Internal animation loop, automatic output file name numbering and the ability to shell out to the operating system to external utilities which can assemble individual frames into an animation, greatly improved the animation capability. The internal animation loop is simple yet flexible. You may still use external programs or batch files to create animations without the internal loop.
External Animation Loop
Clock=n.n option or the
+Kn.n switch may be used to pass a single float value to the
program for basic animation. The value is stored in the float identifier
clock. If an object had a
attached then you could rotate the object by different amounts over different
frames by setting
+K20.0... etc. on
successive renderings. It is up to the user to repeatedly invoke POV-Ray with
Clock value and a different
Output_File_Name for each frame.
Internal Animation Loop
||Sets initial frame number to n|
||Sets final frame number to n|
||Sets initial clock value to n.n|
||Sets final clock value to n.n|
The internal animation loop relieves the user of the
task of generating complicated sets of batch files to invoke POV-Ray multiple
times with different settings. While the multitude of options may look
intimidating, the clever set of default values means that you will probably
only need to specify the
Final_Frame=n or the
+KFFn option to specify the number of frames. All other
values may remain at their defaults.
Final_Frame setting other than -1 will trigger POV-Ray's internal animation loop. For example
+KFF10 causes POV-Ray to render your scene 10 times. If you specified
Output_File_Name=file.tga then each frame would be output as
file03.tga etc. The number of zero-padded digits in the file name depends upon the final frame number. For example
+KFF100 would generate
file100.tga. The frame number may encroach upon the file name. On MS-DOS with an eight character limit,
myscene.pov would render to
Initial_Frame=1 will probably never have to be
changed. You would only change it if you were assembling a long animation
sequence in pieces. One scene might run from frame 1 to 50 and the next from
51 to 100. The
+KFIn option is for this purpose.
Note: If you wish to render a subset of frames such as 30 through 40 out
of a 1 to 100 animation, you should not change
Final_Frame. Instead you should use the subset commands
described in section Subsets of Animation Frames.
Unlike some animation packages, the action in POV-Ray animated scenes does
not depend upon the integer frame numbers. Rather you should design your
scenes based upon the float identifier
clock. By default, the clock value is 0.0 for the initial frame and 1.0 for the final frame. All other frames are interpolated between these values. For example if your object is supposed to rotate one full turn over the course of the animation, you could specify
rotate 360*clock*y. Then as clock runs from 0.0 to 1.0, the object rotates about the y-axis from 0 to 360 degrees.
The major advantage of this system is that you can render a 10 frame animation or a 100 frame or 500 frame or 329 frame animation yet you still get one full 360 degree rotation. Test renders of a few frames work exactly like final renders of many frames.
In effect you define the motion over a continuous float valued parameter (the clock) and you take discrete samples at some fixed intervals (the frames). If you take a movie or video tape of a real scene it works the same way. An object's actual motion depends only on time. It does not depend on the frame rate of your camera.
Many users have already created scenes for POV-Ray 2 that expect clock
values over a range other than the default 0.0 to 1.0. For this reason we
+KFn.n options. For example to run the clock from 25.0 to
75.0 you would specify
Then the clock would be set to 25.0 for the initial frame and 75.0 for the final frame.
In-between frames would have clock values interpolated from 25.0 through 75.0 proportionally.
Users who are accustomed to using frame numbers rather than clock values
Frame_Final=10 for a 10 frame animation.
For new scenes, we recommend you do not change the
Final_Clock from their default 0.0 to
1.0 values. If you want the clock to vary over a different range than the
default 0.0 to 1.0, we recommend you handle this inside your scene file as
#declare Start = 25.0; #declare End = 75.0; #declare My_Clock = Start+(End-Start)*clock;
My_Clock in the scene description. This keeps the
critical values 25.0 and 75.0 in your .pov file.
Note: Details concerning the inner workings of the animation loop are in the section on shell-out operating system commands in section Shell-out to Operating System.
Subsets of Animation Frames
||Set subset starting frame to n|
||Set subset starting frame to n percent|
||Set subset ending frame to n|
||Set subset ending frame to n percent|
||Set the increment to the frame number, default to 1|
When creating a long animation, it may be handy to render only a portion
of the animation to see what it looks like. Suppose you have 100 frames but
only want to render frames 30 through 40. If you set
Final_Frame=40 then the clock would vary from 0.0 to 1.0 from
frames 30 through 40 rather than 0.30 through 0.40 as it should. Therefore
you should leave
to selectively render part of the scene. POV-Ray will then properly compute the
Similarly, if you only want to render a tenth of the frames, you can use
Frame_Step=10 to jump over the nine non-rendered frames between the rendered frames. This option was inspired from megapov, but with two restrictions: only positive step value are supported (forward, no backward rendering) and the value is not available in the SDL
Usually you will specify the subset using the actual integer frame numbers
however an alternate form of the subset commands takes a float value in the
range 0.0 <=n.nnn <=1.0 which is interpreted as a fraction of
the whole animation. For example,
Subset_End_Frame=0.667 would render the middle 1/3rd of a
sequence regardless of the number of frames.
||Turn cyclic animation on/off|
||Turn cyclic animation on|
||Turn cyclic animation off|
Many computer animation sequences are designed to be run in a continuous
loop. Suppose you have an object that rotates exactly 360 degrees over the
course of your animation and you did
rotate 360*clock*y to do
so. Both the first and last frames would be identical. Upon playback there
would be a brief one frame jerkiness. To eliminate this problem you need to
adjust the clock so that the last frame does not match the first. For example
a ten frame cyclic animation should not use clock 0.0 to 1.0. It should run
from 0.0 to 0.9 in 0.1 increments. However if you change to 20 frames it
should run from 0.0 to 0.95 in 0.05 increments. This complicates things
because you would have to change the final clock value every time you changed
Cyclic_Animation=on or using
+KC will cause POV-Ray to automatically adjust the final clock
value for cyclic animation regardless of how many total frames. The default
value for this setting is off.
||Turn field rendering on/off|
||Set odd field flag|
||Turn field rendering on|
||Turn field rendering off|
||Set odd field flag on|
||Set odd field flag off|
Field rendering is sometimes used for animations when the animation is being output for television. TVs only display alternate scan lines on each vertical refresh. When each frame is being displayed the fields are interlaced to give the impression of a higher resolution image. The even scan lines make up the even field, and are drawn first (i.e. scan lines 0, 2, 4, etc.), followed by the odd field, made up of the odd numbered scan lines are drawn afterwards. If objects in an animation are moving quickly, their position can change noticeably from one field to the next. As a result, it may be desirable in these cases to have POV-Ray render alternate fields at the actual field rate (which is twice the frame rate), rather than rendering full frames at the normal frame rate. This would save a great deal of time compared to rendering the entire animation at twice the frame rate, and then only using half of each frame.
By default, field rendering is not used. Setting
Field_Render=on or using
+UF will cause alternate frames
in an animation to be only the even or odd fields of an animation. By
default, the first frame is the even field, followed by the odd field. You
can have POV-Ray render the odd field first by specifying
Odd_Field=on, or by using the