POV-Ray : Newsgroups : povray.newusers : image_map to tilted and rotated triangle centered and scaled : Re: image_map to tilted and rotated triangle centered and scaled Server Time 6 Jul 2022 18:20:53 EDT (-0400)
 Re: image_map to tilted and rotated triangle centered and scaled
 From: Bald Eagle Date: 31 Mar 2022 14:25:00 Message:
```
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You might be able to use

f_th(x,y,z): f_th() is a function that is only useful when combined with other
surfaces. It produces a value which is equal to the theta angle, in radians, at
any point. The theta angle is like the longitude coordinate on the Earth. It
stays the same as you move north or south, but varies from east to west. Also
look at f_ph and f_r

and

f_ph(x,y,z): When used alone, the PH function gives a surface that consists of
all points that are at a particular latitude, i.e. a cone. If you use a
threshold of zero (the default) this gives a cone of width zero, which is
invisible. Also look at f_th and f_r

in Functions.inc

https://wiki.povray.org/content/Reference:Functions.inc
```