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My presentation of Mmvr2013.
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Gradient Free Visualization with Multiple Light Approximates
MMVR2013
ked
The difficulties of MRI visualization
The rendering results of Phong shading
CT vis. MRI vis.
Attributed to unreliable gradient
Caused by Noise Numerical errors
Unreliable gradient
Caused by Noise Numerical errors
Org. Estimated gradient
Unreliable gradient
Occurs in the region of low magnitude Affected by noise
Org. Estimated gradient
Traditional visualization
Depends on gradient information Noisy rendering result
Org. Estimated gradient Phong shading
Gradient-free visualization
Gets rid of the tricky estimation Improves the quality
Org. Estimated gradient Phong shading
Gradient-free
Two pass approach
Our method: the first pass
Off-line processing Accumulates attenuation maps for orthogonal
directions
Our method: the second pass
Real-time interaction Lights are linearly interpolated to approximate the
contribution of attenuation maps
Derived from
Integral of volume rendering
Derived from
Integral of volume rendering
Color Attenuation
Attenuation map:pre-computed summation Integral for volume rendering
+xSmoothing function
Attenuation map:opposite direction Integral for volume rendering
-x +xvmax
6 orthogonal att. maps
-x +x
+y
-y-z
+z
Approximation of a light
Tx
Ty
D
Multiple light sources
Summation of contribution
from each light
Shading = lighting x color
Global attenuation factor
Att. factor
Small: uniform lighting Large: surface enhancement
Lighting results
Lighting can improve spatial perception Our approach provides more details
No lighting Z lighting 3-point + head lights
Explorative model: plane cutting
Before After
Voxel of the cutting plane
Explorative models: modified MIP
Rewrites the integral of volume rendering
Spatial information is majorly provided by the lighting
Explorative models: modified MIP
Similar to the effect of MIP Contains more spatial information
Org.
Modified MIP
Experiments
Dataset Data resolution
Att. map resolution
Pre-computing(s)No avg. / avg.
Real-timeFPS
MRI brain 256x256x109 200x200x170 6 / 16 12.5
CT head 256x256x113 200x200x177 7 / 17 9.1
CT chest 384x384x240 200x200x125 5 / 13 10.0
Acer Aspire 8950G 2GHz Quad Core CPU 4G memory AMD RadeonHD 850M GPU
Demo
http://www.youtube.com/watch?v=2rois9seJDw http://www.youtube.com/watch?v=ZsZAcTGDyuA
The other results
Thx.