Wednesday, June 10, 2015

Revit 2016 - Rendering Engines

Some years ago we went through a changeover from Accurender to Mental Ray as Autodesk focused on Mental Ray as their preferred rendering engine for several of their products. If you didn't know it already Mental Ray belongs to Nvidia. Autodesk has purchased companies, and their products, more recently that allows them to focus on using what is now their own rendering engine; which is being called Raytracer. Don’t confuse it with the Visual Style called Raytrace.

This means we find ourselves in another period of rendering engine transition from Mental Ray to Autodesk Raytracer instead. Revit 2016 has both Mental Ray and Autodesk Raytracer options available to us when we decide to render via our desktop (not using Cloud Rendering).

As I understand it they are motivated to go through this in order to provide what they believe will be simpler yet higher quality and faster rendering options because they will have more control over the engine being used; it’s theirs, not someone else’s. Unfortunately it takes quite some time to plug in and unplug something so intrinsic to how Revit works. I believe that, if things go according to plan, we’ll probably just find the one option (Raytracer) in the next full release of Revit.

Considering the visualization products available today like Revizto, Lumion, Fuzor and Enscape, which all offer a very impressive real time rendering environment as well as integrating well with Revit, I can’t help but wonder if the development team is really in tune with the market. Maybe they have something up their sleeves we just can’t see yet? I hope so. For a very basic comparison I took a model I made recently during a training session and used both rendering engines with just exterior lighting. I used the same location each time, southern CA (where I live).

This is using Mental Ray (3:27 seconds at Medium)

This is using Raytracer (2:53 at medium)

This time I switched to rending the same model and view using the Draft setting. This is using Mental Ray (51 seconds at Draft)

This time using Raytracer (39 seconds at draft)

For each rendering Raytracer was the faster engine. The quality difference between the draft renderings was much more noticeable with Raytracer’s result being cleaner and clearer. Raytracer’s Draft and Medium was much more consistent than for Mental Ray. If rendering is your passion then I encourage you to read Daniel Stine’s article about this new development in Revit. It was published at AECBytes.

A quirky outcome of this transition is how the two engines deal with the Adjust Exposure feature.

With Mental Ray we can render and then click Adjust Exposure and tweak the result, seeing the changes in the image immediately. With Raytracer we can't do that. We CAN use Adjust Exposure first and then render, which makes no sense to me at all. This means we have to render first, make some adjustments to the exposure (which is adjusting blindly), render again to see if it provides a better result...repeat.

It's my understanding that it is what it is...for now...


Aaron Maller said...

Woah. That's unfortunate. I hadn't noticed yet that Adjust Exposure doesn't work post-render. I guess that means exporting and using Office Photo Editor or Photoshop for post processing, again. That's effing annoying.

Why time was spent on a rendering engine that is still 100% CPU based is a total mind-f**k. Why would anyone do that with the state of GPU cards? Oh, because they want us to render in the cloud. Right.

Alex Page said...

Also - its a known bug that the new Raytracer doesnt work with a lot of IES files. So I don't use it at all untill that is fixed since all the light I make have IES files attached: means that the renders just look better :)