The Persistence of Vision Raytracer (POV-Ray).

This is the legacy Bug Tracking System for the POV-Ray project. Bugs listed here are being migrated to our github issue tracker. Please refer to that for new reports or updates to existing ones on this system.


FS#55 - Output_Alpha=on doesn't work as documented

Attached to Project: POV-Ray
Opened by Olaf Reinhold (yamo64) - Thursday, 03 September 2009, 07:17 GMT
Last edited by Christoph Lipka (clipka) - Friday, 26 March 2010, 16:53 GMT
Task Type Definite Bug
Category Frontend → Image format
Status Closed
Assigned To Christoph Lipka (clipka)
Operating System All
Severity Medium
Priority Normal
Reported Version 3.70 beta 32
Due in Version Undecided
Due Date Undecided
Percent Complete 100%
Votes 0
Private No


I have installed POV-Ray 3.7 beta 34 on Windows 7
The setting ‘Output_Alpha=on’ doesn’t work as documented. With this setting the Background appear black and the scene is transparent.

Check with this Code:

camera {
   location  <3, 3, -3>
   direction <0, 0, 2.9>
   look_at   <0, 0, 0>
   right 1.0*x
light_source { < 3, 3, -3> color red 1 green 1 blue 1 }
   <0,0,0> 0.8
   pigment {color rgb<1,1,0>}
      ambient 0.2
      diffuse 0.8

and with this ini file:

+W121 +H121
This task depends upon

Closed by  Christoph Lipka (clipka)
Friday, 26 March 2010, 16:53 GMT
Reason for closing:  Fixed
Additional comments about closing:  No feedback from beta testers for months, so probably "no news is good news"
Comment by Christoph Lipka (clipka) - Wednesday, 09 September 2009, 10:23 GMT
  • Field changed: Status (Unconfirmed → New)
  • Field changed: Operating System (Windows 7 → All)
  • Task assigned to Christoph Lipka (clipka)

Behavior is indeed different from 3.6.

As POV-Ray uses a transmit value with fully opaque defined as 0.0 and fully transparent defined as 1.0, but TGA format uses an alpha value with values defined the other way round, this needs to be corrected; apparently, in refactoring of the image data container to store alpha instead of transparency, this correction was duplicated, with the effect of cancelling it out.

Comment by Christoph Lipka (clipka) - Wednesday, 09 September 2009, 10:36 GMT
  • Field changed: Status (New → Requires testing)
  • Field changed: Percent Complete (0% → 100%)

fixed with change #4886