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Everything posted by Sean-R

  1. Natural Randomness Ratio and Scale Ramp

    FIrst of create a random number between 0-1, you can use the @ptnum or @id (if you have one) attribute, you can then reference this random number in a ramp expression. The code would look like this: float rand = rand(@ptnum); v@scale = chramp("Scale", rand); You can then hit the spare parameter toggle next to the vex expression and adjust the ramp curve to how you want it. Bear in mind this will distribute the scale of the debris to between 0-1 so if you want them to be a different scale to this you would need to fit the scale value after the ramp expression.
  2. Check out this video by Matt Ebb. He has something similar to what you're after halfway through (but it's definitely worth watching the whole thing)
  3. Is it a Packed Primitive? You could use a point expression on the camera transforms at object level
  4. centered Point per Primitive

    This code should work in a Primitive Wrangle: // Adds a point at the position of each prim addpoint(0, @P); // Remove primitive and all points connected to it removeprim(0, @primnum, 1);
  5. You can control the density of scattered points by an attribute, the scatter SOP defaults to a "density" attribute but you can use whatever you like. For the distribution that you have in your top image you could make a black to white gradient on a grid then replace "density" with "Cd" in the Density Attribute parameter.
  6. Access numpt at input 2 of wrangle

    Hmm, not sure. Maybe because it's a different type of attribute and opinput can only access what's visible in the Geometry Spreadsheet?
  7. Access numpt at input 2 of wrangle

    You can use the npoints vex expression, so: npoints(1)
  8. basic questions- question 1

    There are a bunch of visualizer buttons on the right hand side of the viewport. One of them displays the primitive number.
  9. basic questions- question 1

    Hey! There are (at least) two ways: 1. You can type in the primitive numbers into the Group parameter at the top of the transform node. 2. Once you've made your selection you can hit "E", "R" or "T" to create and Edit node. The hotkeys are for Scale, Rotation and Translate respectively. Hope this helps
  10. transfer Cd to vdb from particles

    I can't look at your file, but you can plug the original geometry (with colour) into the second input of the convertvdb node then check "Transfer Surface Attributes". Hope this helps!
  11. Ray node scale input

    It should work if you write @Cd into the Scale parameter.
  12. Spotlight instancing on deforming geo

    Yup, The instance SOP at the /obj level should do the trick!
  13. Have you checked out the houdini help? http://www.sidefx.com/docs/houdini/shade/textures.html The principled shader has parameters to attach texture maps.
  14. FLIP fluid particles growth?

    Hey! So, I realised that as it's on a single frame you don't need to set an id attribute and Ben's set up will work with a fluid sim. I've attached an example frozenFluid.hipnc
  15. pscale in stream

    Not sure why that doesn't work in the dopnet, but the streams are accessible as groups so you can set the pscale at the SOP level. EDIT: Just checked again and I can set the pscales of separate streams using either the POP wrangle or POP Proximity in a popnet. How are you setting the pscale?
  16. FLIP fluid particles growth?

    Should be possible. You would have to add an id attribute to the fluid though, which can be enabled in the flip solver under the Particle Motion --> Behavior tab
  17. Why does this simple line errors out?

    Yup, what Noobini said. Try: vector pp = set( random(10), random(10), random(10) );
  18. Sticky FLIP on moving Object

    There are a couple of VEX functions you can use to help stick particles to an object, volumesample() and volumegradient(). You will have to convert your cherry geometry into a vdb to make it work. Multiplying the returned values together (and negating the volumegradient) and adding the result back onto the particle position. The code should be put in a POP wrangle and looks like this: @vs = volumesample(1, 0, @P); v@vg = volumegradient(1, 0, @P); @P += @vs * -@vg; The "1" means to look at the POP wrangles second input, which I've set to the cherries vdb. The "0" means it's looking at the first primitive of that input. @P is the current position of the particle This should work with both pops and flip. I've attached a hip file trying to recreate that gif you linked. the above setup can be found in the DRIP_SIM section cherries_colliding.hipnc
  19. @Atom - Ah yeah you're right. I've attached a file with the point deform in the correct place to get your group to work with your new geo groupOnRemeshedGeo.hipnc
  20. You can use a timeshift set to the frame you set the group on and then use a point deform against the deforming mesh to get your point consistency back. How have you prepared the mesh? It would be better to go back and fix the swimming there.
  21. How to create curves from particle fluid?

    I'm not sure what you mean. That was straight from the sim, do you mean the points from the trail?
  22. Patronus Charm Effect

    You can control the glow and fade away in a shader. The prinicipal shader has an emitint and an opacity scale parameter which you can drive attribute, like age.
  23. How to create curves from particle fluid?

    Here's one way, I could get quite heavy though. I checked "Add ID attribute" in the flipsolver node, connected a trail to the flip particles and chose how long I wanted the stream to be. Then I dropped down an add node, set it to group by attribute and set it to ID
  24. Explosion effect with particles

    Bit late to the party but thought I'd throw together a quick and dirty setup. Scatter some points on a sphere. "Group" together areas of points using the cluster sop. Colour the points using the cluster attribute created in step 2. Set up initial velocites in a pointvop, randomised with a noise. Sim with some variation added to the initial velocities to break up the shape. Emission is only on for the first frame. Trail the sim to a frame that you're happy with in regards to explosion size. Use a point replicate to bump up the number of particles* Use a VDB from particles node to create a density and Cd volume. * I wanted more control over the pop replicate node so I added a UV attribute which then drives the uniformscale parameter. It needs a fair bit of tweaking to get to that top picture but should get you off to a good start! particleExplosion.hipnc
  25. Bullet Going Through a Mechanical Heart

    I would just animate the bullet and treat it as a collision object. If you absolutely have to sim the bullet then I would treat it as two sims, one with just the bullet, then with the bullet as a collision object for the heart.