Alain Martel <kua### [at] videotronca> wrote:

> Tried projected_through with a filtering pattern creating a gradient. It
> don't work. You get a warning about projected_through requiring a
> texture-less object, and the pigment or pattern is ignored.

Yeah - RTFM shows that it doesn't do what I had thought it did.

https://wiki.povray.org/content/Reference:Light_Source#Projected_Through

Projected Through
You can use projected_through with any type of light source. Any object can be
used, provided it has been declared beforehand. Projecting a light through an
object can be thought of as the opposite of shadowing, in that only the light
rays that hit the projected through object will contribute to the scene. This
also works with area lights producing spots of light with soft edges. Any
objects between the light and the projected through object will not cast
shadows, additionally any surface within the projected through object will not
cast shadows. Any textures or interiors on the object will be stripped and the
object will not show up in the scene.

The syntax is as follows:

light_source {
  LOCATION_VECTOR, COLOR
  [LIGHT_SOURCE_ITEMS...]
  projected_through { OBJECT }
  }


Maybe use a disk with a cylindrical pattern and a gradient, or a sphere with an
onion and a gradient.

We don't actually have any inbuilt pattern that would give a conical gradient,
do we?

Maybe use a cylindrical gradient with a spherical warp.
Put the camera in the center of it.

Then just write a function that limits the locus of the gradient and gives the
right color-mapping for the glory effect.

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