I am having a problem rendering the particle, for some reason it doesn’t have alpha channel on it. Is there anyway to turn the alpha render on?
Thanks.
Do you have Additive mode enabled? That causes the particles to render self-illuminated but with no alpha.
Yes, force additive is on. Is there anyway around it? Since I need the alpha channel as well as force additive to get the wispy look.
You render out another pass where the color is white.
- Chad
I tried using override with white however the result is not what I’m going after. I’ll try to use the force additive as an alpha layer on the white layer. Hope this will work.
Additive mode is cumulative, just as alpha should be. A white particle color, rendered additively over a black background will give you the correct alpha pass. Don’t override the density.
I’ve been using krakatoa for a while now and never used additive mode. Can anyone give some tips on why\what\how they used additive mode and what situations is good for?
Fred
There’s no need to sort the particles. So in theory you could reduce memory overhead and multithread like it’s nobody’s business.
On a practical side, it allows you to do accumulative rendering effects. Like glowy energetic stuff.
Wishlist… How about a Maximum rendering mode, as an alternative to Additive? Would prevent the render from “gumming up” in dense/bright areas.
en.wikipedia.org/wiki/Maximum_in … projection
- Chad
Now this is a looong story.
When our proto-Krakatoa renderer was born, it was an additive renderer. In fact it wasn’t even called Krakatoa and was a stand-alone application we used to render Doc Baily’s Spore particles for the movie Stay.
Here is the original Image Savant page:
imagesavant.com/
These images were produced with Doc’s own renderer, we just wrote something similar but orders of magnitude faster which also did motion blur and DOF.
So if you look at these images, you can see some cases where additive mode can be useful - accumulating billions of low-density particles can produce fantastic images where multiple particles produce glowing effects. It can be also useful for plasma and fire - see the comparison of FumeFX rendering and Krakatoa Additive Rendering on our WIP page:
software.primefocusworld.com/sof … ering_Test
So the Volumetric Rendering (the true birth of Krakatoa) was a second thought - we had to do silt for Superman Returns and we already had a massive point renderer, so “all” that was missing was shadow casting and volumetric shading.
In Krakatoa 1.1.2 and earlier, Additive Mode was a special mode that used a separate code path. The particle color was taken, modulated by the Density and accumulated in the pixels, just like in the proto-renderer. For volumetric shading, the particles were processed quite differently. The beauty of the old approach was that in theory one could draw the particle additively and discard it, so it needed no memory at all (except for the frame buffers). We never implemented this in the commercial Krakatoa, but the original particle renderer for Stay worked that way so it was very efficient - read/draw/discard. We had a wish logged against it for Krakatoa, but then in 1.5 we realized that rendering with no Absorption and Diffusion but 100% Emission is effectively the same as the old Additive Rendering mode, thus we made it possible to mix volumetric and additive rendering within the same pass, as shown here:
software.primefocusworld.com/sof … hading.php
Also, in our tests with FumeFX, we also tried to shade the Fire as additive and the Smoke as volumetric:
software.primefocusworld.com/sof … g.php#Fire
I hope that looking at the above examples will give you an idea why Additve Rendering can be useful.