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Hi,
I am facing quite a complex issue. I am integrating PhoenixFD fire into real shot footage. The fire reflects in some of the holdout geometry of the tracked shot, and illuminates some other parts of the geometry.
Since V-Ray does not have any concept of matte illuminators, where you can define certain light source contribution to be additive on the matte objects (definite that the light is added to the scene instead of re-creating light already present in the scene at the time of shooting), I had to resort to have light catching geometry not being matte objects, but instead just very dark gray diffuse material, which works well in conjunction with rendering against black for compositing. Other holdout objects, that reflect the flame instead of receiving its light, remain matte objects.
Now, the big problem here is that compositor requires the illumination on the scene from the fire to be separable from the fire itself, so it can be tweaked separately. I found this to be an impossible task. Main problem stems from the fact that Phoenix FD fire by default does not have any alpha. It has three fire opacity modes: Fully visible, Use smoke opacity and Use own opacity. Unfortunately, setting mode to anything else than Fully visible will radically change the way fire looks, and makes it look completely different to the already approved look, so that is not an option.
Other things I tried:
- V-Ray light select render element does not allow to pick PhoenixFD grid as a light source.
- I tried to get just matte of meshes illuminated by the fire, but fire volume does not occlude those matte channels.
- I tried to get atmosphere render element, but it contains only fire, without its reflection in the reflective mattes
- I tried to add a few different reflection render elements, but none of them contained reflection of the fire
- I tried to add VrayLighting element but it is again not occluded by the fire
So I just can not find any way to separate illumination of the surroundings from the fire itself.
I am facing quite a complex issue. I am integrating PhoenixFD fire into real shot footage. The fire reflects in some of the holdout geometry of the tracked shot, and illuminates some other parts of the geometry.
Since V-Ray does not have any concept of matte illuminators, where you can define certain light source contribution to be additive on the matte objects (definite that the light is added to the scene instead of re-creating light already present in the scene at the time of shooting), I had to resort to have light catching geometry not being matte objects, but instead just very dark gray diffuse material, which works well in conjunction with rendering against black for compositing. Other holdout objects, that reflect the flame instead of receiving its light, remain matte objects.
Now, the big problem here is that compositor requires the illumination on the scene from the fire to be separable from the fire itself, so it can be tweaked separately. I found this to be an impossible task. Main problem stems from the fact that Phoenix FD fire by default does not have any alpha. It has three fire opacity modes: Fully visible, Use smoke opacity and Use own opacity. Unfortunately, setting mode to anything else than Fully visible will radically change the way fire looks, and makes it look completely different to the already approved look, so that is not an option.
Other things I tried:
- V-Ray light select render element does not allow to pick PhoenixFD grid as a light source.
- I tried to get just matte of meshes illuminated by the fire, but fire volume does not occlude those matte channels.
- I tried to get atmosphere render element, but it contains only fire, without its reflection in the reflective mattes
- I tried to add a few different reflection render elements, but none of them contained reflection of the fire
- I tried to add VrayLighting element but it is again not occluded by the fire
So I just can not find any way to separate illumination of the surroundings from the fire itself.
