Delta relative to tangent space

[Gianluca Siciliano]

Hello guys,

still me trying to understand how Houdini works 

I basically would like to calculate the delta between the points of a target geometry and a reference same topological mesh in the tangent space of this reference geometry.

I quite tho do not find a mathematical way to calculate it using vex.

Any idea?

Thanks

 

[Feather]

By tangent space do you mean along the curved surface of the geometry or literally like a tangent plane of each point on the mesh?

[anim]

you can compute UV tangent space direction vectors on geo using Poly Frame SOP (few modes for that Texture UV gradient, Attribute Gradient,  MikkT)

then you can construct matrix from them and use for whatever you need

 

you can also use Attribute Reorient SOP to apply sort of tangent space delta between 2 meshes to any vector or quaternion attribute, which may be easier that computing everything yourself, but it really depends on what you are doing

Edited February 7, 2020 by anim

[Gianluca Siciliano]

1 hour ago, anim said:

you can compute UV tangent space direction vectors on geo using Poly Frame SOP (few modes for that Texture UV gradient, Attribute Gradient,  MikkT)

then you can construct matrix from them and use for whatever you need

 

you can also use Attribute Reorient SOP to apply sort of tangent space delta between 2 meshes to any vector or quaternion attribute, which may be easier that computing everything yourself, but it really depends on what you are doing

Yep this is exactly what I might need...I will try thanks.

 

I am trying anyway to recreate the concept of tangent space blendshape like in Maya so I needed the correct way of calculating the delta between two meshes so I can then use this to update the point position of my source