This is a quick overview of current render Engines for Houdini and General in terms of MotionGraphics and VFX usage.
There are different RenderEngines out there, each one is unique and uses different method to solve a problem. I am looking into Arnold, RenderMan, Vray, Octane and Redshift. For comparison reason I added Indigo Renderer engine.
There are different way to render a scene with benefits and shortcomings. lets start with most common one.
image by Glare Technology
Pathtracing (PT)
to be precise Backward Pathtracing. In backward ray tracing, an eye ray is created at the eye; it passes through the viewplane and on into the world. The first object the eye ray hits is the object that will be visible from that point of the viewplane. After the ray tracer allows that light ray to bounce around, it figures out the exact coloring and shading of that point in the viewplane and displays it on the corresponding pixel on the computer monitor screen. that’s classical way, which all of the Render engines uses as standard.
Metropolis light transport (MLT)
This procedure has the advantage, relative to bidirectional path tracing, that once a path has been found from light to eye, the algorithm can then explore nearby paths; thus difficult-to-find light paths can be explored more thoroughly with the same number of simulated photons. Metropolis light transport is an unbiased method that, in some cases (but not always), converges to a solution of the rendering equation faster than other unbiased algorithms such as path tracing or bidirectional path tracing. MetroPolis is often used in Bidirectional mode (BDMLT).
Path Guiding
Mix between Path-tracing and MLT, unbiased technique for intelligent light-path construction in path-tracing algorithms. Indirect Guiding that improves indirect lighting by sampling from the better lit or more important areas of the scene. goal is to allow path-tracing algorithms to iteratively “learn” how to construct high-energy light paths.
link to latest Siggraph paper
BiDirectional Pathtracing ( BDPT )
Regular backward Pathtracing has hard time in indoor scene with small light source because it take lot’s rays and bounce to find a tiny light in a room, just to see if a object gets light by the light.
with Bidirectional, rays are fired from both the camera and light sources. They are then joined together to create many complete light paths.
Spectral rendering
image by Silverwing
Unlike most renderers which work with RGB colours, Spectral renderers uses spectral colour throughout, from the physically-based sky model to the reflective and refractive properties of materials. The material models are completely based on the laws of physics.This makes it possible to render transparent materials like glass and water at the highest degree of realism.Spectral renderer are pretty good in simulate different medium atmospheric effects like under water or earth air atmosphere.
Biased Rendering
hat 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 an optimization algorithm to greatly speed up the render time but doing so It is not strictly just modeling the physics of light but it is giving an approximation
here is an example what Spectral rendering able to do:
Indigo renderer Planet-scale atmospheric simulation
Unlike other rendering systems which rely on so-called practical models based on approximations, Indigo’s sun and sky system is derived directly from physical principles. Using Rayleigh/Mie scattering and data sourced from NASA, Indigo’s atmospheric simulation is highly accurate. It’s stored with full spectral information, and allows fast rendering and real-time changes of sun position.
some examples of Atmosphere simulations by Indigo Forum user Yonosoy.
