[I think this already came up, but I can't find the thread any more, One
of these days I'll have to set up a full text index for povray.*]

While playing around with superellipsoids and the orthographic camera I
found that the superellipsoid vanishes if the camera is pointing exactly
along the X axis. Here is a short scene file to demonstrate the effect:

---8<------8<------8<------8<------8<------8<------8<------8<---
#include "colors.inc"

global_settings {
        assumed_gamma 1.0
}


light_source {
    <2000, 2000, -2000>
    color White
}

camera {
        location <90, 0.000000, 0.00000>
        look_at <0, 0, 0>
	angle 10
	orthographic
}

superellipsoid {
    <0.25, 0.25>
    scale <2.5, 1, 3>
    pigment {
	checker color Yellow, color Red
	scale 10
    }
}

background { color rgb<0.2, 0.4, 0.8>  }
---8<------8<------8<------8<------8<------8<------8<------8<---

If you replace one of the 0.000000 values in the camera location by
0.000001 the superellipsoid miraculously appears again.

The povray statistics say:

Ray->Shape Intersection          Tests       Succeeded  Percentage
----------------------------------------------------------------------------
Superellipsoid                   77361               0      0.00
----------------------------------------------------------------------------

So it looks like the ray->shape Intersection test for superellipsoids
doesn't work if the ray is exactly parallel to the x axis.

With a non-orthographic camera this probably doesn't matter since it
affects at most one ray.

	hp

PS: I hope it is okay to include short scene files directly in the text
instead of posting them to povray.text.scene-files.

-- 
   _  | Peter J. Holzer    | Nicht an Tueren mangelt es,
|_|_) | Sysadmin WSR       | sondern an der Einrichtung (aka Content).
| |   | hjp### [at] wsracat      |    -- Ale### [at] univieacat
__/   | http://www.hjp.at/ |       zum Thema Portale in at.linux

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