Adding Surface Detail

1. Adding Surface Detail 고려대학교 컴퓨터 그래픽스 연구실

2. 3D Rendering Pipeline 3D Primitives 3D Modeling Coordinates Model Transformation 3D World Coordinates Lighting 3D World Coordinates Viewing Transformation 3D ViewingCoordinates 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

3. Overview • Texture mapping methods • Mapping • Filtering • Texture mapping applications • Modulation texture • Bump mapping • Environment mapping

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

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

6. 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 Image Space Texture Space Object Space

7. 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

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

9. Texture Mapping Linear Interpolation of Texture Coordinate Corrected Interpolation

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

11. Texture Filtering • To avoid aliasing problem Corrected Result Point Sampling

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

13. MipMaps • Keep textures prefiltered at multiple resolutions • For each pixel • Linearly interpolate between two closest levels • Trilinear filtering • Fast and easy for hardware

14. Overview • Texture mapping methods • Mapping • Filtering • Texture mapping applications • Modulation texture • Bump mapping • Environment mapping

15. Modulation Texture Texture Shaded Color Texture Value

16. Bump Mapping • Perturbate surface normals

17. Bump Mapping

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

19. Summary • Texture mapping methods • Mapping • Filtering • Texture mapping applications • Modulation textures • Bump mapping • Environment mapping

20. Wireframe

21. Ambient Illumination Only

22. Flat Shaded Polygonswith Diffuse Reflection

23. Gouraud Shaded Polygonswith Diffuse Reflection

24. Gouraud Shaded Polygonswith Specular Reflection

25. Phong Shaded Polygonswith Specular Reflection

26. Curved Surfaceswith Specular Reflection

27. Improved Illumination Modelwith Multiple Lights

28. Texture Mapping

29. Bump Mapping

30. Reflection Mapping