Graphics Texture Mapping cgvr korea ac kr 1

Graphics Texture Mapping 고려대학교 그래픽스 연구실 cgvr. korea. ac. kr 1 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 2 D Device Coordinates Image cgvr. korea. ac. kr 2 Graphics Lab @ Korea University

Textures n CGVR Color variation in interior of 3 D polygon n When scan converting a polygon o Vary pixel colors according to values fetched from a texture y s x t Texture z cgvr. korea. ac. kr ys 3 Surface Image xs 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 4 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 5 Graphics Lab @ Korea University

Texture Mapping CGVR Steps: n Define texture n Specify mapping from texture to surface n Lookup texture values during scan conversion n (0, 1) s (1, 0) v t (0, 0) Texture Coordinate System cgvr. korea. ac. kr u Modeling Coordinate System 6 y x Device Coordinate System Graphics Lab @ Korea University

Texture Mapping CGVR When scan converting n Device coordinate system (x, y) n Modeling coordinate system (u, v) n Texture image (t, s) n (0, 1) s (1, 0) v t (0, 0) Texture Coordinate System cgvr. korea. ac. kr u Modeling Coordinate System 7 y x Device Coordinate System Graphics Lab @ Korea University

Texture Mapping n CGVR 2 D projective transformation Texture coordinate system (t, s) to n Device coordinate system (x, y) n cgvr. korea. ac. kr 8 Graphics Lab @ Korea University

Texture Mapping n CGVR Scan conversion Interpolate texture coordinates n Distortion due to bilinear interpolation approximation n Cut polygons into smaller ones, or o Perspectively divide at each pixel o (u 1, v 1) α γ β (u 2, v 2) cgvr. korea. ac. kr 9 (u 3, v 3) Graphics Lab @ Korea University

Texture Mapping Linear Interpolation of Texture Coordinate cgvr. korea. ac. kr 10 CGVR Corrected Interpolation with Perspective Divide 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 11 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 12 Graphics Lab @ Korea University

Texture Filtering n CGVR Aliasing is a problem Point Sampling cgvr. korea. ac. kr 13 Area Filtering 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 14 Graphics Lab @ Korea University

Texture Filtering n CGVR Size of filter depends on projective warp n Prefiltering images Mip maps o Summed area tables o s ys s Texel ys Texel Pixel t xs Magnification cgvr. korea. ac. kr Pixel 15 t xs Minification Graphics Lab @ Korea University

Mip Maps n CGVR Keep textures prefiltered at multiple resolutions For each pixel, linearly interpolate between two closest levels (e. g. , trilinear filtering) n Fast and easy for hardware n cgvr. korea. ac. kr 16 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 17 Graphics Lab @ Korea University

Modulation Texture Map Texture Values to Scale Factor Wood Texture n CGVR Texture Value cgvr. korea. ac. kr 18 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 19 Graphics Lab @ Korea University

Bump Mapping n CGVR Map Texture Values to Perturbations of Surface Normals cgvr. korea. ac. kr 20 Graphics Lab @ Korea University

Bump Mapping cgvr. korea. ac. kr 21 CGVR 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 22 Graphics Lab @ Korea University

Image-Based Rendering n CGVR Map Photographic Textures to Provide Details for Coarsely Detailed Polygonal Model cgvr. korea. ac. kr 23 Graphics Lab @ Korea University

Nonphotorealistic Rendering cgvr. korea. ac. kr 24 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 25 Graphics Lab @ Korea University