Table of Contents
The Frame_Step=n (+STPn) option introduces breaks in the order of rendered steps. It splits the order of rendered frames into a 'virtual' and a 'real' order.
'Virtual' order is the same as the traditional (used in POV-Ray™ 3.5) order described with Initial_Frame, Final_Frame, Initial_Clock, Final_Clock, Subset_Start_Frame, Subset_End_Frame. This order is what the scripts reads from initial_frame, clock_delta and other animation related build-in tokens in SDL.
'Real' order is a subset of 'virtual' order. It is every n-th frame where n is the value of Frame_Step. Selected frames are reordered (with ascending or descending order) according to the sign of Frame_Step option.
Frame_Step is supposed to use parallel rendering over one source with one location shared between instances of renderer.
Example 2.1. Influence of Frame_Step on generated files
The following command line:
megapov +Iscene.pov Initial_Frame=1 Final_Frame=5 +FN
causes the creation of files in such order:
scene1.png scene2.png scene3.png scene4.png scene5.png
while when using Frame_Step:
megapov +Iscene.pov Initial_Frame=1 Final_Frame=5 +FN Frame_Step=-2
causes a subset of it in the following order:
scene5.png scene3.png scene1.png
![]() | Important |
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Frame_Step different than 1 works fine for those animations where variables are not passed between frames when using external files and where the next frame does not use values derived from a previous (in the meaning of virtual order) frame by other ways. |
POV-Ray™ 3.5 does not allow the End_Row command line option (+ER) to be 1, but rather forces the value, indirectly, to be the last row in the image. Basically it seems to be impossible to render the top row of an image by itself. MegaPOV contains a fix for this behavior. The change also makes the +SR/+ER flags consistent with the behavior of the +SC/+EC flags.