Rendering a world position pass with Arnold

You can use the Arnold_Point AOV to create a world position pass (an AOV is the Arnold equivalent of a render channel). Here’s the Arnold_Point render channel in the render region:

A world position pass (aka a position map), is an image where each pixel’s R, G, B colour values represent the x, y, z coordinates of the corresponding vertex, in 3D world space.

If you loaded the rendered position map into the FxTree, or Composite, you can see that the RGB values correspond to the XYZ position coordinates:



Arnold – Rendering shapes distributed along strands

Arnold always renders shapes as if they were lofted along the strand. It doesn’t matter whether you clear the Loft Shape along Strand checkbox in the Create Strands PPG, the shape will always be lofted in the render, like this:

If you want your instance shapes to be distributed along the strands, you could use a second point cloud to put the shapes along the StrandPositions:

If you find this slows down your viewport, change the Particle Display to points.

Glossy reflections in the Arnold standard shader

In the Arnold standard shader, you use specular reflections when you want glossy reflections. There’s direct specular (the “classical” specular hightlight) and indirect specular (glossy/blurry reflections), and both are part of the same BRDF behaviour. In this screenshot, direct specular (Direct Scale) is turned off, so you see only the indirect specular reflections. The Roughness makes those reflections glossy.

So what’s up with the separate Reflection/Refraction tab? Well, that tab gives you an alternate way to do sharp, mirror reflections (with no blurring or glossiness). However, with Specular, you can get pretty much the same thing by setting the Roughness to 0:

Finally, since I mentioned the direct specular, here’s the shaderball with just the direct spec:

Tip – UI color widgets have a visual cue for gamma correction

In the Display > Color Management preferences, you can turn on gamma correction for UI widgets like the color chip. On the PPG, there’s a visual cue (a “dotted highlight”) that tells you whether gamma correction is on.

Gamma-corrected color widget:


Regular color widget (no gamma correction):


Also, you can right-click the color chip to toggle gamma correction on and off for that specific widget.

This is all in the docs, but I have to admit I found that out only after I noticed this on my own. Too bad, because if I had known this, I would have figured out sooner why my color chips looked so “faded”:


(because at some unknown point in time I had enabled the display of gamma correction for UI widgets, and then set the Profile Source to “From LUT File”)

This week in video

A round-up of some of the Softimage videos posted this past week.

emTools 1.33 – Walk Through New Stuff

ICE Node for reading images at given UV coordinates

compositing images in ICE!

Manipulating colour in images

Psyop Softimage ICE Workshops

ICE-Rope-Rig (with Dynamic Controler Count and nice SubdivisionInterpolation)

Secondary deformations in Ice

Maxscript Modifiers VS Softimage Ice

Softimage – A guide to better reflections

Setting up Softimage for network rendering

I get asked this question from time to time. It’s actually pretty straightforward to set up…it’s managing the render jobs that may take more effort.

  1. On each render node, install a network-licensed version of Softimage.
  2. During the install, on the Product Information page:

    • Choose Network License.
    • Enter your serial number and the product key 590D1.
    • Enter the name of the license server computer.

Done. It’s all set up now, but there’s a few things you should check/consider:

  • Check that you can run xsibatch on the render nodes and get a license.
    If you have any problems, here’s some troubleshooting tips for xsibatch licensing.
  • Xsibatch needs to have read/write access to wherever you store your Softimage scene files and projects, and wherever you decided to output the rendered images.
    For example, you could have a separate file server for scenes and render output, or it could be the local workstation where you run Softimage.
  • Third-party addons, plugins, and shaders need to be available to the render nodes, either via a shared workstation or by installing them on the render node.
    Note that the user account used to run xsibatch will have a Softimage user folder on the render node.
  • You need a way to manage the render jobs that run on the render nodes. There are a range of possible ways to do this:
    • Manually starting xsibatch on each render node.
      You could either specify specific framesets to render, or use the –skip flag to tell xsibatch to skip frames that are already rendered [by other render nodes]
      For example:

      xsibatch –render “//server/project/scenes/Example.scn” –frames 1-10
      xsibatch –render “//server/project/scenes/Example.scn” –skip
    • Hand-rolling your own tools/scripts to start render jobs (for example, using pstools to start xsibatch jobs on the render nodes, or generating batch files to kick off render jobs)
    • Purchasing render management software (such as Royal Render—you may want to try the demo version)