INF359 assignment 1: Illustrative volume rendering

Several illustrative techniques were implemented using GLSL shaders:

• Cool-to-Warm (Gooch)
• Curvature-controlled contours with depth-varying thickness
• Curvature-controlled contours with uniform thickness

The curvature-controlled contours were implemented using approach published by S. Bruckner and M. E. Gröller in Style Transfer Functions for Illustrative Volume Rendering, Eurographics 2007. In addition, the contour smoothing can be applied. In this mode, the voxel colour is not changed only by considering whether the voxel is on a contour or not (Kindlmann et al. 2003). The contour colour contribution is proportional to the difference of both sides of the inequation. That means that contours are dark black in places with high curvature. On other places, where the curvature is not so high (but high enough to satisfy the a criterion for contour), the colour of voxel is shifted towards black colour only slightly.

Cool-to-Warm shading

Head dataset, cool-to-warm shading applied.

For comparison: Head dataset, Phong shading applied.

Contours

Head dataset, contours with uniform thickness applied.

Head dataset, contours with depth-varying thickness applied.

The difference can be easily seen for example on the button (bottom left) or chin.

Contours with depth-varying thickness and smoothing

Head dataset, thin contours with no smoothing applied.	Head dataset, thin contours with full smoothing applied.
Head dataset, thick contours with full smoothing applied.	Head dataset, contours with medium thickness and some smoothing applied.

Both combined

Head dataset, both cool-to-warm shading and contours with depth-varying thickness and smoothing applied.