Rendering difference between 1.16 and 1.17

[Erick]

I was just playing around with a mirror prop, when I spotted a difference in the renders of version 1.16 to 1.17.

So the mirror it self has a frame around it. The mat zones are left-right bars and top-bottom bars. While the side bars seem to render fine, the lower part of top and bottom bars are rendering in two different shades, as if they're two parts.
This happened in version 1.17

(next post will have a picture of version 1.16)

[Erick]

Here's the same scene, rendered with 1.16
The top and bottom bars of the frame are good now.

What could have caused this?

[abstrax]

It's is possible that the vertex normals in this scene are stuffed. Maybe Paul (face_off) can check the orientation of the normals?

[face_off]

Does changing the rayepsilon makes the images the same?

The normals calculation has not changed between 1.16 and 1.17, but you can check by rendering with 1.16 and 1.17 with kernel = "deep_channel_kernel", "type" = "Geometric Normals".

Paul

[Erick]

Sorry for the late response ....
As suggested, I did three more tests.

Deep_chan. Geo.normals with 1.16a6 (just forgot to set the focus right)

[Erick]

Deep_chan. 1.17a4
Virtually no difference to the 1.16 render

[Erick]

And finally a 1.17 render with all image maps and bump and whatever pulled out. just a RGBspectrum node of 127/127/127

[roeland]

Can you also post the images using the "Shading Normals" mode? These are the ones used to calculate the shading. For objects like this, with hard edges, it should look the same as the geometric normals.

--
Roeland

[face_off]

The reason for the difference between 1.16 and 1.17 is that there was a bug fix in 1.17 for reflections which means the mirror frame surface "normals' are interpreted differently. The fix for your scene is to DISABLE SMOOTHING on the frame material (material "sides" and "Top_and_bottom". You really should turn OFF smoothing on all flat surfaces (ie. the walls), particularly if they have a very low polygon count (ie. 1 polygon for an entire wall surface).

[EDIT: Manual updated to reflect the above info - http://render.otoy.com/manuals/Poser/?page_id=210]

Paul

[Erick]

Setting "smooth" to "Disabled", for the frame, indeed solves the problem.
What an impact on little check or uncheck marker can have, hehe =)
Thanks so much for the help, Paul!

@roeland, here are 2 renders, showing the shading normals (1.17).
1st one is with smoothing enabled, 2nd one with smoothing disabled: