# mestela

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1. ## VEX quaternion to vectors

...and to finish that thought, now that you have a matrix, you can then take a vector that points along z, and multiply it by the matrix to give you your @N, and a vector that points along x to give you your @up. Example here: http://www.tokeru.com/cgwiki/?title=HoudiniVex#optransform_to_do_a_motion_control_style_camera
2. ## Sine waves color

http://www.tokeru.com/cgwiki/index.php?title=JoyOfVex13#Exercises but more generally http://www.tokeru.com/cgwiki/index.php?title=JoyOfVex In your case you could do something like float sin = fit(sin(d - @Time*4), -1, 1, 0, 1); vector col_hi = chv('col_high'); vector col_lo = chv('col_lo'); @Cd = lerp(col_lo, col_hi, sin);
3. ## a sharing system in Houdini??

wot tim said. sharing_emit_points.hipnc
4. ## Constraints mixing pops and bullet

That's really cool!
5. ## Creating fibrous language with attractor points

You deleted a wire in the setup:
6. ## Help With Speeding Up Render

That sounds like a nice repro to send to sidefx, good thing to poke Kai about.
7. ## Read only expression on left side of assignment

Works fine here, sounds like a stuck wrangle, happens sometimes. Try copying to a fresh wrangle.
8. ## Creating fibrous language with attractor points

Ha, I'd carefully balanced the emitters and forces to keep it 2d. On the emitters, set the variance to have some random y and z, that'll push it into 3d. Same goes for pushing the axis force spheres along z, they'll start to push particles off the 2d plane.
9. ## Scaling packed Objects with VEX

I have an example here: http://www.tokeru.com/cgwiki/index.php?title=HoudiniDops#RBD_deintersect_via_scaling_up_geo
10. ## Creating fibrous language with attractor points

Maybe this? Just a bunch of axis forces, point emitters, trails, and setting alpha so you get that multiplicative effect in areas of high density. trail_graph.hip

Might help:
12. ## Unroll a planar curve

Quite a few answers come up if you search for 'unroll' here. Several solutions in this thread: http://forums.odforce.net/topic/31600-spiral-unrolling-rolling-animation/?do=findComment&comment=174963

16 I think.
14. ## Pop attract with grains

set targetP, animate targetstiffness. grain_targetp_targetstiffness.hipnc
15. ## Noise never decreasing in VEX

Or this trick from Matt Ebb that doesn't require a solver: http://www.tokeru.com/cgwiki/index.php?title=Houdini_Vops#Noise_that_always_increases_with_cellnoise_vop
16. ## WIP - ok++'s softbodies RnD + .hip files

Did I say thank you already? I'll say it again anyway, thank you! Some incredible stuff here, can't wait to get some free time and pull these setups apart...
17. ## More Particles Following a PATH!

Something like this? I'm dumb and would need to see the geo of the spiral curve, but I'm sure the logic within here could be used to generate a spiralling force directly in pops. coil.hip
18. ## More Particles Following a PATH!

Also, a japanese houdini user wrote a great tutorial about a better pop curve force setup; google translate does a pretty good job, but you can also just grab the hips linked at the end of the article: https://qiita.com/taikomatsu/items/71d475541eb540705552
19. ## More Particles Following a PATH!

It should do that by default; if you have @v (and not @N or @orient), when you use a cop sop to copy geo to the particles, they should point their z axis along v. http://www.sidefx.com/docs/houdini/copy/instanceattrs.html Examples and gifs and stuff here:
20. ## difference between @Cd.r and \$CR

And that's another fun gotcha with houdini; if something is designed to read attributes directly (like the scatter sop is), you don't use the @ prefix. That also means that it won't understand the thing.subthing syntax, so Cd.r won't work either. Put down a point wrangle before the scatter, and create a new attribute which is just the red component, we'll call it red: @red = @Cd.r; Now in the scatter you can put 'red' into the density attribute field. It'll make sense in time, honestly!
21. ## difference between @Cd.r and \$CR

Dollar variables are hscript expression variables, hscript is sloooowly being phased out. At-symbols are vex attributes (@-ttributes, get it?), they're becoming the standard way to refer to geometry properties through most of houdini, its better to get used to that syntax. Occasionally you'll find some older nodes that only work with the older dollar syntax, best to ask here if you stumble across those. -matt
22. ## Shrinking Pieces inside of DOPS

The answer here was clashing names; the sops feeding into a pop source used to drive the rbd sim had static names, meaning when multiple copies of things all had the same name, and wrangles and whatnot were trying to update prim info, the system would get confused. Adding the current frame to the names in sops ensured everything had unique names (well, unique enough), kept it all under control. (assuming this is the same problem posted on discord, if not I can post the example scene we came up with)
23. ## Help With Speeding Up Render

Nice work Toby!
24. ## Learning VEX via Animated Gifs - Bees & Bombs

More inspiration: https://necessarydisorder.wordpress.com/2017/11/15/drawing-from-noise-and-then-making-animated-loopy-gifs-from-there/
25. ## Learning VEX via Animated Gifs - Bees & Bombs

Came across these great looping gifs yesterday, all done by David Whyte mostly in Processing. http://beesandbombs.tumblr.com/ All looked like fun things try in Vops/Wrangles, thought others might want to join in. Picked this one to start with, attached is my attempt with a point wrangle ( H15 ). http://beesandbombs.tumblr.com/post/107347223679/columns bees_and_bombs_columns.hipnc
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