Computing FOV footprint

Computing FOV footprint

Post by Happy Jo » Fri, 11 Jul 2003 13:53:20



Given coordinate system, eye positioned
at {x0 y0 z0}, the FOV, and the direction
I am looking (in angles about x,y,z axis)...
How can I calculate the footprint of the FOV
in a plane parallel to z (altitude) ?
(I really need the x,y of the 4 points of my
rectangular fov footprint at plane z = z0)
 
 
 

Computing FOV footprint

Post by Paul Nicholl » Fri, 11 Jul 2003 16:10:49


I think that the (x,y) of each of the 4 points at z0 will be (x0,y0) because
the eye position is right at the very tip of the view fustrum...


Quote:> Given coordinate system, eye positioned
> at {x0 y0 z0}, the FOV, and the direction
> I am looking (in angles about x,y,z axis)...
> How can I calculate the footprint of the FOV
> in a plane parallel to z (altitude) ?
> (I really need the x,y of the 4 points of my
> rectangular fov footprint at plane z = z0)


 
 
 

Computing FOV footprint

Post by Hans-Bernhard Broeke » Sat, 12 Jul 2003 01:04:57



> Given coordinate system, eye positioned at {x0 y0 z0}, the FOV, and
> the direction I am looking (in angles about x,y,z axis)...  How can
> I calculate the footprint of the FOV in a plane parallel to z
> (altitude) ?  (I really need the x,y of the 4 points of my
> rectangular fov footprint at plane z = z0)

There are no such points at all in the plane your eye is in (z=z0).
In other planes of constant z, there can be anywhere between zero and
four, depending on your FOV, view direction and roll angle.  E.g, if
you're looking straight up, with a full FOV smaller than 180 degrees,
you will not have any "footprint" at all in a plane below your eye
point.

To find them, shoot rays from your eye point into each view frustum
edge direction, and see whether (and where) there intersect that
plane.
--

Even if all the snow were burnt, ashes would remain.

 
 
 

1. Horizontal FOV to vertical FOV conversion

Hi,

I'm currently making a program which displays a 3D scenes through a virtual
camera. One of the camera parameter is the FOV measured in a vertical
orientation. I call this parameter "FovY" (Y for Y axis).

I'm getting the Fov value from a camera created in 3DSMax. Unfortunately,
the given Fov is measured in an horizontal orientation. I call this Fov
"FovX".

I would like to get this FovY information, and it seems the only way to get
it is to convert the FovX given a conversion formula.

3DSMax can displays the FovY, but there is no way to get this information.
I've been drawing curves which shows the relation between the FovX and the
FovY given an AspectRatio. When the aspect ratio is 1, you get a straight
line going from (0,0) to (180,180). It corresponds to f(x) = x.
(FovX is represented by the horizontal axis, FovY by the vertical)

But when the AspectRatio increases, you don't get a linear relation. You get
a curvy line, which centers going down in the direction of the point
(0,180).

Is there a known formula to convert FovX to FovY, or is this just a trick
from 3DSMax ?

regards,

Hadrien - Darken/Loveboat

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