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Currently our rainbow has a circular shape, even though most of it is hidden below the ground plane. You can easily create a rainbow arc by using the arc_angle
keyword with an angle below 360 degrees.
If you use arc_angle 120
for example you'll get a rainbow arc that abruptly vanishes at the arc's ends. This does not look good. To avoid this the falloff_angle
keyword can be used to specify a region where the arc smoothly blends into the background.
As explained in the rainbow's reference section (see "Rainbow") the arc extends from -arc_angle/2 to arc_angle/2 while the blending takes place from -arc_angle/2 to -falloff_angle/2 and falloff_angle/2 to arc_angle/2. This is the reason why the falloff_angle
has to be smaller or equal to the arc_angle
.
In the following examples we use an 120 degrees arc with a 45 degree falloff region on both sides of the arc (rainbow3.pov
).
rainbow { angle 42.5 width 5 arc_angle 120 falloff_angle 30 distance 1.0e7 direction <-0.2, -0.2, 1> jitter 0.01 color_map { [0.000 color r_violet1 transmit 0.98] [0.100 color r_violet2 transmit 0.96] [0.214 color r_indigo transmit 0.94] [0.328 color r_blue transmit 0.92] [0.442 color r_cyan transmit 0.90] [0.556 color r_green transmit 0.92] [0.670 color r_yellow transmit 0.94] [0.784 color r_orange transmit 0.96] [0.900 color r_red1 transmit 0.98] } }
The arc angles are measured against the rainbows up direction which can be specified using the up
keyword. By default the up direction is the y-axis.
A rainbow arc.
We finally have a realistic looking rainbow arc.
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