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 refractive caustics

Software:
Maya 2018 | Arnold 5

An account of the drastic measures that need to be taken in order to ‘persuade’ Arnold for Maya to render refractive caustics.

  1. In the refractive object’s shape attributes,
    Under ‘Arnold’, ‘Opaque’ must remain checked.
    * This is unintuitive but when refractive caustics are calculated there is no need for transparent shadows. the caustics pattern is in fact the light refracting through the object.
  2. The refractive object’s aiStandardSurface shader must have it’s Transmission layer active.
    For a colored refractive object, Transmission Weight should be 1.0,
    A color should be selected, and the density of the color should be controlled with the Depth attribute (higher values make the color less dens).
    In the shader’s advance attributes, check ‘Caustics’.
    In the shader’s Specular layer, set the IOR to match your material.
    * The default of 1.52 is the IOR for glass, and water would be IOR 1.33 for example.
  3. For refractive caustics to be rendered, the light source must be an Arnold Mesh Light,
    And in its shape attributes, under Light Attributes ‘Light Visible’ must be checked.
  4. In many cases, in order for the caustics pattern’s intensity to be correct,
    The ‘Indirect Clamp Value’ must be raised in Render Settings > Arnold Renderer, under Clamping.
  5. In some cases the Transmission value under Ray Depth in Render Settings > Arnold Renderer must be increased for the caustics to render properly.
    * Light simulation must be able refract through all the relevant surfaces.
  6. To increase the caustics render quality, the number of Diffuse samples must be raised in Render Settings > Arnold Renderer.
    * This may be unintuitive, but the caustics pattern is actually part of the Diffuse rendering of the surface upon which the caustics are appearing.

That’s it!
Hope you find this useful 🙂

Arnold_Coustics_AArnold_Coustics_BArnold_Coustics_C

 

 

Simple Toon shader setup in Maya & Arnold

Software:
Maya 2018

Use a Surface Luminance node as a V coordinate input value for a Ramp (V Ramp) node containing the toon colors.

* Note that the Clamp node is important so results will be ass expected, it clamps the Surface Luminance values to 0.99 so the V coordinate will nor cycle back to the beginning of the Ramp.

Untitled-1.jpg

Related:
Toon Shading in V-Ray for Maya

Arnold for Maya Motion-Blur

Software:
Maya 2018 | Arnold 5

  1. In the Render Settings window, Arnold Renderer tab, under Motion Blur,
    Check ‘Enable’.
  2. Set the ‘Length’ attribute to set the Motion-Blur size.
    * the default length of 0.5 means the Motion-Blur will be calculated as a result of a photographic exposure duration of half of a frame duration, or 180 degrees in cinema camera terminology.
  3. Raise the number of Keys to accurately simulate Motion-Blur for very fast rotational motion like helicopter propellers and car wheels.

Untitled-2.jpg

Note:
To generate a Motion Vector (Velocity) AOV (also referred to as ‘Render Element’ or ‘Pass’), in order to add the Motion-Blur effect in a compositing software:

  1. The ‘motionvector’ AOV must be added to the AOVs list in the AOVs tab of the Render Settings window.
  2. Motion-Blur must be enabled in the Motion-Blur part of the Arnold Renderer tab in the Render Settings window.
    * Otherwise motion vectors will not be calculated.
  3. In the Diagnostics tab of the Render Settings window, under Feature Overrides, check ‘Ignore Motion Blur’, so Motion-Blur will not be rendered.

Untitled-2

Untitled-3

 

Related posts:

Arnold for Maya Depth of Field (DOF)

Saving multi-channel EXR file with Arnold for Maya

 

Saving multi-channel EXR with Arnold for maya

Software:
Maya 2018 | Arnold 5

  1. In the Render Settings > Common tab, choose EXR as the output file format.
  2. In the Render Settings > AOVs tab, open the drop-down menu on the right side of one of the AOVs in the list, and choose Select Driver.
    This will bring up the defaultArnoldDriver node Attributes.
  3. In the defaultArnoldDriver node Attributes, under Advanced Output, check Merge AOVs.

Untitled-4

Untitled-3

 

Rendering an animation in Maya and Arnold

Software:
Maya 2018 | Arnold 5

  1. Set a Project Folder or Image output path.
  2. In the Render Settings > Common tab, set the output file format, and in Metadata, set Frame/Animation ext. select an option that isn’t Single Frame.
    * This will make the Frame Range settings available.
  3. Set the Frame Range.
  4. Set the Maya UI to Rendering and choose Render > Render Sequence.

Untitled-1

Untitled-2