gdalgorithms-list

RE: [Algorithms] Maximum Distance Point To AABB

[Tom F. <to...@mu...>]

I wouldn't worry about trying to bin the smaller mipmap levels - they are so
much less memory than the larger ones that it's pointless trying to bin them
- (a) you save very little memory, (b) even close-to things can use smaller
mipmaps (if they are edge-on) and (c) most hardware doesn't support having
missing small mipmaps - you'll only confuse it horribly.

Saving the larger mipmaps is obviously a win though.

Tom Forsyth - Muckyfoot bloke.
Whizzing and pasting and pooting through the day.

> -----Original Message-----
> From: Joe Ante [mailto:jo...@ti...]
> Sent: 31 July 2000 22:43
> To: 3D Algorithms
> Subject: [Algorithms] Maximum Distance Point To AABB
> 
> 
> Hi,
> 
> For my terrain engine texture synthesizer, I want to 
> dynamically load the
> mipmap levels only when they are needed and delete them when 
> they are not
> needed anymore.
> The terrain is subdivided into little chunks which all have their own
> texture. So I would like to find out the minimum and maximum 
> Distance from a
> point to the AABB enclosing the terrain chunk.
> 
> The minimum distance was easy, but how do I get the maximum 
> distance to the
> AABB?
> 
> Thanks in advance.
> bye joe
> 
> _______________________________________________
> GDAlgorithms-list mailing list
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> http://lists.sourceforge.net/mailman/listinfo/gdalgorithms-list
> 

Re: [Algorithms] Maximum Distance Point To AABB

[Joe A. <jo...@ti...>]

> I wouldn't worry about trying to bin the smaller mipmap levels - they are so
> much less memory than the larger ones that it's pointless trying to bin them
> - (a) you save very little memory, (b) even close-to things can use smaller
> mipmaps (if they are edge-on) and (c) most hardware doesn't support having
> missing small mipmaps - you'll only confuse it horribly.
Good point, but I have a another problem I need the maximum point for, I
want to have different detailTextures, which are not to be drawn when they
are very far away.

But having spent some background thinking on the problem now, is it true
that the point(on the AABB) with maximum distance to the other point, is
always on one of the 8 vertices? Which means I only have to find out which
of the 8 vertices is most far away from the other point.

bye joe

Re: [Algorithms] Maximum Distance Point To AABB

[Tom H. <to...@3d...>]

At 03:09 PM 8/1/2000 +0200, you wrote:
>Good point, but I have a another problem I need the maximum point for, I
>want to have different detailTextures, which are not to be drawn when they
>are very far away.
>
>But having spent some background thinking on the problem now, is it true
>that the point(on the AABB) with maximum distance to the other point, is
>always on one of the 8 vertices? Which means I only have to find out which
>of the 8 vertices is most far away from the other point.

For the nearest point you can find places on the AABB that are closer than 
the vertices, but for the farthest point I can't come up with any 
conditions where that would be the case. Its possible that 2 or 4 points of 
a face of the AABB will be equidistant to the test point, but in that case 
it doesn't matter since the distance to any one of them will give you the 
right answer.

Tom