Forgot your password? As an example. In your network create a vopsop below a popnet. Inside the vopsop connect the point ID attribute output of the globals into a random vex node. Next connect the output of the random to a ramp parameter vex node. Change the ramp type to Spline Ramp float. Next connect the parameter output of the ramp vex node to a fit range vex node input value.
Set the destination min parm of the fit range node to 0 and the destination max parm to 1. Finally connect the shifted value output into and add attribute vex node. Place pscale in the attribute and local variable name parms.
Finally at sop level connect the output of your vopsop into the template to copy to side of a copy node and some other geo in the primitves to copy to input of the copy node. Adjust the spline ramp on your vopsop to see the results of pscale.
There is only 1 in 2. I think you have a little too much time on your hands You need to be a member in order to leave a comment. Sign up for a new account in our community. It's easy! Already have an account?
Sign in here. Existing user? Sign in anonymously. Recommended Posts. Posted February 2, Share this post Link to post Share on other sites. Give a pscale attribute to a point and copy stamp something: it will scale accordingly. Render a point as point and pscale will determine its size. Posted February 3, Houdini allows you to build rigid body constraints with polylines.
The lines represent the constraints, and the ends are attached to the rigid body objects by name matching. If no name matches, then they get attached to the world. Constraint networks can be built with 'connect adjacent pieces' and a few wrangles, but more interesting results can be had by procedurally modelling the constraint edges, offsetting the constraint ends, and mixing multiple constraint types.
From skimming the docs and looking at other peoples setups, here's what we need to do. In the above diagram the packed rbd objects are blue, the constraint polylines are green, and the points of the polylines are red:.
The above gif shows how I've built constraint networks thus far. How does it sim? Oh, the prims need a restlength attribute. Without it the constraints assume they should be of 0 length.
Inserting a 'convert line' sop before the prim wrangle will add a restlength for us. Now when we sim, we get this:. Nothing happens.
The constraint lengths are maintained, there's no other forces in the scene, so it all looks motionless. Good, but boring. Lets add some gravity. If you look at the prim wrangle, and inspect the geo spreadsheet in points mode, you can see that the points have a name attribute, which matches to the names of the packed geo. That's how the constraint network knows how to connect things; it matches on name. If name is an empty string, that constraint becomes pinned to the world.
Let's see what happens:. Sure enough that constraint is pinned, and the chain swings around that point. Unfortunately the first cube falls to the abyss. Well, now none of the points have a name that is 'piece0', therefore its an unconstrained object, and falls to its death.
How to fix? NOTE: In In A lot of earlier setups mine included would use a name like 'world', these setups will need to be updated! This is what we wanna build; a new little mini line near the first box, one end has name of 'piece0' so its pinned to that box, the other has an empty name so its pinned to the world. Coming up with a clean procedural way to do this isn't as intuitive as I'd expect.
HOUDINI VEX SNIPPETS
Lets have another look at the setup so far; polylines between the objects, an extra little one for the first object pinned to the world, it all does its rbd constrain dance:.
These are all hard constraints. Well if they're hard, why are they rotating? Especially the first object that should be pinned to the world? The reason is the default constraint behaviour is to pin position, not rotation.
Here's what happens:. The constraints now work like rigid wires, and lock all the rotation down. Sometimes you'll want one or the other, or maybe even a combo of the two, its handy to know you can do this. Again, lets look at the sim, pay attention to how the constraints lines move in relation to the boxes:.
While the sim is working, the constraints move through the boxes like they weren't there; if anything its as if the boxes are constrained to the points, which doesn't feel quite right. Instead, compare to this setup:.Forgot your password?
By fiverobNovember 3, in General Houdini Questions. I feel I'm close, but I'm struggling with a n00b problem and was hoping someone could take a look and help me out. I have an attribute on the primitives that I want to drive the scale of the copied spheres. I've done an attribute wrangle on the primitives to create new points at the center of each which I plan to use as the locations for the copied spheres. I just can't seem to work out how to transfer the attribute AND delete the primitives.
I'm not having any luck with the attribute transfer node. And here's a link to an animated version. You need to be a member in order to leave a comment.
Sign up for a new account in our community. It's easy! Already have an account? Sign in here. Existing user? Sign in anonymously. Transfer primitive attribute to generated centroid point? By fiverobNovember 3, in General Houdini Questions houdini attribute transfer centroid.
Recommended Posts. Posted November 3, Any ideas? Thanks legends. Share this post Link to post Share on other sites. Posted November 4, edited. Posted November 4, Posted November 9, You guys are legends. Create an account or sign in to comment You need to be a member in order to leave a comment Create an account Sign up for a new account in our community.Yongji Chen prepared a little breakdown of his Ice Bunny simulation made in Houdini.
The first thing I did was adding noise on the bunny by converting the geometry to VDB object and then use Worley noise in Volume VOP to let the surface look more organic. Once I got the shape I want I generated the points from the geometry. The pscale attribute controls how fast the ice growth can be.
And we can randomize the pscale to make the growth look more realistic. I used two different types of noise in the point VOP and offset the noise by frame. I also used a volume sample in the point VOP to get the SDF value from the bunny and used a fit node to multiply that value with the pscale. So the closer the growth is getting to the surface of the bunny, the slower it is going to expand.
Add another layer of the noise to generate inner crack which can help me render out more realistic refraction of the ice. After that, I converted the VDB back to the polygon. The VDB type I used this time was density. In order to make the ice foggier, I also created a new render geometry and linked that to the volume VOP I just used for generating the inner crack.
Comments 0. You might also like.Thursday, March 26th, Article by Kevin Pinga. Follow his 10 production-proven hacks to create faster, more flexible FLIP fluid simulations. Houdini provides a robust set of tools when it comes to simulating fluids.
However, making fluids look realistic is a particularly challenging task, particularly for broadcast work. With TV shows now depending heavily on visual effects, delivery deadlines are getting tighter, yet quality expectations are comparable to those for effects seen in feature films. The pressure is on the artist to make sure a shot makes it to final before it is aired, which in most cases is only days sometimes hours!
These tips and tricks can help you manage your fluid simulations more efficiently when trying to deliver fluid shots in a timely manner, while still maintaining a high level of quality. The images in the article have been scaled down for the web, but you can download the orignals here. Sourcing fluids with POP Source provides familiar emission, activation and velocity attributes. This is what you get automatically when using the shelf tools.
Increasing the resolution of your VDB to get accurate more accurate sourcing can slow things further, before you even get to the simulation phase. This source can be read in by the POP Source node wired into the Sourcing input of the FLIP solver itself, in the same way that you would import a source for a regular particle simulation. The controls on the POP Source node are also much more intuitive.
Most artists should already be familiar with them through their time working with regular particles. Particle count can be controlled and monitored in a much more predictable way, independent of the Particle Separation of the FLIP object itself. This is why we were able to source using the POP Source node in the previous tip. The POP Force node is a staple for creating interesting motion when working with regular particles.
So why not use it with FLIP fluids too? Using it to introduce even a small amount of noise can create a more appealing-looking fluid. Low-frequency noises can also be useful for creating detail without having to increase your particle count or particle separation.
Be careful not to add too much noise, as this can cause your simulation to look unrealistic. Coupled with a POP Drag node, it works great for controlling high-velocity particles that can otherwise go out control. Referencing the parameters in Bounds qL helps to set simulation limits. The Bounds qL node is a very nifty tool that packs in many simple but useful features.This is a classic effect in Houdini.
I stumbled upon it over at Odforce. As you will see from that thread there are many elaborate ways of achieving this kind of growing curve. Hope you have fun! See this image:. As the Point Relax SOP offers an additional input for a surface to adhere to it is very straightforward to let the differential growth happen on a gven geometry. Growth on a surface. Basic Setup: Download Project File. Advanced Setup: Download Project File. Very detailed discussion about this topic on Odforce.
Thanks to giant cow films for their free HDRIs. Absolutely right — I cut it out accidentally.
Have a look at the supplied scene files, it is set up correctly there. Gonna add a note in the video description. Thanks for pointing this out! Cheers, Moritz. How does that work? Excellent tutorial I should have started by sayig that! Olivier How did you get the remesh working on a mesh object? I Achieved to make it work using the remesh, although I dont know how to affect a part of the geometry only and not the entire mesh I can not get my group to show up in my solver… maybe its not the way to do.
Hello, thanks for a wonderful tutorial. Would it be possible to restrict the growth to a shape?All the same Lynda. Plus, personalized course recommendations tailored just for you. All the same access to your Lynda learning history and certifications. Same instructors.
New platform. Learn techniques for creating custom tools to manipulate attributes in Houdini. Now we're going to build a system that helps us…scale our points over time. Are you sure you want to mark all the videos in this course as unwatched? This will not affect your course history, your reports, or your certificates of completion for this course. Type in the entry box, then click Enter to save your note.
Start My Free Month. You started this assessment previously and didn't complete it. You can pick up where you left off, or start over. Develop in-demand skills with access to thousands of expert-led courses on business, tech and creative topics. Video: Create pscale. You are now leaving Lynda. To access Lynda. Visit our help center. Motion Graphics. Preview This Course.