Hello,

POV-Ray 3.7 RC7 win64, Windows 8 Pro 64 bit.

While doing some testing I found the an issue with transparency mapping, 
radiosity, and a background sphere. I am not sure it is a bug.

Here is the basic scene: A sphere with a cap on top. The sphere is about 
8 units diameter. The cap is slightly larger but not too tight to give 
coincident surface problems. There is a HDR background on a 150 unit 
diameter sphere to provide illumination. There is also a single point 
light. Scene is rendered with radiosity. See picture below:

http://i.imgur.com/5dZ8qPn.png

Here is the scene archive with maps:

https://docs.google.com/file/d/0B0MYeki9vLYYRU1xNmoxb2paeFk/edit?usp=sharing

File -> Download to get the whole archive.

If I put a transparency map on the red cap it works as it should. No 
shadows from the transparent sections. Only the letters cast a shadow on 
the blue sphere. See image below:

http://i.imgur.com/1wnnBqR.png

Sometimes I like the background scene for illumination but not as a 
background image. So I usually turn off its visibility by using the 
no_image flag on the background sphere. By turning off the image flag 
the transparent areas on the cap now cast an unexpected radiosity shadow 
on the blue sphere. Nothing else was changed. See render below:

http://i.imgur.com/l4RkMnG.png

This happens with all the radiosity settings I tried.

I can work around this by making the lighting sphere the largest and 
covering it with another smaller sphere that has the background I want 
with the no_radiosity flag on.

I do not know if this is a bug but I thought I mentioned here because of 
the unexpected results.


FlyerX

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