Adding Surface Detail 고려대학교 컴퓨터 그래픽스 연구실

3D Rendering Pipeline Surface details can be added... 3D Primitives 3D Modeling Coordinates Model Transformation 3D World Coordinates Lighting 3D World Coordinates Viewing Transformation 3D Viewing Coordinates Projection Transformation Surface details can be added... 2D Projection Coordinates Clipping 2D Projection Coordinates Viewport Transformation 2D Device Coordinates Scan Conversion 2D Device Coordinates Image

Overview Texture mapping methods Texture mapping applications Mapping Filtering Texture mapping applications Modulation texture Bump mapping Environment mapping

Texture Surface Add visual detail to surfaces of 3D objects With Surface Texture Polygonal Model

Texture Mapping 2D projective transformation Texture coordinate system (s, t) to Device coordinate system (x, y)

Viewing and Projection Textures Color variation in interior of 3D polygon When scan converting a polygon Vary pixel colors according to values fetched from a texture y ys t Texture-Surface Transformation Viewing and Projection Transformation x s xs z Texture Space Object Space Image Space

Texture Mapping Steps: Define texture Specify mapping from texture to surface Lookup texture values during scan conversion (0, 1) (1, 0) t v y s u (0, 0) x Texture Coordinate System Modeling Coordinate System Device Coordinate System

Texture Mapping Scan conversion Interpolate texture coordinates Distortion due to the bilinear interpolation Subdivide the polygon into smaller ones α β  (u1, v1) (u3, v3) (u2, v2)

Corrected Interpolation Texture Mapping Linear Interpolation of Texture Coordinate Corrected Interpolation

Texture Sampling To determine color at each pixel in image y ys t s x xs z

Texture Filtering To avoid aliasing problem Point Sampling Corrected Result

Texture Filtering Ideally, use elliptically shaped convolution filters In practice, use rectangles Texture Space Screen Space

Mip Maps Keep textures prefiltered at multiple resolutions For each pixel Linearly interpolate between two closest levels Trilinear filtering Fast and easy for hardware

Overview Texture mapping methods Texture mapping applications Mapping Filtering Texture mapping applications Modulation texture Bump mapping Environment mapping

Modulation Texture Texture Shaded Color Texture Value

Bump Mapping Perturbate surface normals

Bump Mapping

Environment Mapping Map texture values to the environment map Surface Pixel Projection onto Environment Map Pixel Area Projection Reference Point

Summary Texture mapping methods Texture mapping applications Mapping Filtering Texture mapping applications Modulation textures Bump mapping Environment mapping

Wireframe

Ambient Illumination Only

Flat Shaded Polygons with Diffuse Reflection

Gouraud Shaded Polygons with Diffuse Reflection

Gouraud Shaded Polygons with Specular Reflection

Phong Shaded Polygons with Specular Reflection

Curved Surfaces with Specular Reflection

Improved Illumination Model with Multiple Lights

Texture Mapping

Bump Mapping

Reflection Mapping