ChristopherC Posted October 22, 2015 Share Posted October 22, 2015 Hi there!I've been trying for weeks to reproduce the flame as shown in the video below, thinking that the main trick would be to get the sources and the pyro solver shapes to pulse really fast, but no luck so far.https://youtu.be/aCpBT3sIPc4?t=80 (from 1:20 to 1:27)The sourcing is being done from 3 overlapping circles that I've animated/deformed to get it to look like the base of the flame in the video, then I created the fuel & temperature volumes with loads of animated noises, created a separate pulsative CHOP animation for the disturbance, shredding, and turbulence, and I've tirelessly played with all the settings from the pyro solver and the source volume. Not sure what to try next.Any tip to achieve this kind of look?Cheers! Quote Link to comment Share on other sites More sharing options...
ChristopherC Posted November 2, 2015 Author Share Posted November 2, 2015 (edited) In the end this is what I got after more tweaking: On some frames the reference fire has some interesting shapes that I didn't manage to reproduce, and I'm not too happy about the frenetic pulse at the base of the flames, but it's time for me to move on.I hope it turned out ok nonetheless! Edited November 2, 2015 by ChristopherC 1 Quote Link to comment Share on other sites More sharing options...
bandini Posted November 2, 2015 Share Posted November 2, 2015 Looks good to me! Care to share a hip file? I'm working on fire right now - having some tough time getting the look I'm after. I'd be curious to see your settings. -Adam Quote Link to comment Share on other sites More sharing options...
ChristopherC Posted November 3, 2015 Author Share Posted November 3, 2015 Thanks Adam!My scene is a bit of a mess to share because it is split in two .hip files—one for the simulation part done in H13, and the other for the shading/rendering in H14. Not that I'm enjoying this convoluted workflow but I don't really have the choice.In any case, there really is nothing special to it. The simulation part, as said previously, rely mainly on applying a Wave CHOP (type “pulse”) of high frequency mixed with some noise onto the temperature parameter of the Source Volume DOP. There's also similar CHOP animations—but with a lower frequency—applied to the disturbance, shredding, and turbulence shapes of the Pyro Solver DOP to add a bit of variations. Then I only tweaked these a bit more, cranked the buoyancy lift to 18, the cooling rate to 0.95, and lowered the temperature diffusion to 0.05. Oh, and the field being rendered is the temperature one, not the heat.As for the shading, it's the default Pyro shader on which I tried to get sharper edges for the fire, using the field shape ramp. I couldn't figure out how to get a nice color using the artistic ramp so I falled back using the “physical” mode and did most of the job in comp. Below is how it the render from Houdini looks like. I hope this helps—if not, let me know which file(s) you're after! Quote Link to comment Share on other sites More sharing options...
bandini Posted November 3, 2015 Share Posted November 3, 2015 Very cool. If you can, send me a .bgeo (one frame) of the fire. I recently figured out quite a bit about the fire shading ramps and how to get some nice colors with the artistic shader. I can try it out and send it back to you or post it here. Quote Link to comment Share on other sites More sharing options...
ChristopherC Posted November 3, 2015 Author Share Posted November 3, 2015 Sure thing, that would be great! The frame attached is the same as the one rendered in my previous post. Thanks! fire.bgeo.gz Quote Link to comment Share on other sites More sharing options...
bandini Posted November 3, 2015 Share Posted November 3, 2015 My go at it.. I don't like to go to pure white at the peak heat of fire, as it gets really ugly when comped if you have to lower the exposure. The way I have the ramp set up here, lower exposure will still have good color values. So, you would still need some compositing to white out the highlights, but that is pretty normal to do. I generally do the fire ramp by going for decent, middle-saturation rusty-colored values and pumping the intensity up a lot, which adds saturation. I'm not sure why you were simulating in H13 and rendering in 14... Was there a reason you could not do both in H14? The file I'm enclosing is H15. Hope you can check it out. -Adam FireShader_01.hiplc Quote Link to comment Share on other sites More sharing options...
ChristopherC Posted November 3, 2015 Author Share Posted November 3, 2015 (edited) Nice one!I've managed to open your file in H14 and I can inspect the pyro shader but maybe some parameters are missing, I don't know. I'm currently trying to download H15 Apprentice to have another look at your scene (since I can't seem to be able to render it in H14), but I'm currently in Vietnam and Side Effect's servers have never been too cooperative with the connection from here, so I'm not sure if I'll manage to download it at all. In any case I'm surprised to see this color ramp of yours! I am pretty sure that I had one matching at 90% what you've got here, including similar intensity values. Not sure what I did wrong then.Since I am a total newbie, I've been wondering if, for an element like fire that isn't influenced by lights (as far as I understand it), there is an advantage at getting as close to the final colors as possible? Wouldn't it be easier and more flexible to render a simple greyscale image representing the luminance and simply define the colors in comp? I guess it wouldn't work for an accurate blackbody shader like this one but it could otherwise possibly do the trick?As for the reason behind my H13/H14 workflow, it is simply because my laptop cannot deal with H14's Scene Viewer without crashing but the rest of the UI and Mantra work well.Thanks for sharing! Edited November 3, 2015 by ChristopherC Quote Link to comment Share on other sites More sharing options...
bandini Posted November 3, 2015 Share Posted November 3, 2015 About rendering out the raw temperature values and recoloring in post... Some people do something similar, but usually I see it rendered in a RGB ramp, rather than greyscale. A little easier to isolate different intensity areas of the flames for compositing. Some great info on volume rendering here: http://magnuswrenninge.com/content/pubs/ProductionVolumeRenderingSystems2011.pdf 1 Quote Link to comment Share on other sites More sharing options...
ChristopherC Posted November 4, 2015 Author Share Posted November 4, 2015 Aaah, I think that I saw these RGB ramps somewhere already. Good to know!Also thanks for sharing this paper! The blackbody shader is quite well described by Sony. It's probably only an illusion but at first glance its basic implementation seems to be easy enough. I'm wondering if this is how Houdini's Pyro Blackbody VEX node (used by the pyro shader) also works? And if so, why does it gives me such a yellowish color in my case? It looks like it's not remapping the colors onto the temperature field, even though I've just done more tests to try to fix this.Weta refers to the blackbody radiation through the paper NFJ02 which looks quite technical but making searches on Google based around the “NFJ02” keyword yields results with some more fire-related papers. Might find some good ones in the lot!What's sure is that I've got a lot of reading for the next time! Quote Link to comment Share on other sites More sharing options...
bandini Posted November 4, 2015 Share Posted November 4, 2015 I think Houdini's blackbody is pretty similar to the sony one. Using the blackbody shader on your file in H15, I was able to get very similar results to the artistic ramp I did, without too much tweaking. Color of the fire comes from temperature, following the blackbody description. Lower temperature should give redder, warmer color. Higher should get more yellow, getting whiter and bluer. Try lowering your blackbody temperature and substantially increasing brightness. Same principle as the artistic ramp... Get good color values, then pump up the brightness. If I remember, I will upload your file tonight with the blakbody shader, showing how to set it up correctly. Quote Link to comment Share on other sites More sharing options...
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