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Hi, found a great link to ressources for graphic papers... http://kesen.realtimerendering.com/ ...maybe you already know it, maybe not ;-)

We have just released a new volume to our Houdini Jumpstart Series from Adam Swaab Intro To VOPS Houdini VOPS is a powerful multi-threaded environment for building tools and components of tools in Houdini. This tutorial goes through the ins and outs of VOPS, going through many short examples to get you ready to harness the full power of VOPS. We also do a quick intro to pure coding in vex, as vex is the underlying language of VOPS. In the final chapter, we show how to create our version of a polygon effector, similar to one you may see in Cinema 4D. If you are not familiar with this fantastic series then you can see all the titles HERE. Thank you Tim

divide with remove shared edge ?

We prefer pre-simming big spectacle event type sequences for games for a few reasons: 1. It's far less performance intensive than real-time physics simulations (ie: havok or apex) 2. You have total control over the motion and more importantly the end-state. You don't want a chunk of debris blocking player progression or a giant block of concrete jittering on top of a non-reactive car. 3. Pre-simmed looks way better with much detailed motion which is no surprise when comparing a sophisticated solver (Houdini for example) on a fast PC simming for 30 seconds per frame versus a highly optimized solver running on console (similar to low-end PC) simming at 4 milliseconds per frame (typical portion of overall 33 millisecond budget per frame for FX) For rigid body sims, we import them into game as simple .FBX skeletal animation assets with simple binding (1 joint per chunk plus root joint). For soft bodies, we export alembic out of Houdini to Maya, then use some custom tools to export the alembic as a series of blend shapes which we blend through in sequence to create the illusion of smooth deformation. The previous poster is absolutely right that alembic (1 shape per frame of animation, 30 shapes per second) is untenable (tooooo heavy) so we allow artists to specify the desired "frame rate" such as 6 shapes per second, etc. which provides good fidelity at a reasonable performance cost. We also try to be mindful of polycount on the these assets because they add up once you have 40 shapes (6 or so seconds of animation) to make a single large sequence. Hope that's helpful. Best, Ewan

This is a gotcha that's gotten me a few times. In the copy sop, you need to go to the Attributes tab and check "Use Template Point Attributes" which passes your height attribute through to you attribute VOP where you have effectively mapped it to your color ramp. I also brought your "height" attribute into the attribute VOP with a param node. Cheers, Ewan bank5_airship.hipnc

All right, let's find my Vancouver Houdini User Group (VHUG file for #6... It was a quick "masterclass" on collisions, there's a RBD section where's I'm convexifying a character in different ways as an example. It may not be as useful without me explaining what's going on but, well, here it is. vhug2_v003.hipnc

you need to make sure your constraints are in rest pose of the packed pieces, not in their copied positions look at the file, added nodes are green I as well checked Solve on Creation Frame on your rbdpackedobject1 as the first piece was not added due to that (since it's being created on 1st frame) multpleConstraint_v01_fix.hip

maybe this one obj_ID.hip

just create export parameter in your shader with name you like for example object_id (and add it to image planes in mantra) then in each of your object create attribute called the same with the same type and assign different value per object what works best is to create Vector4 attribute since then you can have 4 different object groups (red, green, blue, alpha) so {1,0,0,0}, {0,1,0,0}, etc in that case you'll get perfect antialiasing between them as you can separate it per channel in comp to create more object groups just add another variable export like object_id2 etc you can of course export just float variable and assign values like 0, 1, 2, ..., but that will create problems in antialiasing where any 2 non neighbour ids overlap (like 0 and 3, since interpolated value will go through 1 and 2)

Ahh... The volumeslice... Thanks everyone!

Glad you found an answer. Depending on your setup, you possibly could also use the "Pump From Object" shelf tool. This tool uses a FluidSource SOP to create a velocity field from geometry point velocities, then a SourceVolume DOP to bring those velocities into the FLIP simulation, giving you a fair bit of control. Attached is an example of using a simple POP net to transfer particles velocities to a FLIP tank, all set up with shelf tools. A similar setup should work with Pyro sims as well. pump_from_particles.hip

Isooffsets are wonderful things! Perhaps my favorite Houdini bit! If you generate an sdf you can quickly find out how far something is from a surface, so you can shrink or grow things, see if other geometry bits are inside or outside another geometry, create stable and robust collision objects. With volumes you can also store scalar or vector fields, both of them useful in simulations. One of the biggest benefits of volumes is that they are a robust way to pass around data, and it doesn't have to be hires (for example you can pass velocity vector fields to particles pops and get away with comparatively low resolutions)

They provide you with ways to generate volumes. Either directly as a block of volume (volume sop) or by calculating a volume from a mesh, a pointcloud, another volume with different algorithms to compute the volume (iso-offset). The isooffset can also create a surface mesh out of an incoming volume. Volume are very useful tools for modeling, or scattering points in the volume or feeding it into sources for fluids. You should do a search on this forum for "volume sample from file" or "volume gradient from file" to see some of the things volumes and sdf are used for. You might want to search for "signed distance field" (sdf) too - as that is often more useful than a plain volume.

You didn't set your isooffset to output a fog volume. And your VOP network was kind of odd, so I changed it around. fog_test_edited.hipnc

For fog you have a few options. Copy metaballs to particles and apply a billowy smoke shader - check metaballs as volumes under your geometry nodes render tab Same deal as above but use i3dgen to create a 3d texture. Look in the docs. Create a rough shape that you want the fog to be in, then use an isooffset to create a fog volume. Modify the volume with some 4d curl noise(using time as the 4th value in the vector4) in a volume VOP. Simulate smoke in DOPs On top of all of this you can apply displacement to volumes to get more detail. There is plenty of help on all of these if you use the search bar. Jason