POV-Ray

The following scene, showing an almost cylindrical cone floating above a plane, renders fine in POV 3.6.2, but is obviously broken in 3.7.0.beta.34:

camera {
  right     x
  up        y*image_height/image_width
  location  <80,50,40>
  look_at   <0,0,0>
}

light_source { <500,500,500> color rgb 1 }

cone {
  <0,0,30>, 11.303000, <0,0,-30>, 11.302999
  texture { pigment { color rgb 1 } }
}

plane { y, -20 texture { pigment { color rgb 0.3 } } }

The error occurs even with the -MB option, indicating that the problem has nothing to do with bounding, but is in the cone intersection testing code.

Cone is not on good place when first base point is lower then end cap point.
Example:

cone { <0, 0, 0>, 2, <0, 1, 0>, 1 } - good
cone { <0, 0, 0>, 1, <0, 1, 0>, 2 } - bad

This is on 3.7 beta 35 version.

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
#while(i_inc<=i_stop)
  
  #declare y_coor = 0.23*sin(7.1*i_inc);
  <i_inc, y_coor, 0>, 0.05
        #declare i_inc = i_inc + i_step;
 
        
#end

pigment{color Orange}

}

Thread safety issue in functions using splines. 3.7.0.RC7.

First vetting in p.bugreports where several users were able to reproduce the fail on the following systems:

1) Ubuntu 12.1 i7 920 using 3.7.0.RC7
2) Ubuntu 12.04, AMD 2431 CPU, Linux 3.2.0-45 kernel using 3.7.0.RC7 (g++ 4.6 @x86_64-unknown-linux-gnu)
3) POV-Ray 3.7.0.RC7 (icpc 13.1.0 @x86_64-unknown-linux-gnu)

 Intel(R) Xeon(R) CPU E5-2680 0 @ 2.70GHz

 uname -or
 2.6.32-279.14.1.el6.x86_64 GNU/Linux

 lsb_release -irc
 Distributor ID: CentOS
 Release:        6.3
 Codename:       Final

4) Confirmed with openSUSE 12.2.
5) Just to add to the system list: with Windows and a core i7 one yields the same result.
6) “Le_Forgeron” ran under Intel Inspector (XE 2013) and provided this feedback :

 ...
  that might be less than 60 seconds, but with Intel Inspector (XE 2013),
 it becomes 42:50 (just 14 data races, oh well, that's just so friendly).

 ID  Type Sources Modules State
 P1  Data race isosurf.cpp; mutex.hpp povray New
 P2  Data race mutex.hpp; povms.cpp povray New
 P3  Data race povray.cpp povray New
 P4  Data race povray.cpp povray New
 P5  Data race mutex.hpp; pov_mem.cpp; splines.cpp povray New
 P6  Data race mutex.hpp; pov_mem.cpp; splines.cpp povray New
 P7  Data race mutex.hpp; pov_mem.cpp; splines.cpp povray New
 P8  Data race recursive_mutex.hpp; scene.cpp; task.cpp; taskqueue.cpp;
 view.cpp povray New
 P9  Data race condition_variable.hpp; vfe.cpp; vfesession.cpp povray New
 P10  Data race condition_variable.hpp; unixconsole.cpp; vfesession.cpp
 povray New
 P11  Data race condition_variable.hpp; unixconsole.cpp; vfesession.cpp
 povray New
 P12  Data race unixconsole.cpp; vfesession.cpp; vfesession.h povray New
 P13  Data race unixconsole.cpp; vfesession.cpp povray New
 P14  Data race [Unknown]; unixconsole.cpp; vfesession.cpp
 libboost_thread.so.1.49.0; povray New

 Numbers 2, 3, 4, 8, 9, 10, 11, 12, 13 & 14 are related to the handling
 of session (and occur once or twice only, excepted #8, four times).

 Number 1 is about isosurface (adjusting gradient at isosurf.cpp:1099 vs
 1098 (testing its value), and copying the isosurface) (IMHO, rendering
 threads updating the object... not the best move without some
 atomic/protection (and not sure a DBL is/can be atomic)) (occurs 2505
 times).

 Number 5, 6 and 7 are about splines
 * sp->Cache_Type & Cache_Point, splines.cpp :803 vs :814/815 (2024 times)
 * sp->Cache_Valid, :805 vs :813 vs :904 (1770 times)
 * sp->Cache_Data, :807 vs :903 (5025 times)

 Only my 0.02¢ (yes, very cheap), but it seems to confirm

For test code see attached files or SplineThreadSafety.pov attachment to
p.bugreports and images were posted to p.b.images.

Issue shows up any time more than one thread is used. Use of AA tends to hide
the problem so do not use it if using the output image for testing.

Thanks.
Bill P.

Using trace or inside with a julia fractal causes a crash.

#declare Test = julia_fractal {
  <-0.083,0.0,-0.83,-0.025>
  quaternion
  cube 
  max_iteration 8
  precision 20
};
#declare Norm = <0,0,0>;
#declare Hit = trace(Test,<0,0,-10>,z,Norm);
#declare Center = inside(Test,<0,0,0>); 

It appears that reflective bounces from blobs are
not incrementing the trace level, causing self-
reflecting hall of mirror portions to stall renders.

in change #3319, csg got a new computation for its weighted textures.

But I’m confused by the computation of the weight: (circa end of csg.cpp file)

COLC weight = 1.0f / min(COLC(textures.size() - firstinserted), 1.0f);

I would have used a max() rather than a min().

It is transparent when there is only one texture, but:

• should there be no texture (an error...): it would be a division by 0
• should there be more than 1, the weight of each would be 1. which is without consequence UNLESS there is already some other textures in the list. The right value (from previous code) was 1/n

Or did I get a confusion about min() ?

min(0,1) == 0
min(4,1) == 1

Using max would protect against the division by 0 and the right value when multiple textures are used.

Any thought ?

UV-mapped textures for parametrics are broken in POV-Ray 3.70 RC3, in cases where two (or more) parametrics overlap in a scene.

In the following scene, note how the texture per se is always taken properly from whichever parametric is in front, while the UV coordinates are erroneously taken always from the red parametric where both overlap, no matter whether it is in front or back.

camera {
  location  <0.0, 1.5, -3.0>
  direction 1.5*z
  right     x*image_width/image_height
  look_at   0
}

light_source { <-30, 30, -30> color rgb 1 }

#declare Param = parametric {
  function { u*v*sin (15*v) },
  function { v },
  function { u*v*cos (15*v) }
  0, 1
  contained_by { box { -1,1 } }
  accuracy 0.002
  precompute 15 x,y,z
  rotate 180*x
  translate  <0.3,0.5,0>
}

object {
  Param
  uv_mapping
  texture {
    pigment {
      gradient x frequency 3
      color_map {
        [0 color red .5 ]
        [1 color red 1 ]
      }
    }
  }
}

object {
  Param
  uv_mapping
  texture {
    pigment {
      gradient x frequency 7
      color_map {
        [0 color green .5 ]
        [1 color green 1 ]
      }
    }
  }
  rotate y*180
}

POV-Ray 3.62 renders the scene properly.

As this bug has been found during code inspection, the uderlying cause has already been identified; I’m currently working on a fix.

Recently, I have been rendering an animation with POV-Ray 3.7 RC 6 using radiosity, photons and backside illumination. Many frames contained artefacts like in the attached image file. Trying to eliminate those artefacts I observed the following:

• Rendering the same frame several times did not reproduce the artefacts or reproduced them differently. I.e., when I rendered a second (third, fourth, ...) time with +SF100 +EF100, the black space in the image was somewhere else or in some cases disappeared.
• With radiosity turned off, no such artefacts have happened since, even in the scenes where they happened with radiosity turned on.
• Turning off photons with radiosity still turned on did not remove the artefacts.
• Rendering with one thread on one CPU core instead of two threads on two cores did not change anything except the rendering time.
• Changing the radiosity settings I have not tried thoroughly, but at least raising or lowering count or error_bound does not seem to have any effect on this.

While POV-Ray was rendering, no other memory-intensive or CPU-intensive programs were running and POV-Ray itself did not report any error (just the usual warnings that some of the used features could change in future versions etc.). Render priotity was set to “high”.

Due to a recent thread in povray.general (7th September 2013), I dive
into the code of height field creation.

There is 2 TODO in source/backend/support/imageutil.cpp, for
image_height_at() (circa line 512)

The first one is about using the index of palette-image: As far as *257
would indeed perform a better job to cover the full range than *256, it
would break backward compatibility with previous versions of povray (3.6
included) which only promoted the index as the Most significant byte,
keeping the least one at 0.

But on the second one, the new formula is plain wrong: (r*255+g)*255
should be (r*256+g)*255.
In previous versions, r*255 was the Most significant byte, and g*255 was
the least one.
Ergo, the value was r*255*256 + g*255, which can and should be only
factored as (r*256+g)*255;

I know it is damn late in the release schedule, but can that be either
be fixed before final official delivery or a memo added to the release
note that it would be fixed later and backward-bug will not be
maintained for that specific point (using rgb-8 or less bit per
channel-image for height field)

(it was not bugged in 3.6.1 nor before, it’s just that tiny little bit
of 3.7 that would should that bug)

If you look carefully at the attached pictures (povray +I... +H700 +W700 +A0.01) of scene and scene36, there is a significant difference at the top.
With 3.6, it matched exactly (hence the noise on the top pixels row) the view.
With 3.7, it cannot reach the top and leave a white area
(another difference is the slope on the side are also a bit more lower with 3.7, easier to spot when alternating the display of both pictures)

If you want to regenerate hf.png, it was rendered with povray 3.7RC7, +W400 +H400 +A0.01 +Ihf.pov

The white line at the bottom is expected, as the minimal value of the height field is “full green”

The following paraboloid renders correctly:

intersection
{ quadric { <1, 0, 1>, <0, 0, 0>, <0, 1, 0>, -1 }
  cylinder { 0, y, 1 }
}

However, when I extend the clipping cylinder downward:

intersection
{ quadric { <1, 0, 1>, <0, 0, 0>, <0, 1, 0>, -1 }
  cylinder { -y, y, 1 }
}

the object disappears completely in POV-Ray 3.7 and 3.7.1. In POV-Ray
3.6.1, it renders as expected.

POV-Ray 3.7.0.unofficial (self-compiled with g++ 4.8, but completely unaltered)
POV-Ray 3.7.1-alpha.8150025.unofficial
openSUSE 13.2 GNU/Linux

This scene file illustrates the problem:

// +w480 +h240
#version 3.6; //[sic]

global_settings { assumed_gamma 1 }

camera
{ location <0, 1, -7.5958>
  look_at <0, 1, 0>
  right 2 * x
  up y
  angle 43.1038
}

#default { finish { diffuse 0.6 ambient rgb 0.15618 } }

light_source
{ <-4.3125, 9.6250, -7.4695>,
  rgb 6856.3
  fade_power 2 fade_distance 0.10417
  spotlight point_at <0, 1, 0> radius 45 falloff 90
}

box
{ -<9, 11, 9>, <9, 11, 9>
  pigment { rgb 1 }
}

plane
{ y, 0
  pigment { checker rgb 0.05 rgb 1 }
}

intersection
{ quadric { <1, 0, 1>, <0, 0, 0>, <0, 1, 0>, -1 }
  cylinder { 0, y, 1 }
  pigment { green 0.5 }
  translate <-1.25, 1, 0>
}

intersection
{ quadric { <1, 0, 1>, <0, 0, 0>, <0, 1, 0>, -1 }
  cylinder { -y, y, 1 }
  pigment { green 0.5 }
  translate <1.25, 1, 0>
}

On the right side, there should have been a cylinder capped with a paraboloid. A thread has been started in povray.bugreports. Jerome has started to look at it.

Add a way to get and set font metrics.

Attached an image that shows what I’m talking about.

Thanks!!

Improve native support for 2D primitives. Ideally a 1:1 mapping of SVG primitives/shapes. They go a long way to making diagrams look a lot better. Having to create image maps based on externally created bitmaps slows the workflow down a lot!

There are various scripts around the Net meant for approximating things like isosurfaces and parametric objects using meshes. It would probably run bit faster and be easier to use if this were supported natively within Povray. The feature would require an additional object parameter in order to toggle this behavior on/off.

The text object isn’t working with /usr/share/fonts/truetype/freefont/FreeSans.ttf. Used to work - taken from an old .pov file of mine.

Rebuilt from
http://www.povray.org/redirect/www.povray.org/ftp/pub/povray/Official/Unix/povray-3.6.tar.bz2

$ povray +ifonttest.pov +ofonttest.png

Persistence of Vision™ Ray Tracer Version 3.6.1 (g++ 4.4.3 @
x86_64-unknown-linux-gnu)
This is an unofficial version compiled by:
darxus [at] chaosreignscom

.....

File: fonttest.pov Line: 8
Parse Warning: Character 101 (0×65) not found in /usr/share/fonts/truetype/freefont/FreeSans.ttf
File: fonttest.pov Line: 8
Parse Warning: Character 115 (0×73) not found in /usr/share/fonts/truetype/freefont/FreeSans.ttf

Verification that the problem is not in the .ttf file, this works (imagemagick):

convert -background lightblue -fill blue -pointsize 48 -font
/usr/share/fonts/truetype/freefont/FreeSans.ttf label:test fonttest.png

Problem verified when compiled from source on Ubuntu Lucid. Also exists in Ubuntu binaries from Lucid and Hardy.

Bounding box computation for CSG intersection appears to be broken when one member is an arbitrarily transformed plane.

// +W640 +H480 +MB1

#include "transforms.inc"

camera {
  location  <-0.2, 0.5, -4.0>
  direction 1.5*z
  right     x*image_width/image_height
  look_at   <0.0, 0.0,  0.0>
}

sky_sphere {
  pigment {
    gradient y
    color_map {
      [0.0 rgb <0.6,0.7,1.0>]
      [0.7 rgb <0.0,0.1,0.8>]
    }
  }
}

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

plane {
  y, -1
  pigment { color rgb <0.7,0.5,0.3> }
}

intersection {
  sphere {
    0.0, 1 }
  plane { -x, 0 transform { Shear_Trans(x,y+x*0.3,z) } }
  texture {
    pigment {
      radial
      frequency 8
      color_map {
        [0.00 color rgb <1.0,0.4,0.2> ]
        [0.33 color rgb <0.2,0.4,1.0> ]
        [0.66 color rgb <0.4,1.0,0.2> ]
        [1.00 color rgb <1.0,0.4,0.2> ]
      }
    }
    finish{
      specular 0.6
    }
  }
  rotate -y*5
}

polygon objects comprised of multiple “sub-polygons” don’t work properly if start/end points of sub-polygons do not exactly match, as can be demonstrated by the following code:

#default { texture { pigment { rgb 1 } finish { ambient 1.0} } }

camera {
  orthographic
  up 3.5*y
  right 3.5*x*image_width/image_height
  location  <0,0,-4>
  look_at   <0,0,0>
}

polygon { 8,
  // outer triangle
  0.70 * < cos(  0 *pi/180),sin(  0 *pi/180),0>
  0.70 * < cos(120 *pi/180),sin(120 *pi/180),0>
  0.70 * < cos(240 *pi/180),sin(240 *pi/180),0>
  0.70 * < cos(360 *pi/180),sin(360 *pi/180),0>

  // inner triangle
  0.35 * < cos(  0 *pi/180),sin(  0 *pi/180),0>
  0.35 * < cos(120 *pi/180),sin(120 *pi/180),0>
  0.35 * < cos(240 *pi/180),sin(240 *pi/180),0>
  0.35 * < cos(360 *pi/180),sin(360 *pi/180),0>
}

Note that the end points /should/ be identical. There are however some minor rounding differences, which mess up polygon computations. Compare with the following code, which leads to the desired results:

polygon { 8,
  // outer triangle
  0.70 * < cos(  0 *pi/180),sin(  0 *pi/180),0>
  0.70 * < cos(120 *pi/180),sin(120 *pi/180),0>
  0.70 * < cos(240 *pi/180),sin(240 *pi/180),0>
  0.70 * < cos(  0 *pi/180),sin(  0 *pi/180),0>

  // inner triangle
  0.35 * < cos(  0 *pi/180),sin(  0 *pi/180),0>
  0.35 * < cos(120 *pi/180),sin(120 *pi/180),0>
  0.35 * < cos(240 *pi/180),sin(240 *pi/180),0>
  0.35 * < cos(  0 *pi/180),sin(  0 *pi/180),0>
}

Code inspection shows that the polygon insideness testing code tests for precise equality of the points, whereas the general policy of POV-Ray is to accept slight rounding differences.

original post on povray.beta-test:

POV-Ray 3.7.0.RC3 on Slackware 13.0 x86_64.
I pointed povray to use the calibri.ttf font over on my Windows 7 partition.
The result is garbled - strange letters with accents appear instead of the
expected text. (KDE's kfontview opens calibri.ttf OK, with nothing strange).

Pointing povray to use other fonts of Win7, e.g. comic.ttf and arial.ttf, was
OK.

I solved the problem by pushing calibri.ttf through fontforge and resaving it
as mycalibri.ttf.

Cheers,
Peter

Confirmed with development version on Windows XP x64.

Possibly a similar problem as  FS#162 .

Thin tori exhibit artifacts in 3.7.0 RC3 when the camera is placed inside the torus close to its “center plane”, as can be demonstrated with the following scene:

camera {
  location  <0.0, 0.0, -0.5>
  direction 1.5*z
  right     x*image_width/image_height
  look_at   <0.0, 0.0,  0.0>
  angle 1
}

light_source { <-30, 30, -30> color rgb 1 }

torus {
  1, 0.001
  texture { pigment { color red 1 } }
}

From synthetic post of Cousin Ricky in p.beta-test, 2013-06-24 circa 3:19 pm (MST)

William F Pokorny anonymous@anonymous.org wrote:
> It seems to be the case the gradient warnings are only generated if the
> isosurface is naked. If it is wrapped in an object as was the case with
> my thread safety example, we get no warnings.

Confirmed. If only I still had the concentration required to investigate
computer code.

#version 3.7;

#ifndef (MG) #declare MG = 40/9; #end
#ifndef (Naked) #declare Naked = no; #end

global_settings
{ assumed_gamma 1
  radiosity {} //force isosurface calculations from all directions
}

light_source { <-3.3125, 7.6250, -5.7374>, rgb 1 }

camera
{ location <0.0000, 1.0000, -5.6713>
  look_at <-0.7969, 1.2000, -0.0598>
  angle 10.7447
}

#include "functions.inc"

#if (Naked)
  isosurface
  { function { f_sphere (x, 0, z, (2660 - 40*y) / 9) }
    contained_by { box { <-80, 31, -24>, <-128, 56, 24> } }
    max_gradient MG
    pigment { rgb <1, 0.75, 0> }
    scale 1/128
    rotate -35 * x
    translate y
  }
#else
  #declare Test = isosurface
  { function { f_sphere (x, 0, z, (2660 - 40*y) / 9) }
    contained_by { box { <-80, 31, -24>, <-128, 56, 24> } }
    max_gradient MG
    pigment { rgb <1, 0.75, 0> }
    scale 1/128
    rotate -35 * x
    translate y
  }
  object { Test }
#end

On the command line, try:

declare=MG=1 declare=Naked=1

and

declare=MG=1 declare=Naked=0

To lose the warning, I had to declare the isosurface. Just wrapping the naked
isosurface in an object{} generated a warning.

Further analysis

if((Stage == STAGE_SHUTDOWN) && (mginfo->refcnt == 0))

Blobs are currently limited to 1,000,000 components (with each cylindrical component counting as three: one cylinder + two end hemispheres); this limit may have served a historic purpose, but is now entirely arbitrary: The remaining code is limited only by the available RAM and the numeric limits of the int data type. The arbitrary maximum components limit per blob should therefore be removed.

Aside from unnecessarily limiting the power of the blob component, another drawback of the current test is that it is only performed after parsing of all the blob’s components, potentially hours after the limit had actually been reached.

As the following scene demonstrates, the “inverse” keyword produces unexpected results with quadrics.

Left: a sphere primitive as reference
Right: a sphere-shaped quadric primitive (sphere-shaped)

Top: plain
Bottom: inverse

The objects are clipped in half to better demonstrate the effect. Regular texture is shown in white, interior_texture in red; the surface normal of a selected point (blue) as returned by trace() is shown in green.

Note how the sphere’s surface normal, as well as the textures, are flipped when “inverse” is used (this is the intended standard behaviour of all objects), while the quadric’s normal and textures erroneously remain uchanged.

// +w800 +h600

#version 3.7;

global_settings{ assumed_gamma 1.0 }

#default{ finish { ambient 0.1 diffuse 0.9 specular 0.5 }} 

camera {
  perspective
  angle 40
  right     x*image_width/image_height
  location  <0,0,-10>
  look_at   <0,0,0>
}

light_source{ < 1000,3000,-3000> color rgb 1 }

background { color rgb 0.5 }

#declare T_White = texture { pigment { color rgb   1 } }
#declare T_Red   = texture { pigment { color red   1 } }
#declare T_Green = texture { pigment { color green 1 } }
#declare T_Blue  = texture { pigment { color blue  1 } }

#declare TopLeft     = sphere { 0, 1 }
#declare BottomLeft  = sphere { 0, 1 inverse }

#declare TopRight    = quadric { <1,1,1>, <0,0,0>, <0,0,0>, -1 }
#declare BottomRight = quadric { <1,1,1>, <0,0,0>, <0,0,0>, -1 inverse }

#macro Mac(Obj, P, D)
  union {
    #local N = <0,0,0>;
    #local O = <-0.6,0.4,-10>;
    #local Q = trace(Obj, O, D, N);
    #if (vlength(N) > 0)
      sphere { Q, 0.05 texture { T_Blue } }
      cylinder { Q, Q + N, 0.02 texture { T_Green } }
    #else
      cylinder { O, O + D*10000, 0.02 texture { T_Red } }
    #end
    object { Obj texture { T_White } interior_texture { T_Red } clipped_by { box { <-1,-1,-1>, <0,1,1> rotate y*30 } } }
    translate P
  }
#end

Mac(TopLeft,     <-1.2, 1.2, 0>, z)
Mac(TopRight,    < 1.2, 1.2, 0>, z)
Mac(BottomLeft,  <-1.2,-1.2, 0>, z)
Mac(BottomRight, < 1.2,-1.2, 0>, z)

As the following scene demonstrates, the “inverse” keyword produces unexpected results with fractals.

Left: a sphere primitive as reference
Right: a julia fractal

Top: plain
Bottom: inverse

The objects are clipped in half to better demonstrate the effect. Regular texture is shown in white, interior_texture in red; the surface normal of a selected point (blue) as returned by trace() is shown in green.

Note how the sphere’s surface normal, as well as the textures, are flipped when “inverse” is used (this is the intended standard behaviour of all objects), while the fractal’s normal and textures erroneously remain uchanged.

// +w800 +h600

#version 3.7;

global_settings{ assumed_gamma 1.0 }

#default{ finish { ambient 0.1 diffuse 0.9 specular 0.5 }} 

camera {
  perspective
  angle 40
  right     x*image_width/image_height
  location  <0,0,-10>
  look_at   <0,0,0>
}

light_source{ < 1000,3000,-3000> color rgb 1 }

background { color rgb 0.5 }

#declare T_White = texture { pigment { color rgb   1 } }
#declare T_Red   = texture { pigment { color red   1 } }
#declare T_Green = texture { pigment { color green 1 } }
#declare T_Blue  = texture { pigment { color blue  1 } }

#declare TopLeft     = sphere { 0, 1 }
#declare BottomLeft  = object { TopLeft inverse }

#declare TopRight    = julia_fractal{ <-0.083,0.0,-0.83,-0.025> quaternion sqr max_iteration 8 precision 20 scale 0.9 }
#declare BottomRight = object { TopRight inverse }

#macro Mac(Obj, P, D)
  union {
    #local N = <0,0,0>;
    #local O = <-0.6,0.4,-10>;
    #local Q = trace(Obj, O, D, N);
    #if (vlength(N) > 0)
      sphere { Q, 0.05 texture { T_Blue } }
      cylinder { Q, Q + N, 0.02 texture { T_Green } }
    #else
      cylinder { O, O + D*10000, 0.02 texture { T_Red } }
    #end
    object { Obj texture { T_White } interior_texture { T_Red } clipped_by { box { <-2,-2,-2>, <0,2,2> rotate y*30 } } }
    translate P
  }
#end

Mac(TopLeft,     <-1.2, 1.2, 0>, z)
Mac(TopRight,    < 1.2, 1.2, 0>, z)
Mac(BottomLeft,  <-1.2,-1.2, 0>, z)
Mac(BottomRight, < 1.2,-1.2, 0>, z)

Setting File_Gamma=1.0 produces unexpectedly bright output files for most output file formats, as if File_Gamma was set to 2.2 instead.

The underlying problem is a bug that, when File_Gamma is set to exactly 1.0, causes the encoding gamma function to be undefined, which was not meant to happen in current versions, and instead was reserved for future versions to signal that a file-format-specific default encoding gamma should be used. The image file output handlers already support this, most of them choosing the sRGB transfer function, giving roughly the same output as setting File_Gamma=2.2.

As a preliminary workaround, users may want to set File_Gamma=1.02 (any value smaller than 0.99 or greater than 1.01 should do).

Trying to build povray-3.6 against png-1.5 fails spectacularly.

.../include/png.h:666: error: forward declaration of ‘struct png_info_def’ png_pov.cpp:1405: error: invalid use of undefined type ‘struct png_info_def’

appears a lot in the output.

The problem is that png-1.5 hides structure members from public view.

Note, this is not the same problem as  FS#144 .

Versions of POV-Ray prior to 3.7 had the ability to write the image output as a stream to STDOUT. This was particularly useful in unix as it allowed POV-Ray output to be directly piped to other processes.

The introduction of SMP and the associated non-linear generation of pixels complicates stream output to the extent that it is not currently available in v3.7.

At a minimum 3.7 must at least be able to write the completed image to STDOUT after a render - this is not an optimal solution but is better than nothing. Ideally however once entire lines are complete (most likely this will occur in batches due to the block nature of the render subdivision) these lines will be written immediately to STDOUT (after possibly being processed through the appropriate image format routines).

NB currently the image format routines are not invoked until the entire render is completed, so to do this would be a significant modification. However if we limit real-time stream output to “simple” non-compressed formats (e.g. PPM), it would not be overly difficult, and from the point of view of Unix-like operating systems (where the piping feature is most useful), if the data is in PPM format it can easily be transformed into anything else.

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 }
sphere 
{
   <0,0,0> 0.8
   pigment {color rgb<1,1,0>}
   finish
   {
      ambient 0.2
      diffuse 0.8
   }
}

and with this ini file:

Input_File_Name=C:\Users\dfv_rei1\AppData\Local\Temp\Cuadrigula\PreviewObject.pov
Output_File_Name=C:\Users\dfv_rei1\AppData\Local\Temp\Cuadrigula\PreviewObject.tga
Output_File_Type=t
Output_Alpha=on
Bits_Per_Color=24
+W121 +H121
+a0.3
+q11
+a

source/png_pov.cpp included in povray-3.6.1 contains calls to an internal function of libpng (png_write_finish_row) which was removed from the public interface quite a while ago, so linking fails.

Also, in the 1.4 releases of libpng, the info_struct “trans” member was renamed to trans_alpha. This causes a compilation error in the same file.

A suggestion for the solution:
a) remove the png_write_finish_row prototype and function call
b) add something like:
#if PNG_LIBPNG_VER < 10400
#define trans_alpha trans
#endif
and change
cmap[index].Transmit = 255 - r_info_ptr→trans[index];
to
cmap[index].Transmit = 255 - r_info_ptr→trans_alpha[index];
(two occurrences).

There is a confirmed bug when writing jpg file format with the current linux build (beta39). when specifying +fj output format the following error occurs:

JPEG parameter struct mismatch: library thinks size is 372, caller
expects 376
JPEG parameter struct mismatch: library thinks size is 372, caller
expects 376
Render failed

this has been confirmed on ubuntu 10.4 and openSuSe 11.2 (assuming 32 bit version) as openSuSe 11.2 64-bit reports no problem

there has been a proposed fix to ~smp/source/base/image/jpeg.cpp that appears to work, however it requires some additional work to make it a platform (linux) and compiler (gcc) specific fix.

Add metatags to output images identifying the file as having been created using POV-Ray.

File output code for virtually all file formats performs gamma correction on unclipped color values, which leads to issues when color values happen to be negative for some reason and gamma does not happen to be an integer value such as 1.0 or 2.0. As a consequence, subsequent steps (clipping and converting to integer) apparently produce compiler-dependent results. Compiled with Microsift or Intel compilers, POV-Ray seems to write zero brightness in such cases, while compiled with g++ 4.4 (and possibly other compilers) it seems to write full brightness instead.

(See thread news://news.povray.org:119/4ba819f6@news.povray.org for examples.)

The proper solution should be to apply gamma correction after clipping.

When choosing PPM output with a bit depth other than 8 bits per color channel (e.g. +FP16), POV-Ray messes up the colors (see thread news://news.povray.org:119/4babb48f$1@news.povray.org)

POV-Ray 3.7-generated JPEG image output files do not conform to the JFIF standard. Most importantly, the files written do not use the standard YCbCr color model (they seem to use plain RGB instead), nor do they have a proper JFIF tag.

As a consequence, some software may be unable to read the generated JPEG files properly. In addition, it seems that POV-Ray mixes up the Red and Blue channels.

OpenEXR output currently writes an alpha channel when Output_Alpha=off (-UA), and does not write an alpha channel when Output_Alpha=on (+UA), i.e. doing it just the wrong way round.