line - volume intersection ...and texture mapping

line - volume intersection ...and texture mapping

Post by Meessen Christoph » Fri, 11 Apr 1997 04:00:00



Hello,

I'm looking a way to get the x,y,z coordinates of the intersection point
of a line through a volume. The line is defined by two points, one is
the origin.

One volume is a conic

         _______
        \_______/
       /         \
      /...........\
      \___________/

Sorry it is not well drawn. It's a cone cut with paralle surfaces and
othogonal to the central axe. The axe is always vertical in my case.
So we have r1 and r2 for the two radius and h the height of the cone.

Volume 2 is obtained by a revolution around a vertical axis of a
polyline. The polyline is defined as a sequence of points.

I also need the transformation to get the u,v values for these volumes.
Note that mapping on the cone should not strech the texture.

Thanks in advance.

 
 
 

line - volume intersection ...and texture mapping

Post by Stephen Westi » Sat, 12 Apr 1997 04:00:00



> I'm looking a way to get the x,y,z coordinates of the intersection point
> of a line through a volume. The line is defined by two points, one is
> the origin.

> One volume is a conic

>          _______
>    \_______/
>        /         \
>       /...........\
>       \___________/

> Sorry it is not well drawn. It's a cone cut with paralle surfaces and
> othogonal to the central axe. The axe is always vertical in my case.
> So we have r1 and r2 for the two radius and h the height of the cone.

> Volume 2 is obtained by a revolution around a vertical axis of a
> polyline. The polyline is defined as a sequence of points.

I think Jim Kajiya presented a paper at SIGGRAPH about this very
problem; as I recall, he transformed the surface of rotation into a
plane and intersected with a curved ray! I can't dig up the reference
right now; it seems to be before 1985 ('84?).

<snip>
--
-Stephen H. Westin

The information and opinions in this message are mine, not Ford's.

 
 
 

1. HELP:Algorithm for intersection of line and volume

Hi,

A question which I hope some kind soul can solve for me:

I'm doing a project on volume rendering using ray-casting. In the program, the view pane is rotated
about the centre of the volume instead of rotating the whole volume. Given the vector equation of
the line, how do I compute the points at which the ray enter and leave the volume?

Help is greatly appreciated.

Regards,
ohm

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