Christoph Hormann wrote:

 >What you see on the front face of the box are exactly the explained 
 >shadow ray noise effects you also see on Wolfgang's samples caused by 
 >tangential lighting.  The surface is always found reliably, just if it 
 >is in shadow or not varies.  Since these surfaces result from a 
 >precisely linear function the linear interpolation leads to perfect 
 >results here for arbitrary accuracy values (on the faces, not near the 
 >edges and only within the accuracy of floating point numbers of >course).

 >Since you usually won't use tangential lighting in real scenes for 
such >flat surfaces i moved the light source a bit.


Umm, I see this a lot, actually. The more complex a shape becomes, the 
more these 'tangental lighting' artifacts appear. They happen on curved 
surfaces, too, but with less obvious striation. I hate having to move my 
light_source so often, but at least it's a fix for the flat surfaces...

 >I also changed max_gradient to 4 (the real maximum gradient of the 
 >function seems just above 3).  Here are the results:

 >no interpolation:

 >http://www.tu-bs.de/~y0013390/files/sam_test1_o05.png
 >http://www.tu-bs.de/~y0013390/files/sam_test1_o01.png
 >http://www.tu-bs.de/~y0013390/files/sam_test1_o001.png

 >with Wolfgang's patch:

 >http://www.tu-bs.de/~y0013390/files/sam_test1_i05.png
 >http://www.tu-bs.de/~y0013390/files/sam_test1_i01.png
 >http://www.tu-bs.de/~y0013390/files/sam_test1_i001.png

 >Christoph


Wow. Those results look encouraging. It's much like I suspected: edges 
no longer have that jagged look. The chopped-up surface is now smooth. 
Some spots still appear, though. I'm sure in time all such artifacts 
will be resolved.

Have you tried both patches (yours and Wolfgang's) combined yet? With AA?


-Sam

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