differential instant radiosity for mixed reality martin knecht, christoph traxler, oliver mattausch,...
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Differential Instant Radiosity for Mixed Reality
Martin Knecht, Christoph Traxler, Oliver Mattausch, Werner Purgathofer, Michael Wimmer
Institute of Computer Graphics and AlgorithmsVienna University of Technology
Motivation
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Motivation
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Problem statement
Virtual objects should seamlessly blend into the real scene
Provide a plausible illusion
Simulation of light interaction between real and virtual objects is necessary
Solution should run at interactive to real-time frame rates
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Related Work
Image Based LightingRitschel and Grosch used a HDR camera to capture environment
Hierarchical Importance Sampling, Clarberg
Real-time Global IlluminationInstant Radiosity introduced by Keller
Imperfect Shadow Maps from Ritschel et. al
Merging Real and Virtual ScenesDifferential Rendering introduced by Fournier and extended by Debevec
Differential Photon Mapping from Grosch5Martin Knecht
Assumptions
Geometry of real scene known
BRDFs of real surfaces are known
Surrounding illumination is distant
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Differential Instant Radiosity for MR
Idea: Combine Differential Rendering (DR) with Instant Radiosity (IR)
Why? DR adds virtual objects to real scene
IR fast method to compute GI solution in real-time
But: Two solutions are needed for DR!
not really
How? Keep track on the light paths
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GI - Instant Radiosity
Use Virtual Point Lights (VPLs) to approximate global illumination
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GI - Instant Radiosity
Use Virtual Point Lights (VPLs) to approximate global illumination
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GI - Instant Radiosity
Use Virtual Point Lights (VPLs) to approximate global illumination
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GI - Instant Radiosity
Use Virtual Point Lights (VPLs) to approximate global illumination
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GI - Instant Radiosity
Use Virtual Point Lights (VPLs) to approximate global illumination
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Differential Rendering
Method to add virtual objects into real scene images
Compute two global illumination solutions and add only difference to real scene image
+ Minimizes visual error from wrong BRDF approximations
- We need to calculate two GI solutions in real-time
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Differential Rendering
Difference BufferGrey means no difference
GI(Real + Virtual) GI(Real)
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Differential Rendering
Masked Video Image Difference Buffer
Final Image15Martin Knecht
How to get GI(Real+Virtual) and GI(Real)?Keep track on the light paths
L: Lightsource
D: Diffuse light bounce
S: Specular light bounce
E: Eye
Heckberts classification
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How to get GI(Real+Virtual) and GI(Real)?Keep track on the light paths
L: Lightsource
D: Diffuse light bounce
S: Specular light bounce
E: Eye
Direct illumination: LDE
Heckberts classification
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How to get GI(Real+Virtual) and GI(Real)?Keep track on the light paths
L: Lightsource
D: Diffuse light bounce
S: Specular light bounce
E: Eye
Direct illumination: LDE
1st bounce diffuse indirect illumination: LDDE
Heckberts classification
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Differential Instant Radiosity for MR
Calculate shading result only once
Decide on path information to which GI solution the result belongs
L[x]D[x]E
L[x]D[x]D[x]E
[x] can be „real“ or „virtual“
All „real“ then add to GI(Real+Virtual) and GI(Real)
One [x] „virtual“, only add to GI(Real+Virtual)19Martin Knecht
LRDRDRE path
Differential Instant Radiosity for MR
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GI(Real + Virtual) GI(Real)
LRDRDRE path
Added to both Buffers
Differential Instant Radiosity for MR
GI(Real + Virtual) GI(Real)
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LRDRDVE path
Differential Instant Radiosity for MR
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GI(Real + Virtual) GI(Real)
LRDRDVE path
Add only to the
GI(Real+Virtual)
Buffer
Differential Instant Radiosity for MR
GI(Real + Virtual) GI(Real)
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Differential Instant Radiosity for MR
Take blocking geometry into account
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LRDRDRE path
Differential Instant Radiosity for MR
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GI(Real + Virtual) GI(Real)
LRDRDRE path
Virtual red wall blocks light!
Differential Instant Radiosity for MR
GI(Real + Virtual) GI(Real)
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Limitations
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Limitations
Double shadowing
Incosistent color bleeding
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Results
Test deviceCore2 Quad CPU Q9550 at 2.8GHz
8GB RAM
NVIDIA Geforce GTX 285 with 1GB VRAM
Windows 7 64-Bit
C# with SlimDX to access DirectX 10
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Results
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Results
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Results
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Results
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Our method uses instant radiosity to simulate mutual influence between objects
Direct Illumination
Indirect Illumination
Combination of Differential Rendering and Instant Radiosity
Lightsources, objects, camera can be dynamic
Cannot take all paths into account
Works reasonable fast (20 – 30 fps)
Conclusion
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Consider all light paths
Add camera artifacts
Camera-based, real-time reconstruction of geometry
Real-time BRDF estimation
Future Work
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Thank you for your attention!
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