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Blurred Radiance
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Blurred Radiance
April 2002
Description:
For my final project of the class I was to precompute the lighting for all
isosurfaces extracted from a scalar field. n number of equally spaced
isosurfaces spanning the full range of the scalar field are computed. The
total amount of incoming light at each point on each surface is computed.
These intensities are then "blurred" across the descete grid values of the
data to produce a 3D array of intensities for each grid point.
One of the reasons this approach is useful is illustrated below. On the left
is an image with standard Open Inventor (OpenGL) lighting on an isosurface.
Then on the right, the same scene is globally illuminated and colored per
vertex. This produces a 3D globally illuminated scene.
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| Standard Open Inventor lighting |
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Globally Illuminated Open Inventor scene colored per vertex |
The technique is applied to a 3D MRI scan of a human brain. 100 different
isosurfaces (which are equally spaced) are generated and the lighting is
computed for each. When testing for ray-triangle intersections IVTrace is used for efficient scene
management. The lighting of each surface takes approximately one hour to
compute using a Dell 1.7GHz Xeon with 1GB ram running Linux. Below are
snapshots taken when different isovalues are viewed using ivview.
Each wall is made out of a 50x50 grid of points
| Globally Illuminated Open Inventor scenes colored per vertex.
Each image contains a different isosurface from the MRI brain scan.
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| Isovalue |
75 |
80 |
85 |
90 |
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| Isovalue |
95 |
100 |
106 |
111 |
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Animation of all 100 isosurfaces isosurfaces.qt
(856K)
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Once the lighting for all isosurfaces is complete, the blurred radiance
intensity array
is computed. Below are screenshots from a surface which used the blurred
radiance intensity array. Notice how much smoother the coloring is.
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