Offset Normals On Animation

[aracid]

Hey all

Im importing a sequence of OBJS with normals, I want to change the normals so that they face down, {0, -1, 0} and I want the Normals to rotate with the object as the object starts to rotate, so basically stay orientated to how they were on frame 100.

if the object rotates 90' clock wise, then they should face to the left etc...

I thought by taking the difference between {0, -1, 0} and imported N, then adding that to the normals again would surfice, but it didnt seem to.

to give u a rough idea of what this is for, Ive got an object sequence from XSI and at a point they all freeze, hence why the ice grows down the Y normal, then the objects start moving again, its automatically orientated to the imported obj sequence.

any ideas for this normal issue would be great :-)

thanks again

brian

[edward]

I assume you mean point normals. What about just using a Cache SOP to cache frame 100 or use a File SOP that only loads frame 100, and then copy the normals over into your current frame geometry?

[MIguel P]

Well, I was doing tests, but I have a small mistake... I don't know what.

I think you must use the dihedral function (align VOP, or dihedral() ) to orient the vectors. I will try it again...

[MADjestic]

[quote name='MIguel P

[lisux]

If you need to orient your normals in any direction you can use a VOP definition to create a new SOP and into it use tha Align VOP and to rotate your normals to point to your direction.

Is the same approach gived by Miguel but using VOPs instead of directly expressions or VEX.

If you only need to force your normals to point towards (0, -1, 0) use the approach majestic suggested.

[old school]

AttribReorient SOP.

From the Help:

"The Attrib Reorient SOP is used to modify point attributes based on differences between two geometries.

The Attrib Reorient SOP computes rotations for each point in the selection by examining differences in surface normals and tangents from the reference geometry to the live geometry. The named vector and quaternion attributes are updated by applying the computed rotation to the attribute values in the reference geometry."

Works with any attributes. Just lock of the right input (or make sure that it is static). Example use: painting fur attributes on rest geometry then applying to sequence of deforming geometry imported from <said> package.

[aracid]

AttribReorient SOP.

Hey all

thanks soooo much for the comments,

old school --- thats exactly what im looking for :-)

thanks again guys

brian