The render engine analysis series: mental ray

11.10.2017 Home >Blog >The render engine analysis series: mental ray

In this series, we take you through some of the different render engines that are out there. There are plenty of them, all with their perks and downsides. This series explores Arnold, V-Ray, mental ray, and Redshift – all for Maya 2017. The lighting set up will be the same, and we’ll see if it’s possible to get the same results.
In this scene, our Render Wrangler Iris will use a HDRI for the overall lighting, four lights at the doors to mimic strong light falling through the door openings, and some extra small lights to highlight details or to light up the overall scene.

Good ‘ol mental ray. It has been around for quite some years now, and was created by Mental Images and later bought by NVIDIA at around the end of 2007. When I was in school, this was the programme that I learned on. mental ray is based on the ray trace system to create images, and mental ray has been implemented in most 3d software (Maya, 3dsMax, Autocad, C4D, Revit, Houdini, Softimage and Solidworks). mental ray has loads of settings that you can tweak, or mess up your render with horribly.

So let’s get going! We’re going to be using mental ray

Starting with the basics, we’ll start with some IBL and four arealights in the door openings like we have also done for the other two render engines. On the IBL I have set the Quality to 2 so we can get a bit more light details out of it.  Before we go to the first render, on the Arealights, set the Decay to Linear. You may choose to go for Quadric, but I prefer Linear, as it creates light that behaves as it would in nature. Don’t forget to tick use light shape in the mental ray menu of your lights. Now let’s try a render and see what we get.

mentalray 3D render of a barn

What immediately stands out is that the render time at this point is already over six minutes – and there is still a lot of grain. If the render time was super quick I wouldn’t be bothered, but we need to deal with this now. In the arealight, under the mental ray settings, go to area light and use light shape. Here you can set the samples. This reduces the grain as it is blasting out more light samples to be calculated.

At first, the test renders were rendering in a reasonably ok-ish render time but I have turned final gather on and upped my lights a bit more, and I have now entered the Valley of Boredom. My goodness this is taking for ever, and I am only rendering in 50% resolution! This is when I start to tell the office about my memories of naps in between renders, and I start to calculate how much time of my life I have actually wasted staring at a rendering screen.

After 8.14 minutes, my render is done on a 480×270 size. I dread the moment I need to render in full size. As I really do not want to waste my life waiting on renders to be done, I am going to have a look in my settings and see if I can lower some values. But don’t fret: on the final render, we will crank them up again if we need them. The biggest culprit is the quality of the IBL. When I put it back to 1 it more than halves the render times, and we can raise it for the final render just to help clear some of the grain. But instead of that, we might try adding a few more samples on our lights and see what is more efficient. Turn on final gather for the final render, as this optimized the light and the render time.

mentalray render of a barn

As you can tell, render times shoot up when you have one small thing not set correctly, and this is what frustrates me the most with mental ray. There are so many places where you can alter things, which is great if you understand what every single one of them does, but if you are a beginner with lighting it will be very confusing. The other side of the coin is that you can influence almost everything in the scene and work very specific with the lights. It all depends on how comfortable you are with a million settings…

mentalray 3D render of a barn

What do you think of the way that we lit and rendered this still? Do you find mental ray more confusing than reversing around a corner up a hill in your driving test? Worried that you’ll get yourself tangled, or up for the challenge?? Make sure you read our results to see which render engine is best for you!



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