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IDProjectCategory  ascTask TypeReported InPrioritySeveritySummaryStatusProgressDue Date
 165 POV-RayPhotonsDefinite Bug3.6Very LowLow photon problem: image of projected image_map is clipped ...Closed
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Task Description

Hi,

I have a problem with photons. The following stripped down code simulates a
slide projector:


#include "colors.inc"
global_settings {
  #if (1)   // switch photons on/off
    photons { count 1000000 }
  #end
}
camera { location <0, 0, 200> sky<0,1,0> look_at <0,200,-200> angle 90 }
// projection screen
plane { z, -200 texture { pigment { White } finish{ diffuse 1 ambient 0.1} } }
// slide
polygon {
  5, <0,0,0>, <1,0,0>,<1,1,0>,<0,1,0>,<0,0,0>
  pigment { image_map {jpeg "s7_0.9_320.jpg" interpolate 2 filter all 1.0 } }
  translate <-0.5, 0.2, -0.3>
  photons { target refraction on reflection off collect off }
}
// projector lamp
light_source { <0, 0, 0>  color <1,1,1> }

——————————————-

A point light source projects through a image_map onto a screen.

Without photons the projected image is ok:
http://img838.imageshack.us/i/test4woph.png/

With photons the left and right bottom corners of the image will be clipped:
http://img101.imageshack.us/i/test4wph.png/

The size of clipped corners depends on the y-offset in the translate command.

The povray Version is:
Persistence of Vision™ Ray Tracer Version 3.6.1 (Debian (x86_64-linux-gnu-g+
+ 4.3.3 @ x86_64-pc-linux-gnu))
(the 3.7 beta has the same problem)

I posted this question in the general news group and got an answer by Christian Froeschlin,
who could reproduce the problem and suggested as workaround to divide the slide into small stripes

http://news.povray.org/povray.general/thread/%3Cweb.4c972bdffcc128eac947b6de0%40news.povray.org%3E/

This works, but doesn’t explain the problem.

Does anyone have an idea, whats wrong?

Many thanks,
Corvin

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