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gbiv
12-14-2006, 12:38 PM
I've been looking into this topic for the past week or so. I'm trying to address the problem of being able to see the "slices" in the volume. I ran across a post that stated pre-integrated vr will fix these issues so I went about downloading the sample demo and trying it out. I'm still seeing the same effects that are present in my current implementation of vol rendering, here is a clip to see the effects in the pre-Integrated demo pg:
pre-Integrated vr demo (http://www.vrac.iastate.edu/~biv/preInt.avi)
No matter how I adjust the tf, the effect is still there. My question is, is there any way to get rid of this?
:confused:
biv

Klaus
12-15-2006, 12:39 AM
Pre-integrated volume rendering can fix artifacts due to high frequencies in the transfer function. It does not remove the need to sample the data according to the Nyquist-Shannon Sampling Theorem, i.e. you have to sample at least twice per voxel to reconstruct the volume data properly.

If i remember correctly, you can increase the sampling rate in demo with the key '5'. If you do that multiple times you will see that the artifacts will slowly disappear.

In particular, the stripes you see at the volume boundary are due to discontinuities of the sampling position at the boundary, i.e. you see the edges of the slice polygons. You can fix those artifacts by adding noise to the sampling position (not in the demo) or by starting the all rays exactly at the volume boundary, for example in a volume raycaster.

- Klaus

gbiv
12-15-2006, 11:28 AM
This is exactly the info I was looking for!
:D
Thanks!