Computer Graphics & 3D Painting
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Transcript of Computer Graphics & 3D Painting
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Computer Graphics& 3D Painting
Xia Jiazhi
Central South University
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Xia Jiazhi
• Lecturer at Central South University
• Received Ph.D. at Nanyang Technological University, Singapore, in 2011
• Research: Computer Graphics and Human-Computer Interaction
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What is Computer Graphics?
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What is Computer Graphics
• A technique to generate digital images from 3D models using computer.
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Which one is the real BMW?
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Is it Fake or Photo?
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The image may cheat us
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Why Computer Graphics?
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Why computer graphics
• About 50% of the brain neurons are associated with vision.• Dominant form of computer output.• Enable scientists (also engineers, doctors, and general users) to
observe their simulation and computation.• Computer graphics is application driven!
– Movie
– Game
– Computer-aided design (CAD)
– Medical imaging
– Computer art
– Graphical user interface (GUI)
– Scientific visualization
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Movies
• If you can imagine it, it can be done with computer graphics.
• More than one billion dollars on special effects. More and more of these images exist only within the memory of a computer. No end in sight for this trend!
• Computer graphics is now as much a part of the video and movie production industry as stuntmen and makeup.
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Video Games
• Games are the driving force in computer graphics.
• Games market is the stimulus for the powerful graphics processors (GPU)
Spacewar 1961 Counter Strike 2005
Crysis 3 2013
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Computer-Aided Design(CAD)• Today, most mechanical and electronic designs are executed entirely on computer.
Increasingly, architectural and product designs are also migrating to the computer. Automated tools are also available that verify tolerances and design constraintsdirectly from CAD designs.
• CAD can significantly reduce the design cycles for industrial products, e.g., the mobile phones
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Graphical User Interface(GUI)
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Visualization
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How Computer Graphics Works?
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Simulating the Everyday World
• Three broad areas:– Modeling(Geometric) = Shape– Animation = Motion/Behavior– Rendering = Appearance
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Representing the Shape
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Geometric Modeling
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Geometric Modeling
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Geometric Modeling
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Animating the world
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Animation
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Natural phenomena simulation
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Rendering
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Rendering• Rendering is the process of generate an image from a scene, which contains
geometry, viewpoint, texture and lighting information. It is similar to photography or cinematography.
• Simulation of realistic lighting, shadows, atmosphere, color, texture and optical effects such as refraction of light or motion-blur seen on moving objects.
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Representing the Surface Details
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Texture Maps
• How is texture mapped to the surface?– Dimensionality: 1D, 2D, 3D
– Texture coordinates (s, t)• Surface parameters (u, v)
• How to assign the Surface parameters?– Parameterization!
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3D Painting
• Assign colors to vertices directly in a painting interface– WYSIWYG(What You See Is What You Get) system
• Painting on self-occluded model
– A lot of manual work, even impossible
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Start from Reality
From Jeremy Birn
Model
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Start from Reality
Model + illumination
model
From Jeremy Birn
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Start from Reality
Model + illumination + Texture
Model + illumination
Model
From Jeremy Birn
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3D Painting
• An interactive technique for 3D model surface properties editing
• 3D model surface properties are required by reconstructing the surface details of the real object– Color– Illumination– Transparency– Normal ( bump mapping)– Displacement mapping– ……
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The 3D Painting System
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The Challenge of 3D Painting
• The dimension– 3D interaction + 3D display– 2D interaction interface is still the major method
of industry [P. Hanrahan et al. 1990]
• Operation– The occlusion is a challenge to interaction even
in real world
• The Creation skill– General users lack the professional creation skill
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1. Occlusion
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Our Method
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Depth Layer
Layer 1 Layer 2
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Depth peeling
Layer 1 Layer 2
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Region Segmentation
The pixel adjacent
information
Region adjacent
information
Region Segmentation
Depth Information
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Layer-aware Interaction
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Layer-aware Interaction
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A complete painting demo
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2. The difficulty of creation
• 3D painting requires professional creation skill
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Decal System
• Copy+Paste
Schmidt et al. 2006
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Exponential Map
Can only control the center point and the direction
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Sketch-based texture mapping
• Free control of the texture deformation
• More close to painting experience of general users
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Sketch-based texture mapping
Extended exponential map
Texture map
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Extended exponential map
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Comparison
Extended exponential map[Sun et al. 2013]
Exponential map[Schmidt et al. 2006]
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A painting demo
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Thanks! & Question?