POV-Ray : Newsgroups : povray.general : photon problem: image of projected image_map is clipped at the corners : photon problem: image of projected image_map is clipped at the corners Server Time
7 Dec 2022 09:20:06 EST (-0500)
  photon problem: image of projected image_map is clipped at the corners  
From: Corvin Zahn
Date: 20 Sep 2010 05:45:00
Message: <web.4c972bdffcc128eac947b6de0@news.povray.org>
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(tm) 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)

Does anyone have an idea, whats wrong?

Many thanks,
Corvin

PS: In the case of questions: I want to simulate a projection system with
mirrors, so I need photons. The offset of the slide in y direction is due to the
projector offset.


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