Arnold 6 CPU vs GPU part 1

General / 28 December 2019

I’ve start test Houdini 18 and Arnold 6. first test was simple splines rendering, 250.000 splines instanced 25 times. it loads a 140MB alembic file.

rendered in 6 core Xeon CPU and Nvidia Quadro RTX 5000. (windows 10 pro)

the startup for Arnold GPU is slow, it renders faster, so its seems but for clear up the final image it takes for forever or just dropped /crashed, hard to tell on the GPU. the CPU is quite fast but much slower then GPU if it ever would finish. (adaptive sampling was on)

As soon as Arnold finish rendering the scene, it stops and do not refresh any more on parameter changes. so far i am not impressed with the arnold GPU rendering.

here the same scene Arnold CPU with only direct Lighting. (on my macbook)

some test with Arnold GPU. it performed much better with just direct lighting.

Abstract Renderman test in Houdini

General / 27 December 2019

I've open a Houdini and rendered with RenderMan 22.6.  I used only xrDirectLighting integrator and the render speed was super fast on CPU. I've ditched the Pathertracer for this scene, it gave no visual benefits/improvement in this case. Pure spline rendering, no Polygon meshes.





atmossphere volume in arnold

General / 27 December 2019

rendered with Arnold in Houdini. I've tried the atmosphere volumes the first time. easy to setup. The render time was quite slow on the volumes, typically for volumes, but much faster then render the screen environment with VDB cloud. I've used a mesh light for inner character illumination. 

it's a shame I could not use Arnold 6 GPU, because of its missing features. Volumes would boost get huge speed boost with volume raymarching on a GPU. I had to use a denoiser from Affinity Photo in dark areas.




fractal erode

General / 19 December 2019

Another test with Octane in Houdini. The render time was about 2:20 Minutes on RTX5000 for the image (in 5k resolution).

Sand eroding in octane with arnold

General / 17 December 2019

finally, I got some time to play with octane in Houdini. I am impressed with the interactivity of the renderer. The render time was about 2:30 Minutes on RTX5000 for each image (in 5k resolution). 




sand erode in octane with arnold

General / 17 December 2019

finally, I got some time to play with octane in Houdini. I am impressed with the interactivity of the renderer. The render time was about 2:30 Minutes on RTX5000 for the image (in 5k resolution).

light simulation

General / 09 October 2019

I’ve made a simple scene to test the physics of light. for proper light calculation, I used spectral render Indigo and Octane.

Indigo has multiple Engines, standard Spectral Path tracer on CPU or GPU and Bidirectional path tracing with MTL sampling (metropolis Light Transport). Octane has only default Spectral Path tracer on GPU but includes an MTL sampling method. I’v also added Renderman 23 to the test with its unified rendering integrator. It supports bidirectional path, manifold caustics and path guiding on the CPU.  

Another render engine like Arnold or Cycles with regular Path tracing would impractical fro complex light calculation tasks.

The base scene is Sphere and squashed Sphere underneath inside a volume box (uniform VDB).      

The following image is the result of Indigo Renderer with BiDirectional path tracing and MTL. It was by far the fastest rendering.

houdini logo

General / 03 October 2019

this quick and dirty 1-2 hour dash to create a logo for the Vancouver Houdini Usergroup. rendered in renderman 22.5

some Affinity photo adjustments:

About Render Engines part 2

Article / 29 September 2019

Each render algorithms has different benefit in different Scene / Light Situations.  Some common Render engines using following Algorithms:




Here is list Pro and Con based on my own Experience :   


Pathtracer

Pro :

  • easy to use
  • best for exteriors
  • great characters and outdoor renderings

Con :

  • bad for caustic
  • not so good for interiors with much indirect lighting and small light sources


BiDirectional Pathtracing

Pro :

  • very good for interiors
  • good and fast caustic 

Con :

  • not so fast for outdoor rendering
  • slow for reflected caustics


Spectral Rendering

Pro :

  • super easy to use
  • most correct physics 
  • mediun rendering
  • make use of physical correct modeling
  • great out of box image quality

Con :

  • slower rendering 
  • more memory use 32 floats instead 3
  • need physical correct materials
  • hard to get aov etc..
  • shader limitation


Metropolis Light Transport

Pro : 

  • faster for reflected caustic
  • excellent for caustic
  • best for interiors (indirect lighting, small light sources)

Con :

  • very slow for exteriors

Path Guiding

Pro :

  • extreme good for interiors (indirect lighting, small light sources)
  • much faster than PT for scenes with very difficult lighting (e.g. light coming through a small opening, lighting the scene indirectly)
  • fast caustics

Con :

  • not so fast for glossy materials
  • more setup time (tweaking render settings)
  • problems with detailed geometry

Biased Rendering

Pro :

  • fastest rendering
  • very useful for caustics + reflected caustics
  • most flexible render setups
  • great shader hacks

Con :

  • hard to setup
  • need knowledge if optimization algorithms
  • hard deal with large dataset
  • biased, artefacts, splotchy, low frequency noise
  • can have large memory footprint

stochastic progressive photon mapping

  • best for indoor
  • small memory footprint
  • handles all kinds of caustics robustly

About Render Engines part 1

Article / 25 September 2019

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).

image by Silverwing

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