normal transfer from another object (help)

massta

Captured points from a grid using a sphere.
Sphere is animated and I'd like to transfer the sphere's normal (a single point) to all the points being captured.

Thus emitting particles with an animated normal from a second object.

See attached file.

Not sure if I should transfer the normal to the group in SOPs or grab the normal in POPs.

Thanks,
~Shawn

massta · Posted: Sat Jun 07, 2008 5:17 am GMT Post subject:

Thinking I need to take a good look at the Attribute Transfer SOP.

Allegro · Posted: Sat Jun 07, 2008 12:09 pm GMT Post subject:

You can use the point sop!

massta · Posted: Sat Jun 07, 2008 5:21 pm GMT Post subject:

Hey Allegro,

Thanks for the help. Your example works even if I change one sphere to a grid.

When I try your method with my animation, I get nothing. Take a look (attachment).

I think the problem lies with changing input of points from the group1.
I need the point sop to cook every frame or something.

Thanks again,
~S

SYmek · Houdini Master Joined: 13 Mar 2003 Posts: 935

Yellow/black zebra on node means warning! PointSOP requires two inputs to have the same number of points (or even be identical?). You need here Attribute Transfer SOP or some magic VEX if you need greater control on this process. I modified your scene. Hope this is what you're after.

cheers,
sy.

geneome · Lurker Joined: 04 Mar 2008 Posts: 11 Location: Maryland/DC

So what you're trying to do is use an animated sphere's normal to dictate the grid's normal direction within the sphere's bounds, then, use these new grid normals to change the direction of particles generated from the grid right? If you want to use the normals of each point on the sphere then SYmek's got it. (I cleaned it up for myself to see it in action so I'll post it here.)

But if you are looking to use a single normal for the whole sphere (which seems to be the case from from your first post), you could use a primitive sphere (single point) instead.

massta · Posted: Sun Jun 08, 2008 4:04 am GMT Post subject:

geneome and SYmek, you rock!

This is exactly what I was shooting for. I looked into using a primitive sphere but I couldn't add a Normal to it (not with Point SOP or Primitive SOP).

Anyway, it was just easier to group/delete so I could select any point I want to use for a normal transfer.

You can see inside my file what I was aiming for under the second particle sop.

Thanks!!!
~Shawn

geneome · Lurker Joined: 04 Mar 2008 Posts: 11 Location: Maryland/DC

This is such a great example of the procedural workflow... definitely video tutorial worthy. Thanks to SYmek for pointing to the right answer!