High-Quality Pre-Integrated Volume Rendering Using Hardware Accelerated Pixel Shading

1
High-Quality Pre-Integrated Volume Rendering
Using Hardware Accelerated Pixel Shading
Klaus Engel, Martin Kraus, Thomas
Ertl Visualization and Interactive Systems
Group University of Stuttgart, Germany
Siggraph/Eurographics Workshop on Graphics
Hardware 2001
2
Volume Rendering Quality Improvement

• Higher sampling rates additional tri-linearly
  interpolated slices
• 2D textures
• render intermediate slices using multi-texture
  approach(Rezk-Salama,Engel et al., GH2000)
• - 3D textures
• render additional slice polygons
• But
• decreases rendering speed due to additional
  rasterization
• many additional slices required even for
  low-resolution volumes
• non-linear transfer functions not sufficient to
  sample volume with the Nyquist frequency of
  scalar data

3
Volume Classification
transfer functions
Pre- classification
voxels
Post- classification
4
Pre-Integrated Volume Rendering

• The approach
• texture-based (2D/3D)
• ray-segments computed in a pre-processing step
• pre-computed ray-segment lookup (dependent
  texture)
• small number of slices gt fast
• Especially suited for
• low resolution volume data
• non-linear transfer functions
• Capable of
• high-quality rendering
• direct volume rendering, volume shading,
  isosurfaces

5
Pre-integrated Volume Rendering - Idea
slice-by-slice
slab-by-slab
hardware-accelerated implementation on NVidia
GeForce3 chip
6
Pre-integrated Volume Rendering - Texel Fetch
front slice
back slice
7
Results Direct Volume Rendering
8
Isosurfaces
Isosurfacesparticular dependent texture
sb
96
32
sf
32
96
9
Isosurfaces Gradient Interpolation

• g IP gb (1-IP) gf interpolation weight IP
  (siso sf)/(sb sf)
• store gradient with scalar data in RGBA texture
• store IP in dependent texture
• implement interpolation in reg. combiners

sb
g
front slice
back slice
10
Pre-integrated Volume Rendering Register
Combiners

• Combiner 01 rebuild gradients (front back)

gx gy gz
gy gz gx
s
s

• Combiner 2 interpolate gradients

IP (siso sf)/(sb sf) g IP gb (1-IP) gf

• Combiner 3-7 shading (isosurface or volume)

pmax 256
11
(No Transcript)
12
Results Direct Volume Rendering, Random TF
13
Results - Isosurfaces