RE: [Algorithms] Obscuring objects

[Gareth L. <GL...@cl...>]

Couldn't you calculate the frustum from the point to the 4 corners of the
screen, then intersect the 4 planes with the sphere ? Couldn't the question
be posed as "Can I see the view port from a point, or it is being occluded"

I know it's not the normal way of doing it, but most of mine aren't. I not
sure it's the best way for a sphere, but it would work nicely ( I think )
for more complex shapes, or testing multiple occluders.

/me must have missed something, cause it looks like a really useful idea to
me :)

> -----Original Message-----
> From: Lars Wilke [mailto:la...@ch...]
> Sent: 28 July 2003 19:25
> To: gda...@li...
> Subject: [Algorithms] Obscuring objects
> 
> 
> This may be a dumb question, but here goes.
> 
> How do I determine if an object in the scene is obscuring 
> another point
> in 3D in screen coordinates?  It could be something as simple 
> in my case
> of determining whether the bounding sphere obscures the point.  So,
> posing the question in another way, ho do I find the equation of the
> projected circle in screen coordinates of a sphere in 3D?
> 
> Thanks in Advance.
> 
> Lars Wilke
> 
> 
> 
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