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StepbyStepVFX last won the day on October 8 2018

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    VFX, Computer Graphics, AI, Deep Learning, Cinema and many more...
  1. Earthquake in Paris

    Some new finished work ! Been working a long time on this one. Not totally finished yet, there may be some cleaning to work on... Any feedback is welcome.
  2. Jumps in opacity / density of volumes at rendertime

    Found that using Raytracing instead of Micropolygon rendering was giving cleaner results, as well as increasing the Volume step rate (volume quality)
  3. Hi All, I am rendering a simulation of smoke and it seems I got some "flickering" or "jumps" in the opacity values of my smoke. It is obvious between frames 181 and 182, where the smoke dissipate a lot in some areas, then revert to previous values some frames later, between 184 and 185. And again between 188-189 and 189-190. I am using the Pyroshader (without noise, without emission, only smoke, nothing fancy... no remapping of value, really straigth out of the bos shader). Nothing fancy neither in Mantra : volume limits up to 1, and opacity limit to 0.995, normal value). Did this already happened to someone ? If yes, any thoughts on how overcome that problem ?
  4. Venom!

    Here are the first videos from AMcKay, with nice assets to download for free (among them an animated Venom model abc format). The video shows a Thinking Particles / 3DSMax pipeline, but this can easily be applied to Houdini, so the tutorials are relevant for the process of creating those FX (particles emmissions based on procedural textures, law of physics applied to particles, meshing to get tendrils and so on... nothing that can’t be done with Houdini, of course, but nice workflow to learn). You can ask to be on the mailing list to receive the last videos when they will be released (in few days), that’s free. The links will remain until 4th or 5th december : http://allanmckay.acemlna.com/lt.php?s=9e10255f483501641a71a44c1245cd19&i=752A912A2A12328 http://allanmckay.acemlna.com/lt.php?s=9e10255f483501641a71a44c1245cd19&i=755A930A2A12341 http://allanmckay.acemlna.com/lt.php?s=9e10255f483501641a71a44c1245cd19&i=761A937A2A12361 http://allanmckay.acemlna.com/lt.php?s=9e10255f483501641a71a44c1245cd19&i=775A1161A2A12416
  5. Crowd Training Sources

    Flying crowds... you mean flocks ? https://cmivfx.com/houdini-flocking-systems
  6. WIP - Ghost crabe waking up in the sand - Grain Solver

    Update of the ghost crab. I still have to render the last 2 seconds of the shot - 5 days calculations because my computer makes too much noise at night... https://vimeo.com/287781060
  7. Hi, just to share a first pass of a black hole that has the look of "Gargantua", seen in Interstellar. Still lots of work to do on the accretion disk (for now, as it is a proof of concept, I just used a cloud :-), and the background as well. I will have to light the scene better, so that we see the little planet orbiting around...
  8. Move points through the "center" of a SDF

    Just to complete a bit, once you have the gradient of the SDF (using a first VDB analysis set on gradient), calculate the curl of the gradient : this should give you the vector field that goes along with the flow. That being said, this vector may be infinite at the center of the VDB... so maybe normalize the curl vector field using a new VDB analysis. My maths on curl calculation in cylindrical coordinates are a bit rusty, but with vectors that are Vtheta = constant, Vrad = constant and Vz=0; the curl should be oriented only in z with Curl.z = constant/radius... whcih goes toward infinity when radius goes to 0.
  9. Move points through the "center" of a SDF

    Hi, I just throw some ideas, maybe it is redudant with what Mangi posted (can't open the file being at work) : - initial setting of particles : I would create a thin box that intersect with your SDF pipes (vdb combine), then scatter a lot of points within this intersection (thousands, let's say), and then use the Cluster points, with output set on Average Points, and the number of clusters set on the number of SDF pipes you have. That should do the trick. - advect the particles along the SDF pipes : you can indeed try to use a POP Curve. Maybe you can also build a VDB with a velocity based on the SDF : the gradient of the SDF should give you a vector field that goes toward the surface, and from there you can build a new vector field perpendicular to this one, that will follow the "flow". From there you advect the particles using this vector field (VDB Advect POints, inside a SOP Solver).
  10. Assemble deletes UV attribute ?

    If you have asked the Assemble sop to output packed geometry, you won’t see the UV unless you unpack the geometry. These attributes are not lost, they are kept at the geomtry level of the packed primitive. In essence, a packed geo allows to you to manipulate « lighter » object : they are considered just a point and the geo is stored elswhere. It allows instancing and light management of scene, the geometry being only accessed at render time. http://www.sidefx.com/docs/houdini/model/packed.html
  11. Sandstorm with Billowy Smoke ?

    Hi, Have a look at these topics : Hope that helps ! :-)
  12. findattribval in for loop

    No, the findattribval of 16 and 16.5 returns integers, and not arrays therefore the for loop cannot work properly (it does not know on what to iterate). If you want to learn to learn VEX on Houdini version 16 and/or 16.5, refer to the docs of those versions, do not use the docs of H17 :-)

    You mean stopping them once their speed reach a certain threshold ?

    Hi, You can either use a POP Wrangle or a POP VOP, and play with the speed directly within your sim (and even group the particles you want to slow and Wrangle only this group), and keyframe a factor you would apply of the speed (or a ramp). Or you can also tweak your sim afterward, using CHOPS, which also gives you lots of control.
  15. findattribval in for loop

    Hi, Which version of Houdini are you running ? Seems from the doc that H17 allows findattribval to return an array, but from my doc in H16 or H16.5, the signature of that vex fiunction is only int. So in my opinion, your Wrangle is getting an error because your for loop needs to iterate over an array, while you are feeding it with an integer... In this case, I would recommend to work with findattribvalcount and then iterate with findattribval(0,"point","id",10, count). See their 3rd example :-)