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#92 - Sphere_Sweep Bug

Attached to Project: POV-Ray
Opened by Jeff Wood (Woody) - Thursday, 01 April 2010, 00:40 GMT
Last edited by Christoph Lipka (clipka) - Saturday, 19 June 2010, 01:13 GMT
Task Type Definite Bug
Category Backend → Geometric Primitives
Status Closed
Assigned To Christoph Lipka (clipka)
Operating System Windows XP
Severity High
Priority High
Reported Version 3.70 beta 36
Due in Version 3.70 beta 37
Due Date Undecided
Percent Complete 100%
Votes 0
Private No


This item may need to be merged with item FS#81. This is another sphere sweep bug, though they are of different spline types.

The code is

#include "colors.inc"

camera {
  location  <0, 0.0, -4.0>
  direction 1.5*z
  right     x*image_width/image_height
  look_at   <0.0, 0.0,  0.0>

light_source {
  <0, 0, 0>            // light's position (translated below)
  color rgb <1, 1, 1>  // light's color
  translate <-30, 30, -30>

#declare i_start = 0;
#declare i_stop = 3;
#declare i_step = 0.05;
#declare i_inc = i_start;
sphere_sweep {
  linear_spline                 // linear curve

  (i_stop - i_start)/i_step + 1,    // number of specified sphere positions
  #declare y_coor = 0.23*sin(7.1*i_inc);
  <i_inc, y_coor, 0>, 0.05
        #declare i_inc = i_inc + i_step;

pigment{color Orange}


This task depends upon

Closed by  Christoph Lipka (clipka)
Saturday, 19 June 2010, 01:13 GMT
Reason for closing:  Fixed
Additional comments about closing:  No beta tester feedback for way over a month now; I consider that good news.
Comment by Jeff Wood (Woody) - Thursday, 01 April 2010, 00:49 GMT

Sorry, posted wrong category. Also, did not know how to display image.

Comment by Christoph Lipka (clipka) - Monday, 19 April 2010, 07:49 GMT
  • Field changed: Status (New → Investigating)
  • Field changed: Percent Complete (0% → 50%)
  • Task assigned to Christoph Lipka (clipka)

Under some circumstances (apparently when the camera is close to the plane perpendicular to the spline, and sufficiently far away), the coefficients of the quadratic polynom to solve grow seriously small, causing some approximation mechanism in the root solver to kick in where it’s not helpful.

The issue seems easy to fix, but I’m not sure yet whether to modify only the spline code or the root solver as such (the latter will obviously affect other geometry for good or for bad).

Comment by Christoph Lipka (clipka) - Monday, 19 April 2010, 14:29 GMT
  • Field changed: Status (Investigating → Requires testing)
  • Field changed: Due in Version (Undecided → 3.70 beta 37)
  • Field changed: Percent Complete (50% → 100%)

fixed with change #4944.