# guache

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Peon

• Name
Joseph
1. ## Hair: "helmet hair" and scalp penetration

Two questions about hair: 1) I'm trying to get a "helmet hair" look, i.e. a hairdo that has been "pushed" closer to the scalp. I can always modify the guide curves by manipulating them as SOP curves, but I'm wondering if there's an dedicated groom (either tool or process) that would push an existing hairdo closer to the scalp. Or should I perhaps start with guide hairs that are already near-tangent to the scalp and try to create the "helmet hair" look from there? 2) While working on the problem above, I often get hair penetrating the scalp. Is there any setting in the groom tools that would force hair to always stay outside of the scalp (without doing simulations)?
2. ## "Tent": Connect 1 pt to a bunch of others pts

Thanks for all the replies. The points on the ground are already sorted by angle w/r to the "peak". I ended up with this: Add SOP on the ground pts to construct a ground poly scale a copy of this poly down to zero at the "peak" point i.e. collapse all points of the copied poly to one point location Skin SOP the two polys: the multi-point "peak" and ground poly to construct a tent Fuse SOP on the "peak" point to get just one point there I wish there was a SOP does this "cleanly", in one go.
3. ## "Tent": Connect 1 pt to a bunch of others pts

I want to create something like a tent: I've got one "peak" point and a bunch of "ground points" and I want to connect them into a "tent" with triangular sides, all meeting at the peak point. What's the cleanest, most elegant way to do this? I can loop through the ground points to construct each triangular section one by one, but I was thinking there's a native SOP that can do this for me.
4. ## Signed angle between vectors in VEX

Cool, thanks.
5. ## Signed angle between vectors in VEX

In Vex, I'm trying to find a signed angle between two vectors i.e. an angle which treats one vector as a "base" and the other as a rotating "clock hand", so that I get positive angle for a concave angle between the two (0-180 deg) and a negative angle for a convex angle between the two (180-360 deg). The dot product on normalized vectors gives me the angle, but it's symmetric. Is there a trick that gets me the sign?
6. ## Export Pz *with* displacement

When exporting image planes, how do I include displacement in Pz? My surface has a displacement towards the camera. Right now, in Pz I'm getting the z depth to the surface itself, no displacement. Can displacement be incorporated in Pz or do I need another export variable for that?
7. ## Colorize volume by 3D location

Thanks, exactly what I needed.
8. ## Colorize volume by 3D location

In Houdini, can I colorize a volume (either VDB of Houdini volume) based on the voxel location in space? E.g.if I have a cube-shaped volume, can I color its quadrants differently?
9. ## Foreach loop per primitive but with accumulating ray geo

I have a Foreach loop which processes a bunch of primitives, one-by-one. Inside the loop I have I a Ray SOP. For its target geometry (i.e. what I'm projecting on), I want to use the original target geo (coming from outside the Foreach loop) plus all the projected primitives processed so far, i.e. the progressively accumulated results of previous projections. I don't want the loop as a whole to work in "feedback" mode i.e. working on previous iterations. I want the loop to process primitives one by one. I just want the to Ray SOP to accumulate iterations (previous projections). Any advice how to arrange this?
10. ## Vector disp.: overhang possible?

Sculpting packages like Z-brush can create surface detail which sometimes has some slight overhang (like folds etc). With the vector / tangent displacement tools in Houdini, can I create (or work with) a disp map that would create a slight overhang? The pic shows a flat base plane for clarity.
11. ## Faceted displacement

I'm getting a faceted appearance using a disp map, corresponding to the pixels in the disp map. Any way to smooth this out *without* increasing map resolution, increasing shading quality etc? Do I need to create vertex normals from the displaced geometry normals somehow? The displacement map is a float exr image, so color depth is not a problem. The vex code doing the displacement is as follows: vector mapclr=0; float mult=1.0; mapclr=texture(map,s,t); P+=mult*mapclr.r*normalize(N); N = computenormal(P);
12. ## Hexagonal mesh

Very clean hexes, thanks.
13. ## Slice a SOP at reg. interval in cam space

I have a cam looking at an object. The cam is stationary, but it's rotated (not aligned to XYZ axes). The object has no xform. It has a part at the SOP level, part A. How can I slice part A in cam space like an egg slicer: ie. add parallel divisions/edges across it at regular intervals? One idea would be to xform the part by the inverse of the cam matrix, SOP Divide (Bricker), then put the part back in place. If anyone has better ideas (either for cam space xform or the slicing method), I'd love to hear them.
14. ## Hexagonal mesh

Thanks. The Voronoi hexes are a bit uneven. In Copy, a Z offset of 0.56 (rather than 0.5) gives better results. I'll try to fix the hexes by snapping to tri grid.
15. ## Hexagonal mesh

Thanks. To be more clear: I don't need to divide an arbitrary 3D shape into hexagons, I just need a flat, roughly square surface made of hexagons. I can always use a Copy SOP, but I thought there could be a "smarter" way. EDIT: Never mind, I got it: start with a tri grid, then blast away the centers of hexagonal areas.
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