Ambient Occlusion and Visibility difference in Softimage 2013 and Softimage 2012

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  10 October 2012
Ambient Occlusion and Visibility difference in Softimage 2013 and Softimage 2012


I would like to ask a question to the community. Unfortunately, I myself do not really do any real work with Softimage at all, but I need to investigate a problem, that is causing some issues for actual artists. So, please excuse me if my explanation is not too technical

The problem is regarding XSI 2013 and XSI 2012. Here are the steps and a screenshot of a simple setup I created as a way to show you what I mean, so that you can replicate them and tell me some information, if you know, about what might be a cause. All steps are the same for XSI 2013 and 2012.

1.) Once XSI is opened, under Model option do Primitive -> Polygon Mesh -> Sphere (sphere_1). Do it once again (sphere_2), but now in the opened pop-up make sphere_2's radius larger. Now you have an inner and outer spheres.

2.) Select outer sphere and do Material -> Constant. In the opened pop-up go to Transparency/Reflection, and under Mix color make RGB numbers equal to 1. Select inner sphere and do Material -> Constant.

3.) With the inner sphere selected, open up Render Tree and find Ambient Occlusion node. Add it to the tree and connect to Constant node to "color". Open up the node and make Maximum distance 6 (for me it was a good enough distance)

4.) Go Primitive -> Polygon Mesh -> Cube. Lower a cube such that it covers only half of the inner sphere.

5.) Open up explorer, select outer sphere and hide it.

6.) Now, in the explorer expand cube and open its Visibility node. In Rendering tab, there are two checkboxes to notice - under Ray Visibility -> Secondary, and under Shadow -> Caster.

7.) In 2012, if you have both check-boxes checked, a lower part of the sphere will be darker. If Secondary check-box is unchecked, it is not.

8.) In 2013, Secondary check-box has no effect. Using Caster though, it has the same effect as Secondary check-box in 2012.

That is, in 2012 and 2013 those check-boxes exchanged their effects. In 2012, Caster has no effect on that particular setup.

Can anyone give a reason? Work-around is obvious (just use appropriate check-boxes), but I want to know if it is a fix done in 2013, or the behavior is an actual bug?

I could not really find in changes to 2013 Softimage anything related to it, but such specific things are really hard to find, so maybe someone here knows about it.
  10 October 2012
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