There are plenty of Maya HDR (High Dynamic Range) tutorials and resources floating around, but here's a quick, definitive guide to setting up a Maya scene for mentalRay/HDR rendering.

First of all, make sure you are happy with the rest of your scene. HDR should really be the last step after modeling and texturing, because test renders tend to take a while. I will usually test my scenes with a simple 2- or 3-point lighting rig (sometimes just the default light will do). Once I'm happy, set up HDR lighting for a more realistic feel.

If you do not have any HDR images already, you can find some at the Light Probe Image Gallery.

Here's the scene so far. Notice that we only have a ground plane and a couple of simple primitives:


Sample Scene

Now, let's set up mentalRay. We need Final Gathering turned on for HDR to work. Change the render engine to mentalRay, and select the Production: Motion Blur profile. Now, we can take a look at some FG settings:


Render Globals: Final Gathering

I've set up the min. and max. radius relative to my own scene. There are more in-depth guides around, but a general rule of thumb is to set the max. radius to 1/10th of the total width of the objects (excluding ground planes) and the min. radius to 1/10th of that. If you find you're getting artifacts in areas of high-detail, try lowering these. In this case, I have set min: 0.09 and max: 0.9.

I've used 1,000 rays for this scene. Again, if the quality isn't high enough, you can raise this - but be prepared for longer render times.

If we turn off the lights and set the Environment Colour to around (HSV) 0, 0, 0.75, mentalRay will use that to light the scene. We can see that Final Gathering is already doing an adequate job. However, the light is uniform all around and lacks depth.


Initial Final Gathering render