When I use a custom curve to colour the fluid, the fluid lights up nearby surfaces. As soon as I switch to use blackbody radiation to colour the fluid, the lighting of nearby surfaces stops. This is why I was left wondering if the fluid simulation is hooked up to Lumen? On top of this, I still do not see the fluid casting shadows.
Lumen and niagara fluids is somewhat interesting, and lumen’s connection to niagara in general is a bit of a mess in my experience.
RTR has niagara particles in the acceleration structure, but I don’t believe lumen does. Lumen does use screen-space reflections and global illumination, so niagara fluids can cast light on a surface in screen-space, but I don’t know if it’s shadowed.
Niagara fluids can receive lumen reflections, but they cannot cast lumen reflections, at least in my testing.
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Well, according to my tests, I can get lighting and reflections for fireballs. The only stipulation is that it has to use a custom colour (e.g. something other than black body radiation). Here it is in motion:
So the color variable is the only var that appears to be affecting the desired behavior?
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Yes, sir. In the Niagara system, there is Emitter Summary for the gas emitter. Under Render, there is the Render Temperature. Setting it to Black body seems to disable global illumination. Here is a video where the GI seem to work, when the Render Temperature is set to Curve.
Are you from Saskatoon?
I am gaining control over the fluid simulations in Niagara. Here is an effect that looks similar to the effects in Ikaruga.
I also noticed something. Even when I am using a custom colour curve, the fireballs do not light the walls. The walls only get lit when there is a floor reflection close to it, so basically the lighting of the walls is purely indirect, generated by the floor alone. So I’m not getting what I’d expect. I apologize for the misunderstanding on my part.
Canada?
Hmm, this is interesting. As an easy cheat (it’ll depend on how the emitters in your fluids work), you could always attach a point light to your fireball center and have it propagate lighting analytically.
Also, out of curiosity, do you have lumen enabled?
How do I enable Lumen?
Sorry. My old eye surgeon went by the last name Blackwell. Funny that I run into another Blackwell when dealing with optics. LOL
And that’s the thing. I am wondering if I can run the data through Marching Cubes, to generate an isosurface. From there, that can be used for collisions, as well as a lighting surface (by setting the V colour component to like 100).
Here is another video or two:
I’ve changed the Render Temperature Range to x = 0, y = 0.01, and it surely lights up the surrounding wall and floor when using Black Body as the colour scheme. I am stumped as to why it didn’t work before.
The remaining question is: why do the walls and floor light up in the first place? It seems that the reflections are in the wrong place in spacetime, and they fade over time after the light source is long gone – there’s a lag. What is all of this about?
I also notice that the light fades over time when I disable (close the eye icon of) the scene’s directional light.
Now that is a funny coincidence, and no relation alas, but I like your sense of humor nonetheless.
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Woah, that is absolutely baffling, and I do love the affect you’re trying to achieve with this work. You may be interested in the developers’ of Returnal’s talk on developing particle fx, including marching cubes used in UE4:Can We Do It with Particles?: VFX Learnings from 'Returnal' - YouTube
My knowledge of Niagara is a small fraction of what I’d like it to be, but I’m fully stumped on your lighting behavior. I might check your PPvolume to make sure you have no reflections or GI enabled to check if it’s direct or indirect lighting (narrows down lighting behavior), and in addition to that, try the other vis modes.
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Well, thanks again!
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