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

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Geometry Shader

5Geometry shaders

RASTERIZATION

FRAMEBUFFER

FRAGMENT SHADER

VERTEX SHADER

GEOMETRY SHADER

WSCG'2008 - February 2008

Example

6Geometry shaders

Input primitive

Output primitives

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Our method overview

7Our Algorithm

View 1

View 2

Geometry

Shader

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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)

WSCG'2008 - February 2008 17

Thank you!

francois.desorbier@univ-paris-est.fr