Subject:
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Re: 3D matrix math question
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Newsgroups:
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lugnet.cad.dev
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Date:
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Sun, 14 Dec 2008 21:33:34 GMT
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Viewed:
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12940 times
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In lugnet.cad.dev, Anders Isaksson wrote:
> Travis Cobbs wrote:
>
> > Unfortunately, as far as I can tell, the projection matrix doesn't
> > produce useful results for points that lie outside the view frustum.
>
> Is there some 'easy' way to determine if the control points are in or out of
> frustum?
>
> Is there any other way to transform points, without considering the frustum
> (Well, obviously there is at least one, but it's the long way of calculating
> the matrices and transformations yourself instead of using OGL)?
Well, I know where the camera is, and I can create vectors from the camera to
both end-points of the conditional line, and to both control points. I'm pretty
sure that the calculation could be done with just this information. However,
I'm not sure off-hand what to do with those vectors, and I suspect it would be
slower than what I'm doing now. Since Tim suggested something that I think will
work, and is much simpler, I'm going to try that first.
> Can you create a 'secondary view' with the same viewing angle but wide angle
> frustum, just to get the transformation of the control points and the cond.
> line? This would obviously take more time (if possible at all), so you would
> need a fast and easy way to determine if it is necessary...
This is probably possible, and it only has to be done once per frame, so it
shouldn't have a big performance impact. However, 180 degrees is the widest
possible viewing angle, and so the control points could still in theory end up
outside the frustum in some circumstances.
--Travis
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Message is in Reply To:
 | | Re: 3D matrix math question
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| (...) Is there some 'easy' way to determine if the control points are in or out of frustum? Is there any other way to transform points, without considering the frustum (Well, obviously there is at least one, but it's the long way of calculating the (...) (16 years ago, 14-Dec-08, to lugnet.cad.dev)
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