Texture Mapping We can improve the realism of graphics models by mapping a texture pattern (image) onto the modeled object surface. We refer to this technique as texture mapping or pattern mapping. Adding texture mapping to polygonal models

Coordinate Refence Systems Texture mapping approaches Texture scanning Map the texture pattern to object surface. Map to project to the plane Pixel-order scanning Map pixel areas onto object surfaces. Map to texture space

Mapping u = fu(s,t) = aus + but + cu v = fv(s,t) = avs + bvt + cv

Example Surface Parameters u =  ; 0 <  < 90 v = z ; 0 < z < 1 The parametric representation of the surface x = r cos(u) ; y = r sin(u); z = v Map the array to the surface u = s*90 ; v = t Select the viewing position and perform the inverse of the viewing transformation from from pixel coordinate to the cylinder surface.

MipMaps Large texture need more memory space and more time to render. Different resolution texture Close regions have high resolution textures. Far regions have low resolution textures Level-0 Level-1 Level-2

Bump Mapping Bump Mapping is used to model the surface roughness. Bump mapping usually achieved by applying a perturbation function

OpenGL Textures Texture width and height are power of 2 Allows border for textures Several image packing strategies Right now, handles 1D and 2D textures Could wrap or clamp textures

Code Exampe // During Initialization stage glBindTexture (GL_TEXTURE_2D, 13); glPixelStorei (GL_UNPACK_ALIGNMENT, 1); glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT); glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT); glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST); glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); */ glTexParameteri (GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); glTexEnvf (GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE); glTexImage2D (GL_TEXTURE_2D, 0, GL_RGB, img_width, img_height, 0, GL_RGB, GL_UNSIGNED_BYTE, data);

Code Example //At Display glEnable (GL_TEXTURE_2D); glBindTexture (GL_TEXTURE_2D, 13); // Start Geometry glTexCoord2f (0.0,0.0); glVertex3f(5.0, 7.1, 3.6);