Fire doesn't affect the scene

[CG_FORM]

Hello,
I am trying to set up the rendering of my scene. I made simulation etc. and now tweaking the fire options. I noticed the fire doesn't affect the scene at all and is not present in any render elements passes (lighting, self illumination etc.) Smoke is present. I am not sure what is wrong. I have the GI ON, I tried to switch on and off the "Create Fire Light" option - nothing works.
Can You help please?
All the best
Piotr

[CG_FORM]

OK. I figured out that was because of Fire Multiplier - When I set Multiplier to 60 it started to affect the scene. But with multiplier 60 the fire itself looks burn out and not sure how to have both: fire affecting the scene and not to be burned out itself. And why fire is not present in any of the render elements?

[Svetlin.Nikolov]

Hey, the option you are looking for is Light Power on Scene - boost that 60 times...


Also, your flames are small, so when you are using the default grid based self shadowing, the light grid's resolution might not be enough to consistently fit the flames. Try increasing the light resolution option, but watch out because it might slow down rendering if yiu increase it too much.

Hope this helps, cheers!

[CG_FORM]

Hey, the option you are looking for is Light Power on Scene - boost that 60 times...


Also, your flames are small, so when you are using the default grid based self shadowing, the light grid's resolution might not be enough to consistently fit the flames. Try increasing the light resolution option, but watch out because it might slow down rendering if yiu increase it too much.

Hope this helps, cheers!

Hi Svetlin,
Thanks a lot, mate but even If I set the Light Power on Scene to 1000 there is still not enough lighting from flames in the scene. I set the grid based self shadowing to 100 - doesn't work either. Only the multiplier seems to work although it makes the flames burned out. The weird thing also is there is no fire in the render passes. Smoke is in couple of them but not the fire.

[Svetlin.Nikolov]

Ah, here is more info on the render elements: https://docs.chaosgroup.com/display/...Fire+and+Smoke

I still suspect that the fire is too small to actually contribute to the scene - you could verify this by experimentally switching from Grid based to Ray-traced self shadowing - this way there won't be a light grid and the illumination will be distributed entirely by GI, showing exactly how strong the realistic illumination will be. Please give this a try and share the results.

[CG_FORM]

Hi Svetlin,
You are probably right as for the fire source (they are too small) - see attached. These are few small objects merged together with shell modifier. As for the render elements - don't know what is wrong. I have the sim set to Volumertic mode and still self illumination and vray atmosphere passes are black. Smoke is visible in other passes (like Light select, reflection, shadow etc.) Maybe I have something set up wrong as mesh? BTW - is it possible to set up simulator the way the flames come out from the emmiter more precisely?

[Svetlin.Nikolov]

Render element setups sound correct - are you using V-Ray 5 and Phoenix 4.20?

As for emitting more precisely, can you elaborate more? I am not sure how you have it set up right now, but you could parent the Simulator to the moving plane so the plane movement does not require you to use many steps per frame to get an uninterrupted trail...

Cheers!

[CG_FORM]

I use Vray Next 3.2 and Phoenix FD 3. Sorry for my english. As for the flames coming out the emmiter I meant if the flame could be emitted precisely from the object. Right now there is some offset between hole (flame emitter) and flame itself (as You can see on the attached image above). In my scene there is no movement since that is still image. I simply added wind force so the flames go along the plane. And one more thing. If I wanted the flames to be more realistic in terms of detail - is it only the matter of higher grid density or something else?

[Svetlin.Nikolov]

Ah, you might use more steps per frame for the gap between the emitter and the flames, but watch out because this might smooth out the flames you might lose details.

Regarding render elements, can you try a simple test so we'd know if we are on the same page or something more exotic is happening - please start a new scene, create an Explosion toolbar preset and run about 20 frames; add V-Ray atmosphere and self-illumination render elements and check if something shows up there; Just tried this with Phoenix 3.14 and V-Ray Next 3.2 and worked okay. If this also works for you, then we gotta check at your specific scene, looking for something special. If even the toolbar preset does not work, then we'll know to shift our focus elsewhere...

As for getting more flame detail - yes - increasing the grid resolution would help, tweaking the render curves as well, perhaps you've already seen Hammer Chen's tutorial here (http://phoenixfd.cgrecord.net/2019/0...re-trails.html), and also you could use Resimulation to increase the resolution without losing the behavior and shape of the sim (https://docs.chaosgroup.com/display/...ation-Overview), though for fast flames like your setup just increasing the grid resolution without resimulating should now change the behavior too much either...

[CG_FORM]

Thank You so much Svetlin. Will test that and let You know!

[CG_FORM]

Thank You Svetlin for the flames advices now they work much better after I adjusted the curves. As for the render elements I did like You wrote - created new scene, added box and created simulation with smoke and flames. Since the beauty pass includes all elements, smoke is visible in GI, fire doesn't show up in any (like vrayselfillumination or vrayatmosphere). Smoke also doesn't show up in Vrayatmosphere pass too.

[georgi.zhekov]

Are you rendering with V-Ray CPU or are you using the GPU rendering? Some of the render elements are not supported on the GPU and this could be the reason for them to not show up.
If you're rendering on the CPU - can you send over the new scene with the box so that we can check what is going on?

Thanks!

[CG_FORM]

Are you rendering with V-Ray CPU or are you using the GPU rendering? Some of the render elements are not supported on the GPU and this could be the reason for them to not show up.
If you're rendering on the CPU - can you send over the new scene with the box so that we can check what is going on?

Thanks!

Thank You so much for help! Indeed it was because of rendering with GPU. Now when switched to CPU fire is visible! Thank You so much!!! You have helped me a lot.

If I can ask one more question:
I am rendering such scene and I am wondering what are those lines I marked and how could I get rid of those small dots in the smoke area? The object with fire sim linked are moving along the spline.

[Svetlin.Nikolov]

Hmm, if you are using drag particles in the scene, then this might be the drag particles rendered as points by a particle shader with motion blur?

[CG_FORM]

Hmm, if you are using drag particles in the scene, then this might be the drag particles rendered as points by a particle shader with motion blur?

Is the "drag particles" some option in Phoenix? i noticed that appeared when I chose "Fire/Smoke from FumeFX" from presets menu in Rendering section.