I'm rendering hair attached to some poly surface.

Use the following to get hair tangent direction:
vector Tangent = normalize(dPdt/Dv(t));

But using dPdt/Dv(t) or just dPdt seems to produce different results depending on point of view.

I.e if I rotate the camera around hairs then I get some other results for my tangents.
But hair tangent direction in world coordinates should not depend on camera position.

How can one get camera independent hair tangent?

sergey_sh
I'm rendering hair attached to some poly surface.

Use the following to get hair tangent direction:
vector Tangent = normalize(dPdt/Dv(t));

But using dPdt/Dv(t) or just dPdt seems to produce different results depending on point of view.

I.e if I rotate the camera around hairs then I get some other results for my tangents.
But hair tangent direction in world coordinates should not depend on camera position.

How can one get camera independent hair tangent?

Isn't dPdt in camera space, which is a current space for most surface context variables?

SYmek
Isn't dPdt in camera space, which is a current space for most surface context variables?

Yes. So perhaps you're looking for the *transform(to_space,vector) [sidefx.com] family of functions to transform the “current space” (which in Mantra this is the same as “camera space”) tangent vector to “world space” (which corresponds to /obj).

So, maybe something like:
vector Tangent = normalize(vtransform(“space:world”,dPdt/Dv(t));


Cheers.

Thanks SYmek, forgot about it.

vector Tangent = normalize(dPdt/Dv(t));
Tangent = vtransform(“space:world”, Tangent);

This works.

Thanks, Mario. Just saw your message after submitting mine.