CGI Environment Renders By Arpit Pandey

Biased vs Unbiased Rendering Engine

Hi Guys, My name is Arpit Pandey and I am a 3D Generalist & I want to talk about rendering. There are so many people out there struggling with 3D Renderings. So, I want to give out some Information that could hopefully get you guys up to speed and running.

SO, we have two types of Renderers :

  • Biased
  • UnBiased

Biased Render Engine:

What Biased Render Engine actually means is pre-computing a lot of information before sending out rays from the camera. In more simple words, It uses optimization algorithm to greatly speed up the render time but doing so It is not stictly just modelling the physics of light but it is giving an approximation.

Biased means “Limited”–and you set the limit.

Example of Biased Render Engine:

  • V-Ray
  • Redshift
  • Mental Ray
  • Render Man
  • Micropolygon

V-Ray is a pure raytracer, So everything is raytraced, and it is a hybrid renderer, using biased and unbiased both rendering methods.

Interior Render Using Vray by Arpit Pandey

Interior Render Using Vray by Arpit Pandey

Redshift uses approximation and interpolation techniques to achieve quality renders in a less amount of time than any other Unbiased render engine and the speed & quality of Redshift is quite amazing . The most Important feature of Redshift which is really amazing is that it lets you render massive scenes which may not even fit on the VRam of your video card.

Pro’s of Biased Render Engine:

  • More control
  • Superior render speed
  • You can predict the render times.

UnBiased Render Engine:

UnBiased Render Engine means that it has hard fact information that is being pushed through into the processor to figure out the information and a lot of cheating not occuring. To make it simple ” An UnBiased Render Engine take absolutely no shortcuts in its calculations of calculating rays.”

Unbiased render engines often produce exceptional render quality. Of course, the downside is that rendering speed is an issue.

The most of common misconception about unbiased rendering is that it is more physically accurate than biased rendering but the truth is both are inaccurate. Just the idea of using BRDF such as Blinn or GGX is in itself approximation of a real world Material.

Most of the film Industry uses UnBiased Render Engine.

Example of UnBiased Render Engine:

  • Arnold
  • Maxwell
  • Octane
  • Indigo
  • FStorm

Maxwell Renderer is, theoretically, the most accurate unbiased engine out there. It is more or less designed to simulate the physics behind an IRL camera.

V-Ray has a PPT (progressive path tracing) feature that somewhat simulates an unbiased renderer, but not quite, and there’s limitations on what kind of shading level you can achieve with it (so there’s a chance you won’t be able to render out a truly noise free image).

Thea Render has both biased and unbiased rendering engines, which all share the same material system. Thea is maybe 80% the renderer that Maxwell is. The fact that you can switch engines really easily and not have to retexture everything is pretty handy though.

FStorm is a new UnBiased GPU render engine that is developed by Andrey Kozlov. At the moment FStorm is only available for 3Ds Max, but other 3D softwares will be supported in the future. However FStorm shares a very interesting story with Octane as it was none other than Andrey Kozlov a.k.a Karba  who was previously known as a developer of Octane developed FStorm.  He was responsible for many of the most important features in Octane like displacement, bloom/glare, volumetric light/fog, QMC sampling, BRDF model and several others, and he was also responsible for the 3ds Max plugin. Rumor told that he had left the Octane team, Then suddenly, FStorm comes along like a lightning bolt from clear skies.

There are many other’s but I’ve never tried them. I only deal with V-Ray on a daily basis.

What is better? Biased or unbiased?

Most renderers use solutions that make their render biased, even if they call it unbiased. If they didn’t, the process would be extremely slow. Biased engines are very intelligent; in that they are the most efficient way of getting a correct image. In fact, you can almost call unbiased inefficient.

Long story short: if you are doing true scientific physical calculations and have a ton of computational power and time, unbiased may serve you well. If you are interested in rendering physically accurate images in a reasonable amount of time, biased solutions will get you there faster. Chances are you are already doing this no matter what rendering engine you are using.

I hope this helps people choosing there own favorite Render Solutions.

Happy Rendering, Thank you.


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