GI the Rambo way.

If Rambo ever got the idea to do some global illumination he would do it the most brute force way there ever was. In mental ray this method is called path tracing.No mumbojumbo, no cryptic controls or shaders.

It is all super mega ray tracing, which means two things:
1. It's super accurate.
2. It's super silly slow.

There are a few things to keep in mind when path tracing. Most important is to use only the path_material, and since this is brute force there are no photon shaders or such needed. In your render settings be sure to disable all photon techniques ( GI and caustic ) as well as final gather.

As we are about to use pure ray tracing as GI we need to make sure that our standard ray tracing depths are high enough to distribute the light through out the scene.

Last but not least, we need a ton of samples to get the render smooth.
( You probably need to look into the oversampling_lens )

Here is an example of the difference between samples, these images were rendered
with min/max 2/2, then oversampled with the oversampling_lens.
Those over samples are the image annotations.

Note. render times are per full frame (415x415)
the images were cropped for easier compare.

In conclusion.
This special technique might not be something you would want to use in your pipeline. But it's always a plus to know as much as possibly about your tools of trade.

The mia_lens_bokeh shader.

Todays mental ray experiment focuses on lens artifacts
such as chromatic aberration, scratches and blooming/glare.

First of: chromatic aberration.
Chromatic aberration is an artifact often seen when using
low end or wide angle lenses. Due to the colors different wavelengths
and the differing index of refraction on the lens, the color spectra
gets separated, mostly on high contrast parts of the image.
( for a more correct explanation take a look at this wikipedia page )

One way to produce this effect is to use the new
bokeh shader shipped with Maya 2008 (mia_lens_bokeh).
The result produced this way will not be at all physically correct
but will give a similar look to the rendering.

Ok, lets see some example.

Top image image taken with a higher quality lens producing no chromatic aberration.
Bottom image taken with a wide angle lens producing substantional chromatic aberration.

Next let's look at the result we get from our bokeh shader

Notice that we only get the effect on the out of focus regions.
This is due to the use of the bokeh shader which is a depth of field shader.

The setup to get this result is really quite simple.
What you need to edit on the shader is the following:

• Check the "Use bokeh" check box
  
• higher the bokeh samples (or the image will render black)
• load a color map texture in the "Bokeh" slot

The texture used in the rendering above is a really crude RGB map
that look like this.


Thats all on chromatic aberration for now.

Bravia #3

Heads up for the third sony bravia TV commercial.
This time its all stop motion made by passion pictures.
Thought this clipp would be the perfect start to this blog
( both bunnies and colors! ).

Kinda sandboxing here.

I really don't have any things to blog about at the moment.
But I'll add an image just to test this new awsome blog.

Ok. that did not work at all, I'll give it a try later on.