# luminance values

Hello all,

I want to find the luminance values for a grid of points using rtrace but
from a specific position of an observer.

observer's position (2,0,1.5)

grid of points : (0,1,0) , (0,2,0)
(1,1,0) , (1,2,0)
(2,1,0) , (2,2,0)
(3,1,0) , (3,2,0)

How do I have to write the rtrace command and the file which contains the
points and the vectors?

Thanks,

Nick

Hi Patrick,

If you put your grid points in a file called 'grid.pts' you can use the
following rcalc command to generate a file containing a series of
directions from the observer point to each grid point.

rcalc -e '\$1=2;\$2=0;\$3=5;\$4=\$1-2;\$5=\$2-0;\$6=\$3-1.5' grid.pts >
directions.pts

Then use rtrace as normal to calculate the luminance values using the
file directions.pts. Ore more simply you could pipe the results of rcalc
directly to rtrace like so:

rcalc -e '\$1=2;\$2=0;\$3=5;\$4=\$1-2;\$5=\$2-0;\$6=\$3-1.5' grid.pts | rtrace
...

By the way, your points need to be entered in the grid.pts without
commas or parenthesis like this:

0 1 0

0 2 0

1 1 0

Andrew

···

________________________________

From: [email protected]
[mailto:[email protected]] On Behalf Of
panick
Sent: 05 September 2007 17:22
To: [email protected]

Hello all,

I want to find the luminance values for a grid of points using rtrace
but from a specific position of an observer.

observer's position (2,0,1.5)

grid of points : (0,1,0) , (0,2,0)

(1,1,0) , (1,2,0)

(2,1,0) , (2,2,0)

(3,1,0) , (3,2,0)

How do I have to write the rtrace command and the file which contains
the points and the vectors?

Thanks,

Nick

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