Dave Rindner

Dave_ah

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Building Mantra shade networks. Dec. 6, 2019, 6:22 a.m.

So a simple issue. Feeding multiple texture maps into Mantra Classic and Principle Shaders. By multiple maps, I mean take two or more color texture maps, or 2D patterns, combine them using VEX Combine then piping the result into base color of either Classic or Principle shader. THe work takes place in Materials context. Problem is that at times the color maps simply don't show up, all are .rat files, or material shades pure black, and always the resulting materials, while shading is absent, from Oc AOV.
Process;
In Materials context create a Material Builder shader, and dive right in.
Inside Material Builder drop down a Classic Shader Core.
Drop two texture nodes pointing to .rat files
Combine using Mix VOP
Pipe Blend out of Mix VOP node into diff_clr of Classic Shader Core
Out of Classic Shader Core pipe layer, F, Of, and Ce into Compute Lighting VOP.
Out of Compute Lighting VOP, pipe Cf, out_Of, and out_F into Surface Output Cf, Of, and F inputs respectively.
Pipe Shader out of Surface Output into output_collect node's shader1 slot.

displacement output is piped into shader2 of output_collector,and appears to work fine.

Material is assigned in Geometry context MaterialSOP to poly geo
Problem is that the material does not appear in Oc AOV.
Oc AOV is defined in mantraROP/images/extra images planes/Oc by adding Occlusion AOV.

Houdini freezes whole pc and then Blue screen ! April 13, 2019, 5:05 p.m.

If you have Nvidia GPU and on-board Intel Graphics, disable on-board through BIOS. Be carefull! RTFM the mainboard manual, or find it online.

In Houdini DOP solver, disable ‘Use OpenCL’.

BSD is hardware issue. Also These game boards are not really trustworthy in professional apps like Houdini, Maya, and Realflow. GTX 1050 is on the lower end scale. I use Quadro P4000 and no problems, unless Houdini runs out of GPU memory, then sim either goes black, or slows down. But no BSD, knock on wood.
GTX is faster then Quadro in games and AR using DX11/12. But introduces potential problems in OpenGL apps like Maya, and Houdini.
GPU renderers like Redshift and Octane, seem to work just fine in either.
Nvidia drivers artificially turn capabilities ON/OFF depending on whether the board is Quadro or GTX. They do this for market differentiation.

Whitewater and foam shading April 13, 2019, 4:25 p.m.

The ‘Swiss Cheesing’ byProduct is bane of liquid sim VFX artists. In Houdini FLIP object and FLIP Solver there is a option of RESEED particles. Like DOSXX most interesting man, I don't always use it, but I do when I need to. Re-seeding particles , FLIP solver tries to see a problem voxel volume where there not enough particles for smooth surfacing (later used by ParticleFluid SOP for mesh gen)and fills it with new particles and/or redistribution of existing particles in a the sim. Conversely it also tries to fix voxels where there too many particles. How it does is a bit of a mystery to me. But it does work, mostly, mostly. FLIP is ‘implied’ particle position , as FLIP does not strictly enforce ‘divergence’ , which is strictly enforced in SPH liquids. In SPH, a divergence violation crashes the sim. Unfortunately re-seeding introduces either positional jitter and ParticleID attr change. Later in process, if using particles as points for rendering point clouds and for instancing, the result can show noise motion blur artifact, or random popping of instanced geometry . Now, this is what I think is happening. It may be something else. Back in my Realflow days, I dealt with this issue by either upping the resolution, thus sim-time, meshing time and render time. Later by using RF Particle Sheeter (gigity) plug-in. In RF this was mainly in RF's SPH solvers , which I consider superior to Houdini's SPH solver, but mine is a biased opinion, as Realflow was a significant part of my professional life.
There is a sort of ROT I use in FLIPs to avoid swiss cheese and positional jitter. Keep the sim moving. Don't allow any part of the simulation to slow down , where jitter and popping are most apparent. FLIPs are amazing for those dramatic , dynamic shots, where volume and chaos hide any simulation and surfacing artifacts. But I consider FLIPs not to be optimal for slow liquid motion. Like stagnant water. I notice that problems that occur at low res, previz quality or WIP sims, just go away as sim rez is increased to production weights, or when a sim motion speed is helped along with some FORCE fields with object masks to contain their effect.

https://www.youtube.com/watch?v=ypsxzVJy_9M [www.youtube.com]

The surface mesh, prior to rendering, of my Houdini FLIP sim of boiling churning water. Scrub though, FxF, and you cain see the beginning of mesh surface jitter. But the artifact is contained by having liquid moving.