Lecture 7.1: Flow Vis: Texture Approaches

• Flow Volumes (Max, Becker, & Crawfis, Vis '93)
• Texture Splats (Crawfis & Max, Vis '93)
  • General splatting (Westover, SIGGRAPH '90)
    • for each voxel
            compute contribution to image
            composite with previous voxel contributions
    • each splat modeled as Gaussian
            precompute splats; variable resolution
            originally no perspective
    • enhancements: hierarchical splatting (Laur & Hanrahan, SIGGRAPH '91)
      • use octtree to estimate contribution of each splat
      • match precision to anticipated size
      • approximate splats by RGBA Gouraud-shaded pgons
  • Texture Splat Method
    • for each data point
            splat textured kernel into image
  • Options
    • splat shape altered to show:
            orientation
            magnitude
    • splat feature phase altered to construct animated textures
• Spot Noise (van Wijk, SIGGRAPH '91; de Leeuw & van Wijk, Vis '95)
  • Method
    • construct spot noise texture by composition of randomly weighted and positioned spots
    • use vector field to control local spot attributes
            magnitude -> spot scaling (area preserved)
            direction -> spot orientation
  • Extension
    • bend spots along neighboring streamlines
            for sharply curving flows
            for diverging/converging flows