"Thomas de Groot" <tDOTdegroot@interDOTnlANOTHERDOTnet> wrote:
> HDRI_test1 uses a map generated with MegaPOV 1.2.1. From top to bottom, this
> was rendered with MegaPOV map_type 1; MegaPOV map_type 7; and finally with
> version 3.7 beta 32.
>
> HDRI_test2 uses a map from a hdri collection, and was rendered identically
> with megapov and 3.7.
>
> The scenes rendered with map_type 7 are clearly different. So, in what
> situations is this particular parameter used? The documentation is unclear
> about this.
>
> Thanks for any info.
>
> Thomas

To further clarify the differences for you:

lat/long (spherical panorama): Each x coordinate represents the angle around the
sphere from 0 to 360deg, each y coordinate represents the vertical angle from
-90deg to +90deg.  This results in the poles being quite stretched in the
unmapped image, but this is not an issue.

mirror ball: A direct image (or could be generated using software) of a mirrored
ball.  Each point of the visible side of the ball reflects the scene based on
the angle of incidence.  The centre reflects straight back, progressing to a
reflection from behind the ball at the edges (or as close as the camera
parallax/perspective will allow).  The progression from the front to rear
reflection is non-linear as it is related to the angle of incidence with the
surface of the sphere.  This results in a pinching effect from the edges of the
ball due to poor resolution at this area.  These are not usually used for direct
mapping, but are usually converted to lat/long or angular map types.

Angular (also called probe sometimes):  Appears similar to mirror-ball as it is
circular and represents the scene from front to back as it progresses from the
center to the edges.  However, the progression here is linear (i.e.,
centre=0deg, 1/2way out=90deg, edges=180deg).  The linear progression helps to
preserve an adequate resolution for the entire map area and is also very simple
to unwrap and map.

-tgq

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