accelerated stereoscopic rendering using gpu françois de sorbier - université paris-est france...
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Accelerated Stereoscopic
Renderingusing GPU
François de Sorbier - Université Paris-Est France
February 2008
WSCG'2008
WSCG'2008 - February 2008
Problematic
2Introduction
Two-pass renderingComputational time doubled
WSCG'2008 - February 2008
• Shared attributes on vertices– Colour– Geometry– etc
• Use graphical processor Duplicate the geometry Transformations according to the viewpoint
Geometry Shaders
Hypothesis
3Introduction
WSCG'2008 - February 2008
• Geometry shaders• Our algorithm• Results• Conclusions
Outline
4
WSCG'2008 - February 2008
Geometry Shader
5Geometry shaders
RASTERIZATION
FRAMEBUFFER
FRAGMENT SHADER
VERTEX SHADER
GEOMETRY SHADER
WSCG'2008 - February 2008
Example
6Geometry shaders
Input primitive
Output primitives
WSCG'2008 - February 2008
Our method overview
7Our Algorithm
View 1
View 2
Geometry
Shader
WSCG'2008 - February 2008
Images generation
8Our Algorithm
• Fragment shaders processing• Fragment's origin• Rendering buffer selection (Multiple Render Targets)• Standard operations
• Rendering into two textures• Using FrameBuffer Object
• MRT + FBO involve constraints
WSCG'2008 - February 2008
Constraints
9Our Algorithm
• No separated depth buffer Use painter algorithm on objects Back Face Culling
• Have to render a fragment into the two buffers
Colour and alpha set to 0 Mix function for blending
SA1
DRGBA+
SA.
SRGBA=
FRGBA
WSCG'2008 - February 2008 10Our Algorithm
WSCG'2008 - February 2008
Improvement hypothesis
11Our Algorithm
?
WSCG'2008 - February 2008
Algorithm
12Our Algorithm
• Get depth map• Transmit vertices' position with duplicated
geometry (GS)• Apply our own depth test (FS)
• Get correct position in the depth map• Comparison with current fragment depth
WSCG'2008 - February 2008 13Our Algorithm
WSCG'2008 - February 2008
No illumination 163 304
163 158
82 158
82 107
83 156
83 105
Rendering method Basic (FPS) Our algorithm (FPS)
No illumination + Depth map
Per-vertex illumination
Per-vertex illumination + Depth map
Per-pixel illumination
Per-pixel illumination + Depth map
Results
14Results
nVidia GeForce 8800 GTX80.000 triangles
WSCG'2008 - February 2008
Conclusions
15Conclusion
• Limitations “home made” depth test
• Advantages Only one rendering pass Reduces computational time First release of geometry shader
WSCG'2008 - February 2008
Extensions
16Conclusion
• Depth test enhancement– Separated depth buffers?– Algorithm?
• Autostereoscopic screens– Up to 8 views (first results)
