Author: admin

Archived post by rich lord

I’ve been needing a bunch of pattern based, seamless textures, so I made a couple of tools to help me make them fast. They are pretty crude. This first one tries to make the scatter tool seamless by relaxing points, and copying any overlaps onto its opposite side. These points get pinned, and any internal ones get a final relax. It works OK, good enough for what I need.

Heres the hip

Then I did another version following the same idea but with RBDs. I used @mestela ‘s trick of scaling up the rbds to create an initial packing, then processed them similar to the scatter version.

Heres the hip for this one

Gifs of the pieces scaling up look great

Attachments in this post:
http://fx-td.com/houdiniandchill/wp-content/uploads/discord/20185602/22/18/a5.jpg
http://fx-td.com/houdiniandchill/wp-content/uploads/discord/20185602/22/18/18_02_22_seamless_scatter.hiplc
http://fx-td.com/houdiniandchill/wp-content/uploads/discord/20185602/22/18/a1.jpg
http://fx-td.com/houdiniandchill/wp-content/uploads/discord/20185602/22/18/18_02_22_seamless_rbds.hiplc
http://fx-td.com/houdiniandchill/wp-content/uploads/discord/20185602/22/18/gif02c_scale_packing.gif

Archived post by TOADSTORM

so what you’re trying to avoid when you’re dealing with mushrooms is a smooth pressure front. the project non-divergent step of the smoke solver computes the pressure field, and when you have areas of high density right next to areas of low density, like at the beginning of a smoke emission, the velocity field is going to be more or less “combed” straight out along the gradient of that pressure. short answer, you get mushrooms.
so what you want to do is mess up that velocity field a little bit in order to encourage smoke to swirl around a bit, along that pressure front. the way i like to do it is in a sop solver. use the sop solver to import the `vel` data from your smoke object. when you jump inside, you’ll see the `dop_geometry` node is importing that field. copy this node and change the geometry data path to `pressure`. we’ll use this pressure field as a mask, so we can only mess with the velocity field exactly along the “edge” of the pressure field. use a volume wrangle on this field to isolate just the edge like so: `@density = fit(@density, 0, 0.1, 0, 1);`. make sure “bind each volume to density” is enabled. now we can scatter points along the “edge” of the pressure field in a scatter sop.
next, use a vdb from particles to create a fog vdb around these points. the goal is to use this field to “punch holes” in the velocity field, like swiss cheese. convert the vdb into a standard volume, then use a volume mix sop to invert the volume (set the mix method to “user”, then value to `1-$V`). then post-add a small amount, like 0.3 or so. what this does is make it so that most of your volume has a value of 1, but the holes will have a value of 0.3. then just multiply this against your `vel` field in another volume mix.
the end result should be that the velocity field has holes punched in it, but only around areas on the edges of the pressure field, which should help break up mushrooms without disturbing the rest of the simulation.

Archived post by eetu

@matte @aswaab `Tiny little points will be hard to sample within a pixel and cause noise. If you put a floor under how small they can be in pixel space (and maybe compensate by lowering alpha etc) that might make it cleaner` there is a mantra property for exactly that, *vm_geofilterwidth*

Archived post by mestela

ugh, my brain is mush tonight… whats the node to convert groups back to attributes, like a connectivity sop?

i’ve selected polys, given them random colours, partition to make them groups, now i want the groups back to attribs

hmm, or vex this and define my own attribs via hsv…

yeah that worked, woo

well goddamn, someone mentioned this at work today, just tried it

“`setprimintrinsic(0,’pointinstancetransform’,@primnum,1);“`

do that on packed prims, orient will now rotate them automatically, no bollocks of having to manually update intrinsic transforms

Archived post by dchow

“`int pp0[] = primpoints(0, 0);
vector prpos = prim(0, “P”, 0);
vector pos0 = point(0, “P”, pp0[0]); vector pos1 = point(0, “P”, pp0[1]); vector pos2 = point(0, “P”, pp0[-1]);
vector v0 = normalize(pos2-pos0); vector v1 = normalize(pos1-pos0); vector v2 = normalize(cross(v0,v1)); v1 = normalize(cross(v2,v0));
matrix x0 = maketransform(v1, v2, prpos);
pp0 = primpoints(1, 0);
prpos = prim(1, “P”, 0);
pos0 = point(1, “P”, pp0[0]); pos1 = point(1, “P”, pp0[1]); pos2 = point(1, “P”, pp0[-1]);
v0 = normalize(pos2-pos0); v1 = normalize(pos1-pos0); v2 = normalize(cross(v0,v1)); v1 = normalize(cross(v2,v0));
matrix x1 = maketransform(v1, v2, prpos);
matrix output = invert(x0)*x1; @P *= output; “`

i think it’s that