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thanks ! i'm looking for noncommercial, free, libre, things. although I'm dreaming of a Houdini that can just automagically distribute the cooking and caching of any node on a graph on all the seflannounced, selfdiscovered CPUs/GPUs/ETC on a network. But I think it would have to be rewritten from the ground up for this to work. i'll be posting some more thoughts on this on this forum in the coming weeks I hope I can get your feedback then. talk to you soon !

hi marty! thanks for the link. i was wondering if you would know of something that would help combine that TBB kind of approach with distributed computing: heterogeneous-distributed computing. i am looking for something that would pool the compute units on a node AND the nodes on a network (without having to think of the whole thing myself). i'm dreaming of a BOINC+TBB lovechild of some kind… already implemented and open source thanks in advance for any pointer you (or anybody else) might have

Yes! I will look into it soon! Thanks for pointing it out! V

Also, I just want to say a word or two on the test scene I'm building for this. It contains: an array of diffuse color spheres arranged according to the macbeth chart a mirror/chrome ball an array SESI shader balls for each non-human skin measurement preset an HDRI map environnement light (one of the Dosh images that is included in the Houdini distribution perhaps) checkerboard cyclo background (anyone kind enough to suggest pattern ideas? i'm hesitating on this) a full scale full-body human figure. I tried the MakeHuman one but it looks like crap. The Danylon geo is head only and I don't want it floating in the middle of the scene with eyes closed, it freaks me out (one of the objective for me is to shade it in a way it doesn't look dead ghoulish and I think full-body with eyes open is the way to go). I have some that don't look like crap but I cannot share them. Is there anybody that knows of a good free full scale full-body human figure that we could use here? preferably a scan, preferably male because: in-texture hair don't look so ugly on guys and I don't have time to create the full hair geo and even then, male hair geo is easier to do you only have the genitals to hide (behind a realistic short/speedo or whatever, it's easier than going with the full multi piece bikini/lingerie kit) culturally, photorealistic female is not photorealistic (and let's not get started on this) That's it for now. Thanks.

Hi Dennis. Thanks for pointing this out. Do you know, for instance, what is the name of SESI's GGX eval so I can use it with cvex_bsdf alongside my own sampling function and more importantly look at the eval code to see if it diverges (when and how much) and also get inspiration to build my own if necessary? Thanks.

I still want to give myself 2 weeks to cover Fs properly before restricting anything, but as I'm writing this, I see no reasons for not going with SESI's implementations except for 2 things : incorporation of measured reflectance as presets and human skin (for every other case of generic SSS, mantra surface is good enough). Speaking of human skin, I got a reply from the Activision guy saying that adapting the provided code to the ideas in the latest article is feasible. So I will look into that. So my question remain: is it possible/efficient to use only the importance evaluation functions of SESI's reference Fs with custom sampling functions to use measured reflectances and other sampling methods (for human skin, for instance)? I'm not even 100% certain my question makes sense.

Hello eetu! I'm glad that you came by to spill some wisdom beans! ;-) So you wrote realtime-inspired cvex_bsdf and you didn't tell anybody? Naughty. What do you mean by inefficient? Writing eval functions is hard? I'm asking because one of the reason why I said I'd rather stick with the SESI implementations is that I could not find anything about importance evaluation (and a sh**load about sampling). BUT as Emmanuel said, and I agree, it is also because the importance evaluation functions are blackboxes (more so than the sampling functions, or maybe I overlooked something?) that we should write our own(s?) if you know what I mean. Is it possible (and I know I'm stretching) to use SESI's evaluation functions (how to call them, then?) independently with our own sampling functions? Just my shitty theory that (as per your signature) is better than no (publicly available) theory at all. And since you asked, I shall insist: SESI GGX ~= Jim's GGX? If so what are the modifications and why? In the sampling function itself or in the eval? And since you are here (bis), tell me please on a scale of 1 to 10 how crazy this sounds: dump all the reflectance measurements I can find into a VEX header in some kind with a standardized static data structure (with the new H14 VEX array manipulation functions AND CVEX support for array binding, arrays are sexy again) and use them as the basis for presets (I looooooove presets) or, even better as material parameters. I'm going for a walk to calm down now lol.

Browsing on the Activision guy's website, I found this. I contacted him to know more about the paper and its open source implementation. Will look into AxisAnimation later and maybe contact them too. Thanks, mantragora.

Re: skin, human character shading is the ultimate test for a shader I think. I test mine on clothing, props, eyes, nails, hair and skin. I have never been satisfied (æsthetically) with generic articulations of SSS for human skin and I have seen that most treat human skin as a special case. I'd still want to include it in this shader because ideally for me it should be able to handle all the surfaces in the scene. MERL has a measured reflectance database only for human skin, Arnold has a shader dedicated to human skin, Dany made a PBR shader for human skin separate from his general PBR one. So: I would like our shader to be able to shade state of the art human skin and I think the best way is to address it specifically. I will include human skin models in my 2-week study of Fs and reflectance measurements. I am really surprised nobody has yet said anything on shading human skin over at Wikihuman (formerly known as The Digital Human League). But I will use the same strategy: look at both the GPU/RT and the unbiased strategies and frankenstein one up.

Hi, I give myself one or 2 weeks to investigate custom CVEX vs SESI VEX Fs. I will report here. But I agree with you on all principles. Just in case, I asked the UE shader author if there is any update on his article. I have 2 more questions for you: how to you plan to incorporate general SSS / human skin shading in all of this if ever? will you look at measured Fs (MERL, Marmoset & al)? because I really like the idea of measured presets as a starting point.

Thanks for contacting Dany. It had to be done, I think. I would like to investigate SESI's Fs and especially GGX more thoroughly before going with custom CVEX. What do you think? Re: UE4: me too. Actually, I want to know if it is better to use the Unreal Editor with the Houdini Engine with their shader or port it to Houdini and work in Houdini natively. What is your take on that? I mean for previz and all, not just for making real-time versions of assets for games. Also, do you have a deadline right now for this? What is your time frame? Take care!

@pezetko: I see a (VERY crude) viewport shader implementation, but is there a Mantra one as well? and will they be configurable because nobody uses the GLSL shaders bundled in the Algorithmic products (they dont support a fraction of what the Substance engine offers), for example as of a couple of weeks ago, I still had to implement opacity myself… there is no refraction, no sss emulation, etc. @sebkaine : the other nice thing about VEX is that you don't need a license to open it ;-) can you post your thing in an Apprentice HIP, please ;-) also, are you talking about Dany's 2 PBR shaders on Orbolt : the "skin" one and the MERL PBR Layered one? I have purchased both of them, the code is in the OTL, but I think we should involve him or at least ask for his permission before repackaging his thing. Otherwise, I agree that Jim and Dany's shaders. I have no experience with Roman's PhyShader, but is there a reason why you are discarding his work? I'm just saying this because his code is available on Github whereas neither Jim nor Dany have open sourced theirs. And also, I think the reason why Jim wrote his F in CVEX is that GGX was not implemented in VEX at the time. I think that unless you have a good reason to discard SESI's GGX implementation, maybe we should stick with it (it's the default specular "mode" in the mantra surface shader now).

lol this is so cruel! y u do tis evritime, houdini. ;-) i was working on understanding the fur system and scripting my own crowd system and then came H14. I know that they are working on shading and texturing this time, but what should I do now, hibernate until then H14.5/H15? Anyways, reading and researching is never lost. Anyways... Back to you Emmanuel… First, regarding CVEX, I'm not knowledgeable enough to know if it is really an alternative to writing VEX shaders. So, right now, I stick to VEX. Also, not bothering with Reyes/Raytracing/Micropolygons anymore and sticking with PBR. Secondly, I think we are very aligned on the GLSL/VEX thing (aka Viewport/Mantra aka Realtime/Unbiased until they merge for good). And I think standardizing the shader interface (its parameters, which parameters can be maps, etc.) will come before standardizing the shaders themselves. Just everybody is pushing in this direction and the two big trends I see are 1) measured reflectances/brdf and 2) human skin is approached separately from everything else in the (then not so-) universal shading architecture. And really if we should wait for H14.5 maybe more details are in order, no?

+1 for GLSL/Viewport vs VEX/Mantra parallel shading love (UDIM, PBR, etc.) I don't know how it could be done elegantly (VEX to GLSL/OpenCL LLVM compiling, perhaps?).

Salut Emmanuel, I posted something related a couple of weeks ago here. I figured since I've got zeeerooo answer that writing one's universal shader was some kind of mandatory arcane initiatic rite one has to go through. And I kind of understand and respect that "go alone in the woods" attitude now. I'm still alone in the woods, I might not survive, but I had to answer myself some of the questions you asked. The answer I have for myself right now is this: I eliminated totally VOP+Inline except for prototyping and then I look at the generated VEX code and I clean it and incorporate it in the my main text-only code. Maintaining code allows using better text editors than the Houdini interface and versioning systems such as GIT/Subversion/CVS. I am still hesitating between writing it in plain c and then calling it via CVEX or direction using VEX. CVEX is appealing because Arnold shaders are written in C/C++ and you could thus share the same code base. But I tend towards VEX because I can rely on Houdini's optimization and using code snippets for modelling and simulation (not only for shading). As a side note, I don't know about RIS: does it use RSL? I think I saw it was C/C++ but I'm not sure. If it is the case, then it's a +1 for CVEX (I guess). I have the feeling that a lot of people/studios are working on universal PBR shader architectures right now. It is moving fast. Especially with the game/vr/realtime industry now catching on on PBR. I decided to do my own research now only to be able to understand what is going on and be prepared to incorporate ideas from other efforts as they are published/shared. If I can contribute an idea or two eventually, it'd be great. But there are some seriously involved intellectual/monetary forces that I simply cannot match. I just hope they share the love eventually. So there you go. Hope it helps a little. Vincent