Graphics Creating Virtual World II CSE 425 Virtual

Overview n CGVR Rendering 3 D Rendering Pipeline n Global Illumination n n Texture

Rendering n 3 D Rendering Pipeline n n n n CGVR Modeling transformations Viewing

Introduction to Rendering n CGVR Visual Realism Hidden surface removal n Lights and materials

3 D Rendering Pipeline CGVR 3 D Geometric Primitives Modeling Transformation Lighting Viewing Transformation

3 D Rendering Pipeline CGVR 3 D Geometric Primitives Modeling Transformation Lighting Transform into

Hidden Surface Removal n CGVR Motivation I n Surfaces may be back-facing Back-Facing Polygon

Hidden Surface Removal (cont. ) n CGVR Motivation II n Surfaces may be overlapped

Hidden Surface Removal (cont. ) n CGVR Algorithms n n n Back-face detection Depth

Modeling Light Sources CGVR n n n Describes the intensity of energy Leaving a

Light Source Models n CGVR Simple mathematical models: Point light n Directional light n

Modeling Surface Reflectance CGVR n Describe the amount of incident energy n Arriving from

Reflectance Model n CGVR Simple analytic model: Diffuse reflectance + n Specular reflectance +

Emission & Ambient n Emission n n CGVR Represents light emanating directly from polygon

Shading CGVR Determine a color for each filled pixel n Polygon Shading n Flat

Ray Tracing n CGVR Technique for global reflection and transmission Visible-surface detection n Shadow

Radiosity n Energy/unit area leaving a surface n The method for describing diffuse reflections

3 D Rendering Pipeline 3 D Primitives CGVR 3 D Modeling Coordinates Model Transformation

Texture Mapping n CGVR Texture mapping Superimpose a completely independent twodimensional image over the

Texture Surface n CGVR Add Visual Detail to Surfaces of 3 D Objects With

Overview n CGVR Texture Mapping Methods Mapping n Filtering n n Texture Mapping Applications

Texture Mapping n CGVR Texture mapping methods Mapping n Filtering n n Texture mapping

Texture Filtering n CGVR Must Sample Texture to Determine Color at Each Pixel in

Texture Filtering n CGVR Ideally, Use Elliptically Shaped Convolution Filters n In practice, use

Texture Filtering n CGVR Size of Filter Depends on Projective Warp n Can prefiltering

Mip Maps n CGVR Keep Textures Pre-filtered at Multiple Resolutions For each pixel, linearly

Texture Filtering n CGVR Aliasing is a Problem Point Sampling cgvr. korea. ac. kr

Modulation Texture Map Texture Values to Scale Factor Wood Texture n CGVR Texture Value

Illumination Mapping n CGVR Map Texture Values to Surface Material Parameter n n n

Bump Mapping n CGVR Map Texture Values to Perturbations of Surface Normals cgvr. korea.

Bump Mapping n CGVR Apply a perturbation function to the surface normal cgvr. korea.

Environmental Mapping n CGVR Map Texture Values to the Environment Map Surface Pixel Projection

Image-Based Rendering n CGVR Map Photographic Textures to Provide Details for Coarsely Detailed Polygonal

Nonphotorealistic Rendering cgvr. korea. ac. kr CGVR Graphics Lab @ Korea University

Summary n CGVR Texture mapping methods Mapping n Filtering n n Texture mapping applications

Slides: 38

Download presentation

Graphics Creating Virtual World II CSE 425 Virtual Reality 2001. 4. 4 cgvr. korea. ac. kr Graphics Lab @ Korea University

Overview n CGVR Rendering 3 D Rendering Pipeline n Global Illumination n n Texture Mapping cgvr. korea. ac. kr Graphics Lab @ Korea University

Rendering n 3 D Rendering Pipeline n n n n CGVR Modeling transformations Viewing transformations Hidden surface removal Illumination, shading, and textures Scan conversion, clipping Hierarchical scene graphics Open. GL A ray–traced scene Global illumination Ray tracing n Radiosity n cgvr. korea. ac. kr Nave of Chartres Cathedral rendered with a progressive refinement radiosity Graphics Lab @ Korea University

Introduction to Rendering n CGVR Visual Realism Hidden surface removal n Lights and materials n Shading algorithm n n Rendering A critical process in CG n Quite time-consuming n o “Toy Story” - between an hour to 24 hours cgvr. korea. ac. kr Graphics Lab @ Korea University

3 D Rendering Pipeline CGVR 3 D Geometric Primitives Modeling Transformation Lighting Viewing Transformation Projection Transformation This is a pipelined sequence of operations to draw a 3 D primitive into a 2 D image Clipping Scan Conversion Image cgvr. korea. ac. kr Graphics Lab @ Korea University

3 D Rendering Pipeline CGVR 3 D Geometric Primitives Modeling Transformation Lighting Transform into 3 D world coordinate system Illuminate according to lighting and reflectance Viewing Transformation Transform into 3 D camera coordinate system Projection Transformation Transform into 2 D camera coordinate system Clipping Clip primitives outside camera’s view Scan Conversion Draw pixels (texture mapping, hidden surface removal, etc) Image cgvr. korea. ac. kr Graphics Lab @ Korea University

Hidden Surface Removal n CGVR Motivation I n Surfaces may be back-facing Back-Facing Polygon Viewer n Surfaces may be occluding Viewer cgvr. korea. ac. kr Occluding Polygon Occluded Polygon Graphics Lab @ Korea University

Hidden Surface Removal (cont. ) n CGVR Motivation II n Surfaces may be overlapped n Surfaces may be intersected cgvr. korea. ac. kr Graphics Lab @ Korea University

Hidden Surface Removal (cont. ) n CGVR Algorithms n n n Back-face detection Depth sort Ray casting Scan-line Z-buffer Area subdivision cgvr. korea. ac. kr Graphics Lab @ Korea University

Modeling Light Sources CGVR n n n Describes the intensity of energy Leaving a light source Arriving at location From direction With wavelength Light cgvr. korea. ac. kr Graphics Lab @ Korea University

Light Source Models n CGVR Simple mathematical models: Point light n Directional light n Spot light n cgvr. korea. ac. kr Graphics Lab @ Korea University

Modeling Surface Reflectance CGVR n Describe the amount of incident energy n Arriving from direction n Leaving in direction n With wavelength n Surface cgvr. korea. ac. kr Graphics Lab @ Korea University

Reflectance Model n CGVR Simple analytic model: Diffuse reflectance + n Specular reflectance + n Emission + n Ambient n Surface cgvr. korea. ac. kr Graphics Lab @ Korea University

Emission & Ambient n Emission n n CGVR Represents light emanating directly from polygon Ambient n Represents reflection of all indirect illumination cgvr. korea. ac. kr Graphics Lab @ Korea University

Reflectance Model n CGVR Simple analytic model: Diffuse reflectance + n Specular reflectance + n Emission + n Ambient n Surface cgvr. korea. ac. kr Graphics Lab @ Korea University

Shading CGVR Determine a color for each filled pixel n Polygon Shading n Flat shading n Gouraud shading n Phong shading n n Global Shading Ray tracing n Radiosity n cgvr. korea. ac. kr Graphics Lab @ Korea University

Ray Tracing n CGVR Technique for global reflection and transmission Visible-surface detection n Shadow effects n Transparency n Multiple light-source illumination n n High realistic vs. computation time cgvr. korea. ac. kr Graphics Lab @ Korea University

Radiosity n Energy/unit area leaving a surface n The method for describing diffuse reflections n n CGVR Consider radiant energy transfers between surfaces Basic Radiosity Model n Consider the radiant-energy interactions between all surfaces in a scene Differential amount of radiant energy d. B leaving each surface point o Summing the energy contributions over all surfaces cgvr. korea. ac. kr Graphics Lab @ Korea University

Overview n CGVR Rendering 3 D Rendering Pipeline n Global Illumination n n Texture Mapping cgvr. korea. ac. kr Graphics Lab @ Korea University

3 D Rendering Pipeline 3 D Primitives CGVR 3 D Modeling Coordinates Model Transformation 3 D World Coordinates Lighting 3 D World Coordinates Viewing Transformation 3 D Viewing Coordinates Projection Transformation 2 D Projection Coordinates Clipping 2 D Projection Coordinates Viewport Transformation Texture Mapping 2 D Device Coordinates Scan Conversion Image cgvr. korea. ac. kr 2 D Device Coordinates Graphics Lab @ Korea University

Texture Mapping n CGVR Texture mapping Superimpose a completely independent twodimensional image over the surface of the object n Vitality to models and can provide great looking visual cues n cgvr. korea. ac. kr Graphics Lab @ Korea University

Texture Surface n CGVR Add Visual Detail to Surfaces of 3 D Objects With Surface Texture Polygonal Model cgvr. korea. ac. kr Graphics Lab @ Korea University

Overview n CGVR Texture Mapping Methods Mapping n Filtering n n Texture Mapping Applications n n n Modulation textures Illumination mapping Bump mapping Environment mapping Image-based rendering Non-photorealistic rendering cgvr. korea. ac. kr Graphics Lab @ Korea University

Texture Mapping n CGVR Texture mapping methods Mapping n Filtering n n Texture mapping applications n n n Modulation textures Illumination mapping Bump mapping Environment mapping Image-based rendering Non-photorealistic rendering cgvr. korea. ac. kr Graphics Lab @ Korea University

Texture Filtering n CGVR Must Sample Texture to Determine Color at Each Pixel in Image y s ys x t xs z cgvr. korea. ac. kr Graphics Lab @ Korea University

Texture Filtering n CGVR Ideally, Use Elliptically Shaped Convolution Filters n In practice, use rectangles Texture Screen cgvr. korea. ac. kr Graphics Lab @ Korea University

Texture Filtering n CGVR Size of Filter Depends on Projective Warp n Can prefiltering images Mip maps o Summed area tables o s ys s Texel ys Texel Pixel t Magnification cgvr. korea. ac. kr Pixel xs t xs Minification Graphics Lab @ Korea University

Mip Maps n CGVR Keep Textures Pre-filtered at Multiple Resolutions For each pixel, linearly interpolate between two closest levels (e. g. , trilinear filtering) n Fast, easy for hardware n cgvr. korea. ac. kr Graphics Lab @ Korea University

Texture Filtering n CGVR Aliasing is a Problem Point Sampling cgvr. korea. ac. kr Area Filtering Graphics Lab @ Korea University

Overview n CGVR Texture mapping methods Mapping n Filtering n n Texture mapping applications n n n Modulation textures Illumination mapping Bump mapping Environment mapping Image-based rendering Non-photorealistic rendering cgvr. korea. ac. kr Graphics Lab @ Korea University

Modulation Texture Map Texture Values to Scale Factor Wood Texture n CGVR Texture Value cgvr. korea. ac. kr Graphics Lab @ Korea University

Illumination Mapping n CGVR Map Texture Values to Surface Material Parameter n n n KA KD KS KT n cgvr. korea. ac. kr Graphics Lab @ Korea University

Bump Mapping n CGVR Map Texture Values to Perturbations of Surface Normals cgvr. korea. ac. kr Graphics Lab @ Korea University

Bump Mapping n CGVR Apply a perturbation function to the surface normal cgvr. korea. ac. kr Graphics Lab @ Korea University

Environmental Mapping n CGVR Map Texture Values to the Environment Map Surface Pixel Projection onto Environment Map Pixel Area Projection Reference Point cgvr. korea. ac. kr Graphics Lab @ Korea University

Image-Based Rendering n CGVR Map Photographic Textures to Provide Details for Coarsely Detailed Polygonal Model cgvr. korea. ac. kr Graphics Lab @ Korea University

Nonphotorealistic Rendering cgvr. korea. ac. kr CGVR Graphics Lab @ Korea University

Summary n CGVR Texture mapping methods Mapping n Filtering n n Texture mapping applications n n n Modulation textures Illumination mapping Bump mapping Environment mapping Image-based rendering Non-photorealistic rendering cgvr. korea. ac. kr Graphics Lab @ Korea University