I just ran into a problem. My idea is to simulate fire with FumeFX, use a FumeFX Loader to save a PRT sequence of my sim, then load the PRTs with a seperate loader and use Krakatoa PRT Birth to emit Pflow particles at the positions of my PRT particles. After that I want to try to create a fire out of crystals with shape instances, just for the sake of it ;D.
While working on this little project I experienced some render issues when trying to render either the FumeFX Loader or the PRT Loader that loads the cached sim. Unfortunately, it turns out black. I probably know what you’re thinking now^^. I placed two omni and one spot light. Krakatoa only renders the pflow particles I used to drive my fume sim. In the Krakatoa settings PRT Loaders and FumeFX Loaders are enabled. I see the particles in the viewport and when rendering the FumeFX Loader I get the particle count of around 450k in my render view but I don’t see any, the alpha is black, too. I tried a color override without effect. I don’t know if it’s normal but I don’t even get any particle count when rendering the PRT Loader with cached PRTs. One additional info: I only emit in fire, not in smoke.
This particle rendering process isn’t necessary for my project, but I still wonder how it can be solved or what I do wrongly. Might there be a fume channel that f*s everything up? Looking forward to any help.
specs:
Krakatoa MX2
Fume 2.1
Max 2012 hotfix 4 (I think it was…)
I am not sure I follow (since I am not that great at FumeFX stuff).
Can we create a list of simple steps to reproduce the problem? (I went to a German school back in the day and creating “Stichpunkte” is in my blood now )
Something like
*Create a FumeFX simulation grid
*Create a PFlow simulation to emit from
*Create a PRT FumeFX object from the FumeFX
–At this point, you could use Particle Data Viewer to see the channels of the PRT FumeFX object and inspect for strangeness.
*Save the PRT FumeFX as PRTs to disk
*Create a PRT Loader from the PRT sequence
–At this point, you can also use the PDV to see the channels that are coming in. Are there any particles in the PRT file at all? Are there any channels that are not there or 0.0?
When rendering, if you don’t get any Alpha, chances are that there are no particles loaded - the Krakatoa Log Window, the Memory rollout and the PCache right-click menu are possible places to actually SEE the count and memory usage after a test render. If the particle count reported by the renderer / PCache is NOT 0, then make sure the Density channel is not 0.0 or close to 0.0. PRT FumeFX will tweak the density values to represent the values in the simulation, but if the scale of the simulation is too large, the Density values could be tiny. In that case, setting the Final Pass Density to Exponent of 31 can be a quick test to check if an Alpha channel will appear.
If the above steps are not what you were doing, please correct.
Then, once you have confirmed whether there are any particles in the PCache after rendering a frame, we can start looking at what else could be wrong…
haha, ya stichpunkte are always helpful ;D. I just tried to recreate the issue and found something. When creating a fume grid with a simple source and emit a few frames with saving fire and smoke channels I can render the sim through a PRT FumeFX with “emit in smoke”, or “emit in fire” or both checked. When turning of “Simulate smoke” in fume, the PRT FumeFX doesn’t render the fire particles but shows them in the viewport. It shows 57 cached particles but renders black. Playing around with the density doesn’t have any effect. The data viewer shows position, fire and color values for the particles. Fuel and density are 0.0, I don’t know if that’s normal. JUMP IN TIME / Just tested the sim with smoke again, and now the fire particles have density values D:. Might this be a fume bug, that no density for the fire channel is saved to the .fdc when simulating without smoke?
PRT FumeFX creates the Fire particles as Additive. They should have an Emission channel containing the color which, when rendered with >Use Emission enabled, should appear in the RGB channel. Additive Rendering in Krakatoa is basically Color and Absorption set to Black, while Emission set to the color. Density channel of 0.0 does not affect the Emission, but the Global Density Multiplier (and the option Emission Strength) will.
If your Use Emission option is disabled, Krakatoa will attempt to render the particles volumetrically, but will find Color and Density to be zero and will show nothing. You can of course work around this by adding a Magma modifier and setting the Density channel to 1.0 to make the “fire” particles render volumetrically instead of additively.
Okay, with emission turned on I see the particles . Thank you. Do have an idea why the density is zero without smoke and actually has a value with smoke?
A particle that is half-way between fire and smoke will be half-additve / half-volumetric. Otherwise the particles in the fire area would have a very clean cut distinction between fire and smoke, but we need the fire to gradually blend into the smoke. When there is no Smoke channel in FumeFX, all particles are Fire only, so they don’t NEED a Density.
You can see a discussion of Additive vs. Volumetric shading here to give you a better idea how Krakatoa deals with such cases: thinkboxsoftware.com/krak-mi … and-volum/
I continued with my experiment and I’d like to share two images. I think one can create really interesting shapes. The attached images serve a technical purpose…boring composition
)
. Thank you. Do have an idea why the density is zero without smoke and actually has a value with smoke?
