1. Texture Mapping
Jung Lee

2. *Edwin Catmull, Ph.D. Thesis, 1974
Texture Mapping*
Adds visual detail to surfaces of 3D objects

3. Texture Mapping Example

4. Texture and Texel Texel : Texture Element Texture Coordinates (s, t)
GPUs can handle usually 2m x 2n texels
Where m and n are nonnegative integers
Texture Coordinates (s, t)

5. 2D Texture Space Continuous (s, t) Coordinate Space [0, 1]
For mapping it into a discrete texture image space
[Texture Map]
[2D Texture Image]

6. Texture Mapping Overview
1. Define a texture image
2. Specify mapping from the texture to surface
Texture coordinate
3. Lookup texture values during scan conversion
(0, 1)
(1, 0) t v s u
(0, 0) y x

7. Texture Value Lookup Bilinearly interpolate texture coordinates
In the scan conversion step α β 
(u1, v1)
(u3, v3)
(u2, v2)

8. Texture Modulation
Texture
Shaded
Color
Texture
Shading

9. Bump Mapping Perturbs surface normal vectors Normal Information
So called ‘normal mapping’
Normal Information
Normal information can be stored in a RGB image
Convert (x, y, z) to (R, G, B)

10. Bump Mapping Example (1/5)
[Bump Mapped Sphere]

11. Bump Mapping Example (2/5)

12. Bump Mapping Example (3/5)

13. Bump Mapping Example (4/5)

14. Bump Mapping Example (5/5)
4M Triangles
500 Triangles

15. Displacement Mapping
Modifying the actual surface geometry

16. How to Assign Normal Vectors in OpenGL
Face Normal Vector
Vertex Normal Vector
N(a, b, c)
glBegin(GL_POLYGON);
glNormal3f(a, b, c);
glVertex3f(x1, y1, z1);
glVertex3f(x2, y2, z2);
glVertex3f(x3, y3, z3);
glEnd();
P1(x1, y1, z1)
P2(x2, y2, z2)
P3(x3, y3, z3)
N1(a1, b1, c1)
glBegin(GL_POLYGON);
glNormal3f(a1, b1, c1);
glVertex3f(x1, y1, z1);
glNormal3f(a2, b2, c2);
glVertex3f(x2, y2, z2);
glNormal3f(a3, b3, c3);
glVertex3f(x3, y3, z3);
glEnd();
N2(a2, b2, c2)
P1(x1, y1, z1)
N3(a3, b3, c3)
P2(x2, y2, z2)
P3(x3, y3, z3)

17. Environment Mapping Maps a surrounding environment texture
Around a surface of an object
To approximate effects like reflection or refraction
View dependant
Due to reflective mapping process
Not need the texture coordinates
Since surface normals are used to map the environment texture
Cubic Environment Mapping
Spherical Environment Mapping

18. Cubic Environment Mapping

19. Environment Mapping Example