less.

Another observation is that Static plays a role on moving cloth as low speeds. This is not what one expects from the books. So, in order to improve image or animation results one not only has to take care of Dynamic but of Static also.
Unfortunately, this "low speed range" (1-10 cm/frame) is very common in our clothing use of the Cloth Room, and the meaning of the dial-values for both are very different. Since friction plays a relevant role in the interaction between cloth and figure, this is the place where our artistic / alien experience or gut feeling will creep in.

Finally, Cloth self-friction is a mystery to me as no change in value provides any effect on any result in animation or final image. I have no fit for even the concept.

So, stretching will be next.

- - - - - 

Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

visit www.aRtBeeWeb.nl (works) or Missing Manuals (tutorials & reviews) - both need an update though