Joint rotation axes and limits / constraints

[Esteve]

Dear all,


I want to use MakeHuman to generate models of humanoid robots in Blender for a research project. I want this model in the URDF file format common in robotics application.
Therefore, I already converted the mesh vertices in disjoint rigid bodies.
However, I need "classical" rotational joints and their constraints, i.e., their joint axis and if possible, the allowed min/max values. If a joint has multiple degrees of freedom (shoulder), I can substitute it by chaining single rotation axes.

Does anybody know a way to determine the correct rotation axes and joint limits from any of the MH rigs? I tried all provided in the MHX2 importer (overriding the exports) with no luck.

Any hint is appreciated and please apologize if I posted in the wrong category

Best
Esteve

[blindsaypatten]

I don't think that MH sets any limits on the armature, it will let you do any crazy thing you want. It seems to me that what you really want is the axes of rotation and limitations of human joints rather than MH joints and should be looking for general information on human joint movement.

[Esteve]

I don't think that MH sets any limits on the armature, it will let you do any crazy thing you want. It seems to me that what you really want is the axes of rotation and limitations of human joints rather than MH joints and should be looking for general information on human joint movement.

Hi and thanks for the answer. You are basically right regarding information on human joint movement. However, MH uses parametrized human models so position of the axes (and maybe even the orientation) might change with age for instance. From the perspective of robotics, having a formal definition of joint axes could greatly simplify the inverse calculus for instance. I see that it is maybe less important for artistic use cases.

Can anybody confirm that this information is not included in MH?

[RobBaer]

Can't confirm beyond a shadow of doubt, but I am unaware of anywhere within the code that constraints are implemented. It is as you say an artistic tool, not an engineering model.

There is the ability to implement your own constraints in a downstream program like Blender, and Thomas has some discussion of this in the .mhx documentation, the predecessor to .mhx2: https://thomasmakehuman.wordpress.com/m ... e-mhx-rig/ As I understand you are looking for values, though, and are looking for guidance in terms of numbers. Don't think they exist here.