Making instances respecting the point geometry normals?

[oldiesgoodies]

Hi

I am rendering a scene where I am instancing some geometry over a point instance object(it only has points). Everything seems to work fine, except making instanced objects to respect the geometry point normals. My point object has normals.

Any suggestions?

thanks

[pclaes]

Do you have any other attributes overriding your N?

Specifically orient or up could change the alignment of the instances.

This is the order of preference:

orient -> up -> N -> V

Did you create the normals with a sop or inside a vopsop? Make sure your N is a vector not a float[3]. You can check this in a spreadsheet and see if your data is N[1],N[2],N[3] (this is the float[3] representation) or Nx, Ny, Nz (this is the vector representation).

Also make sure your normals are not zero.

[Macha]

Peter is absolutely spot on of course.

One thing to add though. Not sure I'm completely right (please correct me if it's wrong) but I think the orient attribute is a quaternion, so the first 3 components are the axis and the last should be the angle. That could be confusing otherwise.

[oldiesgoodies]

Hi

Thanks for the help. I will check out my scene to see what is going on.

I have one more question regarding render tiem instances. HOw can I randomize the scale of the instances?

[pclaes]

"orient" is a quaternion - and yes, the axis is first, then the angle.

I think the only difference with "rot" is the order of operations. I think orient happens first, then scale and translate and then rotate:

http://www.sidefx.com/index.php?option=com_forum&Itemid=172&page=viewtopic&t=6679&highlight=copy+sop

in regards to the scale:

you should be able to use both the pscale (float) attribute as well as the scale (float[3]) attribute

-> haven't tested this, but should work - otherwise there are other ways around it with delayed loads and instancepoint() expression:

http://www.peterclaes.be/blog/?p=34 (hip files at the bottom)

(in the same way you use the attributes with the copy sop .. that's why it is a good idea to prototype point-based instancing with the copy sop - and far fewer template points).