1. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003 Texture Mapping

2. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003 Today’s Short Film by

3. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003 Announcement Remaining paper presentations on and after April 29. –Please pick a date and select a topic from the reading list.

4. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003 Texture Mapping The simplest form: like wrapping a picture on an object. Texture: 2D image or a simple pattern (like a checkerboard) Surface: could be any shape

5. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003 Examples Almost trivial: Rectangular surface A little bit harder: a Coke can Cube? Sphere? Curve surface?

6. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003 Texture Coordinates The mapping between surface points to image pixels is defined by assigning texture coordinates to vertices of a surface. Many surfaces have a natural “parameter space”

7. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003 Procedural Texture A simple example: checkerboard. Solid texture. Example: wood carving. More advacned: Perlin noise.

8. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003 Bump Map and Displacement Map Examples: –Golf ball –Figure 8.10 of Watt’s book Bump Map vs. Displacement Map: –Bump Map: only the looks change –Displ. Map: the actual surface points change.

9. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003

10. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003 Environment Map

11. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003 Texture Mapping and Polygon Rasterization Problems of linearly interpolating texture coordinates in screen space. –Similar problems in the interpolations of colors for Gouraud shading and normals for Phong shading. Problems in antialiasing –Expanding and shrinking

12. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003

13. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003 Polygon Subdivision

14. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003 Perspective Correction Dividing the texture coordinates by w Linearly interpolating (u/w, v/w, 1/w) At each pixel, dividing (interpolated) u/w and v/w by (interpolated) 1/w. Reference: Heckbert & Moreton “Interpolation for Polygon Texture Mapping and Shading”

15. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003 Using Textures in OpenGL Directly from SG2001 Course 54:

16. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003

17. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003

18. CS6500 Adv. Computer Graphics © Chun-Fa Chang, Spring 2003 Projective Texture Mark Segal, et al., “Fast shadows and lighting effects using texture mapping”. SIGGRAPH 92Fast shadows and lighting effects using texture mapping Cass Everitt, “Projective Texture Mapping” NVIDIA SDK White Paper.Projective Texture Mapping Figure 1. Two different views of a smiley face texture projected onto the scene.