Arnold for Maya – Transmission Scattering (Ray Traced SSS)

Software:
Maya 2018 | Arnold 5

Scatter

The Arnold Standard Surface Shader’s Transmission Scattering options can be used for simulating highly realistic volumetrically ray-traced sub-surface-scattering suitable for materials like wax, soap, milk etc.

While the Transmission Depth attribute controls volumetric light absorption within the object (fog), the Scatter attribute controls what percentage of the light will be scattered instead of absorbed, effectively creating the murky effect of semi-transparent materials.

Note that for the scattering effect to work Scatter must have a dominant percentage value, and the Depth attribute must generally be much lower (shallower) than what would create coloring without scattering, otherwise the object will continue to look transparent and lacking the internal substance that we want to simulate.

Also note that the Opaque attribute must be unchecked in the Arnold attributes of the object’s shape node for the light to be able to pass into the mesh and illuminate the volume.
*This is actually a “cheat”, because physical semi-transparency has to be simulated by indirect light calculation or caustics, but for dense volumes like wax it’s very effective and the loss of realism is insignificant.

Untitled-1

Untitled-2.jpg

You can simulate the effect more accurately by rendering caustics,
In that case the Opaque attribute in the Arnold attributes of the object’s shape node must be checked and more steps must be taken allow refractive caustics to be ray-traced.

Note that simulating the effect using caustics will be very demanding in Transmission samples and Ray Depth.

Scatter_Caustics

Related:
Translucency

Advertisements

Using Arnold’s Ambient Occlusion node to create an eroding paint shader effect

Software:
Maya 2018 | Arnold 5

Arnold’s Ambient Occlusion (dirt) node can be used as a procedural mask to create interesting material effects like in this example of paint that is eroded at the model’s bulging areas to reveal metal beneath it.

In this shader’s case the Ambient Occlusion node is connected to the Mix property of an Arnold Mix shader, that blends between two different Arnold Standard Surface shaders, one simulating the underlying tin metal, and the other simulating the red paint that covers it.

Note that in the Ambient Occlusion node the Invert Normals property is checked, so that the effect will create a mask for the bulges and not for the creases,
And also that the Self Only property is checked so that the node will behave as a fixed object mask disregarding the proximity of other objects.
In this example the output of the Ambient Occlusion node is also process using a Remap Value node to increase it’s contrast so it will define borders between the areas.

Paint-Metal.jpeg

Untitled-1.jpg

Untitled-1

Arnold for Maya Depth of Field (DOF)

Software:
Maya 2018 | Arnold 5

Untitled-2.jpg

  1. In the camera shape node’s Arnold Attributes:
    Check ‘Enable DOF’.
  2. Set ‘Aperture Size’ and ‘Focus Distance’ to control the effect.
    Note:
    The Aperture Size attribute isn’t an f-number aperture like we would expect in photography but a radius in world units.
    Larger Aperture Size values (larger lens Iris opening), and shorter Focus Distances will cause a narrower Depth of Field which will result in the background appearing more blurry.
    DOF is generally more apparent with ‘long lenses’ (shorter focal length).
  3. Set other Aperture attributes like the number of blades and aspect ration to further design the appearance of out of focus areas and especially highlights.
    * The optical effect referred by the term ‘Bokeh’ in photography.

 

Related Posts:

Arnold for Maya Motion-Blur

After Effects Camera Lens Blur

Arnold for Maya Standard Surface Shader Translucency / Paper Shader

Software:
Maya 2018 | Arnold 5

Translucent
In this example, the lamp shade has a Translucent material

The Subsurface component of the Arnold Standard Surface shader (aiStandardSurface) controls Sub Surface Scattering (SSS).
When the ‘Thin Walled’ option is checked in the Geometry attributes of the shader, the Subsurface isn’t rendered as a full volume of material like soap or skin/flesh (the effect that is traditionally called Subsurface Scattering – SSS) but as a thin paper-like translucent surface like paper, thin cloth thin leaves, lamp shades etc. (the effect traditionally called Translucency or ‘Paper Shader’)

* Note that this option is suitable mainly for polygon surfaces without thickness (just one side)

Untitled-1

To create a Translucent shader with Arnold:

Subsurface Weight must be higher than 0.0 for the effect to be computed.

In Geometry, check Thin Walled for the SSS to be rendered as Translucency (Paper Shader).

Extra options:

Use samplerInfo Node Facing Ratio output in Subsurface weight to add realism by changing the weight by angle.

Multiply weave texture with Facing Ratio to simulate fabric translucency.

Untitled-3.jpg

Arnold renderer – First impressions

Software:
Maya 2018 | Arnold 5

As a 3D rendering instructor I’ve been recently required to get familiar with rendering animations using Arnold for Maya so that I’ll be able to train VFX / Animation students to do so.

So today, after about 15 years since the last time I worked with Maya, I installed the latest version of the software’s educational edition on my PC, and started finding my way around the basics, and rendering with the Arnold renderer.

So obviously, the Arnold renderer is a state of the art production ray-tracer for the film VFX industry, and it sure feels that way with its no-nonsense super-realistic uncompromising physical approach to all the aspects of rendering, giving the artist total freedom to configure whatever he or she can possibly want,
And for someone with an understanding of physical definitions of light sources, optical attributes of surfaces, physical shaders and the technical process of ray-tracing, it’s an absolute joy to use.

So what’s the problem?

The problem is that the Arnold renderer wasn’t developed as a practical rendering solution for independent artists relaying on one or two PC CPU’s as the main rendering work force.
Arnold’s Brute Force rendering approach is very convenient to use and provides awesome shading quality, but it requires massive processing power to be practical in production of animations, even with today’s multicore desktop CPU revolution that was started with AMD launching the Ryzen chips.

* I must admit that (in the field of 3D visualization) I got spoiled by using Mental Ray and V-Ray over the years and got used to rendering with at least 3 bounces of indirect diffuse illumination,
Something that using interpolated GI calculations like irradiance caching and such can be done relatively fast on a desktop PC, but using accurate Brute Force to do it (on a desktop PC CPU) makes it impractically too slow.

The good news:

A) The GPU rendering revolution that was enabled by the nVidia Cuda technology is making massively parallel Brute Force rendering practical at a fraction of the price of CPU processing power.
Example:
About 3 years ago I decided I must check what’s this “Cuda rendering” all about, so I purchased a Geforce Gtx Titan Black GPU (Geforce 7 series) for about 1200$.
That GPU had Brute Force rendering power equivalent to about 16 3Ghz CPU cores.
Today you can get the same speed and memory with a 300$ Geforce Gtx 1060 GPU.
But Arnold isn’t a GPU renderer.. one may rightfully say….
* It should be said that GPU rendering is currently limited in the amount of memory compared to CPU rendering, and also OSL shaders are not supported.

B) Cycles renderer, Blender’s own built-in render engine is a GPU renderer, and it’s very similar to Arnold in its highly physical no-nonsense Brute Force rendering approach.
So if you wish to enjoy an “Arnold Style” physical shading and Brute Force rendering workflow in a small indie studio environment, GPU rendering with Blender and Cycles is a good way to do that, plus the software is free.
A relatively modest investment in 2 Geforce Gtx 1070 GPUs will give you Brute force rendering power roughly equivalent to 40 3Ghz CPU cores, at about a 4th or a 5th of the price it would cost in CPU’s.

All that being said..
Arnold is absolutely awesome! 😀

Update:
It seam that a version of Arnold that can render on GPU is on it’s way, and this is great news!