Note that there are no INI style equivalents to these options.

Graphical interface versions of POV-Ray such as Mac or Windows have extensive online help. Other versions of POV-Ray have only a few quick-reference help screens. The +? switch, optionally followed by a single digit from 0 to 8, will display these help screens to the Banner text stream. After displaying the help screens, POV-Ray terminates. Because some operating systems do not permit a question mark as a command line switch you may also use the +H switch. Note however that this switch is also used to specify the height of the image in pixels. Therefore the +H switch is only interpreted as a help switch if it is the only switch on the command line and if the value after the switch is less than or equal to 8.

The Quality =n option or +Q n switch allows you to specify the image rendering quality. You may choose to lower the quality for test rendering and raise it for final renders. The quality adjustments are made by eliminating some of the calculations that are normally performed. For example settings below 4 do not render shadows. Settings below 8 do not use reflection or refraction. The values correspond to the following quality levels:

The default is 9 if not specified.

POV-Ray uses a variety of spatial sub-division systems to speed up ray-object intersection tests. The primary system uses a hierarchy of nested bounding boxes. This system compartmentalizes all finite objects in a scene into invisible rectangular boxes that are arranged in a tree-like hierarchy. Before testing the objects within the bounding boxes the tree is descended and only those objects are tested whose bounds are hit by a ray. This can greatly improve rendering speed. However for scenes with only a few objects the overhead of using a bounding system is not worth the effort. The Bounding =off option or -MB switch allows you to force bounding off. The default value is on.

The Bounding_Threshold =n or +MB n switch allows you to set the minimum number of objects necessary before bounding is used. The default is +MB 25 which means that if your scene has fewer than 25 objects POV-Ray will automatically turn bounding off because the overhead isn't worth it. Generally it's a good idea to use a much lower threshold like +MB 5.

Additionally POV-Ray uses systems known as vista buffers and light buffers to further speed things up. These systems only work when bounding is on and when there are a sufficient number of objects to meet the bounding threshold. The vista buffer is created by projecting the bounding box hierarchy onto the screen and determining the rectangular areas that are covered by each of the elements in the hierarchy. Only those objects whose rectangles enclose a given pixel are tested by the primary viewing ray. The vista buffer can only be used with perspective and orthographic cameras because they rely on a fixed viewpoint and a reasonable projection (i. e. straight lines have to stay straight lines after the projection).

The light buffer is created by enclosing each light source in an imaginary box and projecting the bounding box hierarchy onto each of its six sides. Since this relies on a fixed light source, light buffers will not be used for area lights.

Reflected and transmitted rays do not take advantage of the light and vista buffer.

The default settings are Vista_Buffer =on or +UV and Light_Buffer =on or +UL . The option to turn these features off is available to demonstrate their usefulness and as protection against unforeseen bugs which might exist in any of these bounding systems.

The ray-tracing process is in effect a discrete, digital sampling of the image with typically one sample per pixel. Such sampling can introduce a variety of errors. This includes a jagged, stair-step appearance in sloping or curved lines, a broken look for thin lines, moire patterns of interference and lost detail or missing objects, which are so small they reside between adjacent pixels. The effect that is responsible for those errors is called aliasing .

Anti-aliasing is any technique used to help eliminate such errors or to reduce the negative impact they have on the image. In general, anti-aliasing makes the ray-traced image look smoother . The Antialias =on option or +A switch turns on POV-Ray's anti-aliasing system.

When anti-aliasing is turned on, POV-Ray attempts to reduce the errors by shooting more than one viewing ray into each pixel and averaging the results to determine the pixel's apparent color. This technique is called super-sampling and can improve the appearance of the final image but it drastically increases the time required to render a scene since many more calculations have to be done.

POV-Ray gives you the option to use one of two alternate super-sampling methods. The Sampling_Method =n option or +AM n switch selects non-adaptive super-sampling (method 1) or adaptive super-sampling (method 2). Selecting one of those methods does not turn anti-aliasing on. This has to be done by using the +A command line switch or Antialias =on option.

If this difference is greater than the threshold both pixels are super-sampled. The rgb values are in the range from 0.0 to 1.0 thus the most two pixels can differ is 3.0. If the anti-aliasing threshold is 0.0 then every pixel is super-sampled. If the threshold is 3.0 then no anti-aliasing is done. Lower threshold means more anti-aliasing and less speed. Use anti-aliasing for your final version of a picture, not the rough draft. The lower the contrast, the lower the threshold should be. Higher contrast pictures can get away with higher tolerance values. Good values seem to be around 0.2 to 0.4.

When using the non-adaptive method, the default number of super-samples is nine per pixel, located on a 3*3 grid. The Antialias_Depth =n option or +R n switch controls the number of rows and columns of samples taken for a super-sampled pixel. For example +R 4 would give 4*4=16 samples per pixel.

The maximum number of subdivisions is specified by the Antialias_Depth =n option or +R n switch. This is different from the non-adaptive method were the total number of super-samples is specified. A maximum number of n subdivisions results in a maximum number of samples per pixel that is given by the following table.

      Number of samples per    Maximum number of samples
      super-sampled pixel for  per super-sampled pixel for
 +Rn  the non-adaptive method  the adaptive method
  1                1                       9
  2                4                      25
  3                9                      81
  4               16                     289
  5               25                    1089
  6               36                    4225
  7               49                   16641
  8               64                   66049
  9               81                  263169

You should note that the maximum number of samples in the adaptive case is hardly ever reached for a given pixel. If the adaptive method is used with no anti-aliasing each pixel will be the average of the rays traced at its corners. In most cases a recursion level of three is sufficient.

The overall syntax of a scene is a file that contains any number of the following items in any order.

POV-Ray has a number of reserved keywords which are listed below.