Skip to main content

Growing Objects

I saw this post over at odforce and have been playing with growing objects in a dynamic way ...



It is basically just points scattered in the volume of an object, then a SOP solver is used to increase a points pscale if it is colliding with another point. Metaballs are copied onto the points, converted to polys, then cookied with the original geo (not in the video above though...)

This is the source geo and with the scattered points:




Some attributes are added for the sim:



The pscale attribute is set to 0 except for one which is set to maxSize to start the sim going. Roughness starts at 1 and decays when a point has stopped growing, this later is fed into the shader to increase the cone angle on the reflections and refractions...

These points get loaded into a DOP network and then into this SOP solver:



The pointCloudSop is a little VEX script that tests for collisions between points:

#pragma hint filename oppath
#pragma hint pscale hidden
#pragma hint maxSize hidden
sop
pointCloudSop(string filename="/obj/geo1/PC";
float pscale = 1;
float radius = 1;
float maxSize = 1;)
{
if ( pscale <>
{
string file = concat("op:", filename);

float isColliding = 0;

int numpoints = npoints(0)+10;

int pointcloud = pcopen(file, "P", P, radius, numpoints);

while(pciterate(pointcloud))
{
float dist;
float otherPscale;

pcimport(pointcloud, "point.distance", dist);
pcimport(pointcloud, "pscale", otherPscale);

if ((pscale + otherPscale) > dist) isColliding += 1;

}

addattribute("isColliding",isColliding);
}

}

vopsop1 adds growRate to pscale if it is colliding, vopsop2 just maintains roughness if the point is growing and decays it otherwise.

After that, the rest of the SOP network just copies metaballs onto the points. I was using the cookie SOP to get the intersection between the original mesh and the metaballs but the cookie sop was a bit unreliable :/

hipnc file is here

Comments

  1. Hi, I've tried to open your hip in houdini11, seems borken, I really interested to see how it's working... could you updated it if you have time? Thanks.

    ReplyDelete
  2. should be a h11 scene but I will update it when I have a sec!

    ReplyDelete
  3. took me a while! swapped out the VEX node for a VOPs one.

    Could be optimised but it works ...

    http://users.on.net/~tmsmsa/PC_grow.hipnc

    ReplyDelete
  4. Hey man, can you make it work for H13, please? There's few things different, attributecreate is now 2.0 and it doesn't seem to take your expression ch("../attribcreate_maxSize/value1")*2 on convertmeta. Few other things are wrong as well, sometimes after the dopimport, the delete node will create a small cluster in the middle, but sometimes will not, and regardless the cluster is not growing as it supposed to. :(

    ReplyDelete
  5. I will check it out, there is probably a much better way of doing this now!

    ReplyDelete
  6. very cool effect.
    I like your work man! thank you.
    is there any chance to do it in H 15 ?

    ReplyDelete

Post a Comment

Popular posts from this blog

Cloth tear geometry and shading detail

Been adding geo detail to the torn cloth and shading the additional geo. Shading sure is fun! :) Thickness added to the cloth geo Extrude sides are extruded out again  The second extrusion is done twice, once for the U direction, and once for the V direction. Polyframe is used to get the UV gradient to extrude along, vopsops are used to move the extrudeFront points after extrusion as you can't control the extrusion per point with just a polyExtrude node... The extrusion is done twice so that the two different surfaces represent the opposing thread directions. since my geometry (and therefore tears) are in line with the U and V direction, the effect is not obvious in this case. The extra geo after shading The .hip file below has a slightly newer shader than in the video and the image above, I removed the part of the shader that created the soft ramp for the alpha edge and used just the thread noise instead; it now looks more like: Slightly newer shader than

Wire solver and wire deformer.

Just playing around with the wire solver and deforming wires onto wires... rendered as tube primitives, 2 area lights and an env light, took about an hour to render 2K :/ hipnc is here

Worm locomotion with FEM

I have always wanted to do a dynamic locomotion setup, I have tried in the past with wire and sop solver with .... interesting results ;) With FEM in Houdini 13, the rest attribute is stored on vertices which allows a tetra to change its rest state independently of the surrounding tetras. With this, parts can be expanded and shrunk to get a muscle type action. I have started with a worm since it is quite simple, the contractions and expansions move back along the worm in a wave, opposing the travel direction. It took quite a bit of tweaking to get him moving at all. One major element of a real worm's action that's missing is the little hairs that grip the ground. I couldn't find a way to change the friction per point so I have gone a bit hacky and multed down v wherever I didn't want the worm to move. I would love to hear if there is a per point friction control! Here is the video Houdini 13 FEM Worm locomotion from Sam Hancock on Vimeo . ...and the .hip is