First Post - transfer primitive attributes on scattered points, and mo

[fretwizard]

Hi Everybody!

This is my first post in this forum

I've started studying Houdini 10 one month ago and I thinkg it's very cool. I'm trying to test some procedural modeling techniques in order to create my own digital assets.

I have some of questions for you guys.

- I scattered some points on a poligonal mesh, now I want to store some primitive attributes on the scattered point. For example, for each single scattered point I want to store the poligon number on which it has spawned (attributeTransfer SOP?).

- I would also like to know how can I access bounding box information (the ones shown by houdini when I mid-click on a node). I want to store on each single poligon of the mesh its own bounding box min and max vectors. What I managed to do so far is using the "forEach" SOP to iterate a Bound SOP on each poligon. But with heavy poly meshes it gets very slow and anyway I only got the bound objects, not the vector values.

- Is it possible to use the paint tool on UV texture files instead of attributes on vertices? How do I set it up?

- Is there a way to paint attributes on points that have been added to the mesh with a 'scatter' or 'add' SOP. Even if I keep the original geometry after the scatter I can only paint on the original geo points, not on the scattered ones.

I hope I don't ask too much, it's just I have something very specific on my mind.

Any advices are welcome. I have a nice RSL background so if you wanna suggest to do something in VEX or expressions you're more than welcome (I didn't learned it yet though).

thanks in advance

[symek]

- I scattered some points on a poligonal mesh, now I want to store some primitive attributes on the scattered point. For example, for each single scattered point I want to store the poligon number on which it has spawned (attributeTransfer SOP?).

no need to use attribTranser:

- create uniques points for your polygons (facetSOP)

- create explicite prim number attribute on primitives via attribCreateSOP -> $PR as integer primitive attribute value

- use attribPromoteSOP to promote this attribute to a point type

- scatter point on this prims

from now on, scattered points will hold primitive number attrib they belong to.

- I would also like to know how can I access bounding box information (the ones shown by houdini when I mid-click on a node). I want to store on each single poligon of the mesh its own bounding box min and max vectors. What I managed to do so far is using the "forEach" SOP to iterate a Bound SOP on each poligon. But with heavy poly meshes it gets very slow and anyway I only got the bound objects, not the vector values.

generally there is a bbox() expression to get bounding box data. You can search for interesting expression in texport using:

exhelp -k keyword command. Very handy. Bounding box is also avaible as a local variable in many nodes. Plus, you can access this data in vopSop. I would use bbox() or local vars inside forEach SOP. Alternatively I would try a loop in vops (or vex), which will be a way faster, but I'm not sure if SIMD thing would work well with computing min/max for group of points (looping over all neighbours).

- Is it possible to use the paint tool on UV texture files instead of attributes on vertices? How do I set it up?

You mean you want to paint raster images, not attributes on geometry? Not possible I'm afraid (other then painting on a dense grid with 1:1 pixel to point ratio ).

- Is there a way to paint attributes on points that have been added to the mesh with a 'scatter' or 'add' SOP. Even if I keep the original geometry after the scatter I can only paint on the original geo points, not on the scattered ones.

You can append addSop after scattering and add a weird polygon (select Polygons->ByGroup Tab). This way PaintSOP will see your points. After painting is done, you can remove this polygon crap.

hope this helps!

example.hip

Edited November 15, 2009 by SYmek