Hi, I've really been struggling with making a pyro sim that handles a moving object and also has short flames. The effect I'm after here is a ball of fire moving from one point to another, the goal is a flaming meteor.
I'm clearly doing something very wrong because I can't seem to get the fire to maintain shape while moving. It dims down to basically nothing the moment it moves.
One of the larger issues I'm having is just making really short flames. I'm used to cranking up the burn rate in FumeFx, to make it burn faster. But I don't believe that is how Houdini handles things. I've tried lowering the burn rate to 0.1, but that just kills the amount of fuel burned, not how quickly it is actually burning.
Attached you will find the hip file, it's really light to work with.
If you could give me any assistance I'd greatly appreciate it!
Thanks so much,
Jyota Malcolm
Moving fire pyro sim.
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- Jyota_Malcolm
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- Enivob
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What you can try is to add another trail, right after the scatter to spread out the fuel generating points you have created. This will trail the geometry, instead of calculating velocity. I also added the frame number to the random seed of the scatter to add more variety. I added a wrangle to set the value of the f@fuel on the points before the volumes are generated. This is another way to manipulate the intensity of the generated fuel. I activated the guide for the fuel, shown in pink/magenta. Think of your fuel as another object that you are animating. If it is not solid, then your flame will be weak.
Edited by Enivob - Jan. 29, 2019 23:54:02
Using Houdini Indie 20.0
Ubuntu 64GB Ryzen 16 core.
nVidia 3050RTX 8BG RAM.
Ubuntu 64GB Ryzen 16 core.
nVidia 3050RTX 8BG RAM.
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- Jyota_Malcolm
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Thanks so much for the reply! I guess I'm just expecting this to look more like a torch someone is walking with. I don't understand why the fuel goes in this long tube shape. It seems also that the fuel lasts for too long? It almost looks like it's not even burning on the right, it's just staying there.
Here is a video of kinda what I'm expecting: https://youtu.be/onZEcauMhtQ?t=24 [youtu.be] Or just any swinging fire in youtube.
Again thanks so much for helping!
Here is a video of kinda what I'm expecting: https://youtu.be/onZEcauMhtQ?t=24 [youtu.be] Or just any swinging fire in youtube.
Again thanks so much for helping!
Edited by Jyota_Malcolm - Jan. 30, 2019 11:50:20
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- Midasssilver
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Here ya go. I got you a lot closer to where you wanted to be. Some notes. Never have a scatter computer after the transform. This will make it re-compute every frame, slowing everything down. This also sucks if you cache your source, so try and avoid that.
Next, you had your timescale way too high. This prevents the fire from trailing behind. I reduced it from 3 to 1, and things got better. Also, you had a bezier curve on your source animation. I changed that to linear to get a smoother motion for your source. Add some turbulence to break up the shape, as opposed to disturbance. Turbulence creates big shapes, and disturbance should be used to break up those big shapes, not really by itself.
Hope that helps.
Next, you had your timescale way too high. This prevents the fire from trailing behind. I reduced it from 3 to 1, and things got better. Also, you had a bezier curve on your source animation. I changed that to linear to get a smoother motion for your source. Add some turbulence to break up the shape, as opposed to disturbance. Turbulence creates big shapes, and disturbance should be used to break up those big shapes, not really by itself.
Hope that helps.
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- Jyota_Malcolm
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Thank you for your assistance! That was a good call with animating the source after the scatter.
I've played with it some more and came to a few conclusions. Firstly, burn rate is different than fumefx burn rate. What I was wanting to play with was flame height. Burn rate should stay at 1 because it is how much of the sources fuel is burned per frame. When you have a low burn rate, the fuel gets left over and forms this trail of fuel from the moving object. So leaving it at 1 and then drastically reducing the flame height. I used 0.1 in this case. Then you can still play with the gas released (combustion scale in fumefx), turbulence etc while maintaing flame length. I still need to figure out how the cooling field and field range work.
This is far from perfect visually, but the solution is there.
I've played with it some more and came to a few conclusions. Firstly, burn rate is different than fumefx burn rate. What I was wanting to play with was flame height. Burn rate should stay at 1 because it is how much of the sources fuel is burned per frame. When you have a low burn rate, the fuel gets left over and forms this trail of fuel from the moving object. So leaving it at 1 and then drastically reducing the flame height. I used 0.1 in this case. Then you can still play with the gas released (combustion scale in fumefx), turbulence etc while maintaing flame length. I still need to figure out how the cooling field and field range work.
This is far from perfect visually, but the solution is there.
Edited by Jyota_Malcolm - Jan. 30, 2019 15:57:15
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- Midasssilver
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Yes, you want a very high burn rate, to get rid of any left over fuel. Cooling rate controls how fast the temperature cools, and therefore effects how fast fields (such as the color which are based on temperature) move through their respective ramp. As you decrease the cooling rate, you create a longer fire trail, that takes longer to turn to smoke, and as you increase the cooling rate, the fire will become smoke a lot quicker. One thing I would suggest is enabling Compute Min/Max on the dop import to find out what field ranges you are working with. Then you use that as the fit range for your fire color. You also use that data to determine what field range you use for control fields for the separate shaping parameters; The issue is visualizing that data numerically isn't very obvious.
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- Jyota_Malcolm
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