I use KrakatoaSR along with C4D, but I have a question to the Max and Maya user who have a more evolved Krakatoa-plugin.
How do you visually integrate the Krakatoa-render in your scene when Karakatoa seems not to render any shadows on non-particle-objects or is that possible with your plugins ?
In C4D (with Krakatoa (Effex)-Plugin), Krakatoa is performed as a post-effect and added after the main rendering (Vray, Iray, AR), but only the particles have a shading, no krakatoa-shadows can be produced from the particles onto non-particle objects in the scene.
Here is a first rough test I made: http://www.youtube.com/watch?v=tjLq6udb60w&feature=youtu.be
As you can see, no shadows are produced by the particles on the floor, wall or the Buddha.
Shadows can be generated by SR. It’s up to you to actually use the shadows, though. There is no build in function to return an image with the matte objects with the shadows projected onto them.
It’s probably better if you don’t composite the Krakatoa render directly onto the main rendering. You should probably render Krakatoa first. Otherwise you wouldn’t know what the shadows would be until it was too late.
Yes, in both Krakatoa MX and SR, you can generate a special-purpose “deep opacity mapping” EXR file which contains several layers (but no RGBA data). One layer contains the Z distance to the closest particle. It can be assumed that the Attenuation at that point is changing from zero to a non-zero value. One or more layers follow, providing the Attenuation values at a specified linear or exponential step. This way, it is possible to determine the amount of light that was absorbed at any point is space behind the initial “hit”.
Krakatoa MX ships with a special Shadow Generator which lets the user load pre-saved attenuation data and calculate the shadow at any point in space, then mix it with the results of standard 3ds Max Shadow Generators (e.g. Shadow Maps, Raytraced Shadows etc.) for the geometry-to-geometry component. As Chad mentioned, Krakatoa SR does not provide a loader for this type of data yet.
In the future, we intend to also support DTEX deep shadows saving (right now Krakatoa SR only supports the loading of such files saved from Renderman-compliant renderers), and we will investigating Deep Compositing techniques using OpenEXR 2.0 which solve the same problem in a different way.
The Deep Opacity map is conceptually quite simple. It might not be too difficult to add support for that. We’re considering doing it in a fragment shader in our SR implementation, loading it as a 3D volume and doing all the sampling in OpenGL.
An alternative is to actually convert your matte objects into particles using the PRT Volume (or PRT Surface when that becomes available, or just implement your own). This way you can render the matte objects directly in Krakatoa.