[MINC-users] ray_trace issue!

[Lasse Riis Østergaard]

Hi again

I now see that the issue is related to make_slice and not ray_trace!

In the example I provided make_slice creates this:

Q 0.3 0.3 0.4 10 1 2 2 F F
 0 1 1 1 1

 98.8034 140.093 0.842139
 98.8034 -59.1943 6.75685
 -100.572 140.093 0.842139
 -100.572 -59.1943 6.75685

 0 0 1
 0 0 1
 0 0 1
 0 0 1

I had expected a constant z-value of 5. Does make_slice find the closest 
slice in voxel space?

Lasse

Lasse Riis Østergaard wrote:
> Hi
>
> Any ray_trace experts here?
>
> I am using ray_trace to render images of surface cross sections on  top 
> of volume cross sections. I have been following the steps in David's 
> tutorial (Example 14). This works very fine if the z-axis in world and 
> voxel space are parallel. If this is not the case their seem to be an 
> issue with the texture mapping as the gray levels are not interpolated 
> correct!
>
> Here is what I do:
>
> 1. make_slice volume.mnc slice.obj z w 5 2 2
> 2. plane_polygon_intersect surface.obj lines.obj z 5
> 3.  ray_trace -output image.rgb -nolight -line_width 1 lines.obj -gray 0 
> 300 volume.mnc 0 1 slice.obj -size 1024 1024 -bg white -crop -top -sup 3
>
> ray_trace maps the grey levels of a slice along the z-axis in voxel 
> space - not in world space!
>
> By inspection I have found that the rendered slice exactly corresponds 
> to z=78 (voxel space) wich cuts through z-coordinates 0.9-6.8 in world 
> space.
>
> Am I doing anything wrong?
>
> cheers
> Lasse
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