I’m having trouble getting my Krakatoa renders to look anywhere near as good as my straight fumefx renders- but I am a noob to Krakatoa.
The trouble starts when I try to save my PRT FumeFX particles with Copy Lighting to Emission enabled…When I load those up with a PRT loader I can’t get them to look the same as the PRT FumeFX by tweaking the Density and Emission settings (not sure how much they should need to be tweaked). What am I missing?
I know that Krakatoa doesn’t have all the shading options that Fumefx has with scanline rendering- but in general should it be possible to achieve rendering parity between scanline and Krakatoa minus Multiple Scattering, and other things that Krakatoa doesn’t support?
First of all, saving the Lighting to Emission means that the Lighting Pass Density at the time of saving will be baked into the particle sequence. As result, you won’t be able to change that in later renders (this controls how much light is attenuated as it passes through the particle cloud). So if you are trying to control the light scattering, you should not be baking the lighting (that option is for advanced users who have already figured out the correct settings and want to speed up the lighting process, especially when rendering 500+ million particles).
Second, FumeFX should generally be rendered in Voxel mode if you expect to get anything close to the standard FumeFX look. As mentioned elsewhere, we added the ability to render FumeFX directly because we had a missile trail shot in the movie G.I.Joe where rendering in Scanline or VRay would have required more than 64 GB of RAM, but Krakatoa could render with around 600MB of RAM usage. We got the basic volumetric look (using a red, green and blue light to tweak the rest in post) and passed it to the 2D magicians to integrate it into the shots. I would not expect Krakatoa to match the FumeFX rendering perfectly, but with the right settings it should get very close. Keep in mind that Voxel Rendering in Krakatoa is currently a lot slower than particle rendering, but work is being done to improve the situation in future versions.
Can you post an image of what your Scanline and Krakatoa renders look like so we can discuss possible changes?
Thanks for your reply Bobo. I don’t want to change the lighting after I’ve saved the particles. The problem I’m having is that things look pretty good when rendered with my PRT FumeFX (and would probably look better rendering in voxel mode- I’ll try that), but not good when those particles are saved with lighting and loaded with a PRT Loader. Since things are getting baked into the particle sequence- what should you do with the density and emission settings with the PRT Loader if anything? What are the correct settings and workflow to basically get the same result as with the PRT FumeFX?
The reason behind this all is that I want to render out “slices” of a fumefx sim as if the “Show Slices” option in the FumeFX modifier>Viewport panel affected rendering and not just the viewport. Using the PRT Loader culling options is the closest I’ve been able to find.
I see, now I understand why you want to bake the lighting (you want it to contain the influence of the culled portion of the particle cloud, right?)
The correct workflow should be: Save with Bake lighting, then check “>Ignore Scene Lights” and “>Use Emission”. Note that the Emission Strength value introduced in Krakatoa 1.6.x should match the Final Pass Density value to get the correct light intensity.
Please post a render of the PRT FumeFX and of the PRT Loader without Culling so I can understand what the difference is that you are seeing…
I decided to test the workflow and I think I understand your problem now.
I will try to figure out what was broken and will pass it to the developer to look at…
It is definitely not working the same as in v1.5.x…
I just tested with a PRT Volume instead and it produced EXACTLY the same rendering after Baking the lighting and loading with a PRT Loader.
So it seems that the saving of the PRT FumeFX with Lighting is broken somehow… Will continue testing.
Darcy localized the problem and suggested a temp. workaround until he posts a new build:
Once you have saved the PRT FumeFX with Emission as usual, on the PRT Loader used to load the saved data you can add a Krakatoa Channels Modifier (KCM).
*In the KCM, select the Output node (green) and change it to “Emission” channel.
*Select the Input node (default “Color” channel) and press the “Same Channel As Output” button or set it to Emission channel manually.
*With the Emission Channel Input node selected, hit the * key on the NumPad to add a Multiply operator.
*With the Multiply operator selected, hit SHIFT+D to create a Density Channel Input node.
As result, the Emission is multiplied by the Density and the resulting PRT Loader should render identically to the PRT FumeFX when >Ingore Scene Lighting and >Use Emission are checked.
I confirmed that it works with my Fume sim, and I was able to cull half of the cloud and peek inside to see how the light is falling off…
The left image shows the result of a simple FumeFX rendered with PRT FumeFX object as points. It was lit by two spots, one white and one blue, with all default settings otherwise.
The particles were saved to PRT file sequence using the option to save Lighting into Emission.
When loaded in a PRT Loader, with >Ignore Scene Lights and >Use Emission checked, the particles rendered overbright, like on the right image.
The trouble was that the PRT FumeFX manipulates the density of the particles based on the density of the source FumeFX sim, but it failed to multiply the Emission by the changed Density values and assumed Density as 1.0 instead.
The solution was to multiple the Emission by Density AFTER the loading but before rendering via a KCM, producing the left image without using any scene lights.
I’ve got things working better now- but the problem I’m having is after I save the particles and load them with a PRT Loader with a KCM applied per Bobo’s post- the fire doesn’t show up the same. Also if I don’t first turn down the Emission Strength on my saved particles then renders appear overbright. Tweaking this down I can get the smoke to match the PRT FumeFX but I don’t know why the fire is different. Feel free to tell me to go read the manual.
FumeFX’s Fire renders as Emission in Krakatoa, so when you change the Emission Strength the overall brightness of the fire is affected. In your case, you need to set the Emission Strength equal to the Final Pass Density when saving to PRT files (and increase the "Generate Emission from FumeFX Fire-> Multiplier to compensate. You’ll probably use whatever is there now times (1 / 0.4) since you are changing the Emission Strength from 1 to 0.4). This way the saved lighting won’t be overblown, and the fire won’t be reduced.
We are looking at ways to fix the workflow to make it less crazy, but this is what you need to do right now.
it is not necessarily a bad workflow IMO, great deal of control, but then again it isn’t a one-click solution either, apart from force additive mode not much of Krakatoa is a one click solution
