Hello team,

I can not find any explanation for "Tendon Mass Density Scale" in help doc.

If I set 1 to the attribute, the sim of the muscle will be like the image 001 below. The tendon area is more Stretching than setting it to 50.

I guess it is like the Mass Density. Higher mass density correlates with higher hardness， so it is less strength in image002.

If my understanding is incorrect, please correct me. Thanks.

TendonMassDensity Scale will multiply with the muscle's solid mass density using the TendonMask as a mask. ie only tendon regions (the white areas) will receive the mass density scale.
It does not affect hardness. Increasing mass in Vellum in this context has the interesting side effect of "raising priority" for the stretch convergence. It doesn't really raise priority. In areas where mass density varies, there will be less stretching where mass is greater.

Thanks for your help.

So you mean, it simply increases the density of this area by multiplying the mass density, without increasing the hardness of this area? Is the increase in hardness just a byproduct?

Generally, increasing density typically leads to an increase in mass. If two objects have the same volume but one has a greater mass, it may be harder. This is because a greater mass typically means more material is compressed into the same volume, thus increasing its resistance to external stress. Greater mass may lead to higher hardness.

But I am not sure if vellum follow the rules.

chen_chen
But I am not sure if vellum follow the rules.

Vellum follows the rules of XPBD.

Basically, giving a point more mass enables it to win more often in the tug-of-war that happens when multiple constraints push and pull point locations around. It has little to do with how much material is compressed into a volume.

Regarding the a tendon's "hardness", there's an additional MuscleProperties>Tendon Stiffness parameter that scales the stiffness according to the tendon mask. So tendon regions are stiffer than muscle "bellies" by default, and less prone to stretching/changing shape.
The ability to vary the mass density and the shape stiffness in tendon regions comes from two separate parameters.

Increasing density typically leads to an increase in mass. Material is compressed into the same volume, It will be hard in physics. Greater mass enables it to prevail during stretching in vellum. The result is same. Vellum utilizes constraints to achieve physical effects.

I tried the tendon stiffness. I need a big value.

BTW: Can I use muscle paint node before muscle properties? Do I need the muscle constraint properties vellum initialize all the constraints first?

Thanks

chen_chen
BTW: Can I use muscle paint node before muscle properties? Do I need the muscle constraint properties vellum initialize all the constraints first?

Best to add MusclePaint at the end. Otherwise the nodes can overwrite the same attributes.

Thank you for your prompt reply.