Cube Map Query Question...

OpenGL
1

I have a series of vectors, each of which is assigned to one of 6 cube map walls and an x/y value on those walls, depending on each vector’s direction.

The full set of possible vector directions corresponds to a sphere, while the walls of the cube map are each 2D.

If I want to search for vectors pointing in directions along a circular region along the surface of this sphere, this circle on the surface of the sphere would have to be projected or otherwise transformed onto the surface of the cube map, in order to account for the distortion. I assume it would be a derived form of a point in circle test ultimately.

Likewise, if I query a rectangular region on the surface of the sphere, this too much be projected or otherwise transformed to account for distortion.

What kind of techniques or relationships might be helpful in transforming this test? I can’t seem to find any lead on it.

2

A circle projected onto a plane would be a conical projection and would fall into 3 possible categories. It would be either a circle an ellipse or a parabola depending on the conical intersection with the plane. Each cube face forms a plane, any circle would be a cone. Now you may have a much simpler case in mind, I do not know because you leave a lot unspecified. A circle centered around the center of the cubemap would be a simpler case but somewhat different from what I described. It would be a planar intersection with the cube.