Category Archives: Visual Effects

November 24, 2016

Houdini Candle Flame Simulations for Ship Environment in Maya

Hello! Working on making a realistic candle flame and I definitely see a few issues I want to fix but don’t yet know how…

Final Houdini Output:

Here’s the current development of the candle flame.


#1 – The bottom of the candle flame where the initial flame shape comes from is showing up as a cube at the bottom of the simulation giving weird harsh corners. I used a sphere to emit candle flames from in the Pyro tab and have been tweaking settings to try and get it the way I want.

Fixed this part! Had to edit the falloff and border settings in the object source -> Create Fuel Volume Node.


#2 – The top of the flame is too wispy and when looking at candle flame references, you see that it’s more calm and even slightly rounded. What types of settings would help me with that?

#3 – Most confusing to me at the moment is the color gradient ramp I’ve been trying to play with in the SHOP network. By default it gives the Candle texture to the flame so it can be rendered, but when I go and tweak the gradient for the temperature color ramp in the texture settings, it simply doesn’t give me a seemly correct range. I have the settings to display from 0-1 (from one end of the gradient in the center to the other end of the gradient towards the least hot parts.) It seems to give me one color and one color only no matter how I tweak the range settings and the ramp. 🙁 I want it to be more blue towards the bottom/center and branch out a brighter orange but it just doesn’t seem to want to give me a blue center with an orange outer gradient.

Edit as of 12/06/16: Got things working a bit. Deadlines mean compromise once and a while so I developed the look the best I could through Houdini. From there I moved on to exporting out the Pyro from Houdini as a .VDB sequence. Ran into a few issues on that road as well where bringing them into Maya, Renderman’s VDB visualizer wasn’t happy with my .VDB files.

The weird issue I was having was that for some reason, when I saved out my .VDB files from Houdini I saved them to a shared Drive on my computer and for some reason that was corrupting the files. They would end up being anywhere from 30,000 – 90,000KB and then when loaded into Maya would produce an error saying that they weren’t .VDB files when they obviously were.

So I tried saving them to the Desktop and two things happened: The files sizes dropped dramatically to 300KB-3,000KB per file and they actually were readable into Maya.

So that’s something to remember if you are ever getting a “IoError: not a VDB file.” and you feel like you are correctly exporting.

The final result I got going on is in the below image. My main issues now is, the flame honestly just doesn’t look intense enough in terms of brightness, and on top of that it looks like there’s still some weird information being provided about the bounding box rather than just the flame. I had a PrimVar for density plugged into the density color before and I was getting super harsh black bounding box artifacts so breaking that connection and making the density color white got rid of that!


I am also a big proponent of giving credit where it’s due! I was able to make this simulation loopable which was a super valuable part of this simulation via this lovely tutorial found below!

I eventually want to take the candle light into Maya and do a render, because I’m working on a ship cabin at night mostly with warm candle light on the interior and bluish moonlight on the exterior coming in the windows.

Working on this above part now! 😀







Made a support post on the WIP Houdini forums as well:

Here’s where I went for help on the Renderman Forums as well:

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