[Radiance-general] Getting number of pixels for fisheye view

[Lars O. Grobe]

So of course I ran into that problem of having perfectly black surfaces 
in my field of view. If ever anyone needs a way to get around this, here 
is my solution for now, using nothing but primitive text processing (and 
I am sure that the grep line could be written nicer):

N_PIXELS=`vwrays fisheye.hdr | grep -v -c "0.00000e+00 0.00000e+00 
0.00000e+00 0.00000e+00 0.00000e+00 0.00000e+00"`

So I feed my image (fisheye.hdr) into vwray, which will produce 
viewpoint/direction vectors for each pixel. For pixels that are outside 
the view, it writes out three times zero. Grep -c counts those, but grep 
-v -c counts the lines NOT containing the six zero expressions. And this 
is the number of pixels inside my image's view.

Maybe someone finds it useful one day.

CU Lars.