Mental Ray Rendering

Today I was having a quick look at some of the render options within Mental Ray in Maya, and I have to say, it shits all over the Maya Software renderer. As a part of the course we were asked to design a character in Maya that would eventually get rigged and animated, I assume using Maya's IK and bone animation tools...or whatever, I haven't really looked to much into animating yet, that's still to come.


Anyway, as I'm looking at placing CG into real world environments, I thought I'd create a robot...which seems to be becoming a recurring theme on this blog... But this robot wasn't a large robot that turns into a car and destroys everything within close proximity, I was thinking a little more realistically about this one. I've always been a bit of a sci-fi fan, but believable sci-fi. So I was looking more at a design of a robot along the lines of the Isaac Asimov/Will Smith type genre. I was also influenced by the visual style of the Chris Cunningham video for Bjork's all is full of love. These to me seems to represent a more realistic representation of what robots will one day represent. This film clip and Asimov style narrative also raises a lot of philosophical and sociological questions, but I'm not getting into that right now. Needless to say it's a bad arse clip with some equally bad-arse CG and model making.

Chris Cunningham and Bjork's all is full of love.

Sonny the NS-5. IRobot.

But anyway, I've digressed into talking about robots again...Damn! So, as I was saying and as is the name of this post, I was looking at Maya's mental Ray renderer, specifically Global Illumination and Final Gather. Up until now whenever I had modelled, textured and rendered any object, I had strictly used Maya's ray trace shadows and reflections and be done with it. Although high quality ray trace shadows can look very effective, there is still a something intrinsically CG them. This is where Global Illumination and Final gather come in. 

When rendering with just ray trace shadows, the geometry receives light and casts shadow as it would in the real world, but it doesn't reflect light onto other objects or ambient lighting. This ambient lighting is such an important part of rendering and can take a good render and make it look a hell of a lot more realistic.

The first rendering here of my robot here was done using just ray trace shadows. Although the shadows are mathematically correct they don't look realistic.

The second render here is without Ray Trace shadows, but instead has used Global Illumination and Final gather to calculate the lighting. The Global Illumination function causes the light source to emit virtual photons into the scene and them map them as they decay and interact with the geometry in the scene. I have initially had a few issues with getting this to work but the final result gives a much more true to life representation of the objects.

This light bouncing and ambient lighting effect can been better demonstrated when getting up close to the geometry to see its effects. Again, the first rendering is with Ray Trace shadows turned on, without Global Illumination or Final Gather and the second is the opposite.

Note the darkness of the shadows in the top render as opposed to the ambient light in the shadows in the bottom render. The effect is quite subtle but I think makes a big difference.

So there you have it, a brief look at the finer point of Mental Ray and of course more robots. I'll be looking into how to actually animate this guy in coming weeks and eventually try and drop him into some match moved footage. Perhaps creature comforts style talking about what it was like being raised in Bristol...