G11: Texture Mapping Flashcards
What is a texture in computer graphics?
An image representing detailed surface patterns; used to efficiently store and render surface appearance.
What are texels?
Texture elements—the pixels of a texture image.
What is texture mapping?
The process of projecting a 2D image (texture) onto a 3D surface.
Name three basic projection methods for texture mapping.
Planar projection
Cylindrical projection
Spherical projection
What issue can arise with simple projections?
Distortions, especially at poles or when the intermediate object and target surface differ.
What is UV mapping?
Mapping 3D model surface coordinates to a 2D domain (UV space) for texture application.
What is UV unwrapping?
The process of flattening a 3D model’s surface into a 2D space for texture painting.
Why is perspective-correct interpolation needed in texture mapping?
Because interpolation in screen space can distort textures under perspective projection.
How is perspective-correct interpolation done?
Interpolate u/z, v/z, and 1/z
Invert and multiply to get the correct texture coordinates
What is the problem of magnification in texture mapping?
A screen pixel is much smaller than a texel, leading to over-sampling and artifacts.
How is magnification handled?
By using bilinear interpolation to blend the values of the four surrounding texels.
What is the bilinear interpolation formula?
(1−t)⋅[(1−s)t00+st10]+t⋅[(1−s)t01+st11]
What is minification in texture mapping?
When a screen pixel covers many texels, leading to under-sampling and aliasing.
How is minification handled?
By prefiltering textures using MIP maps to average over a pixel’s footprint.
What are MIP maps?
A set of down-sampled textures (image pyramid), with each level having half the resolution of the previous.
How is the appropriate MIP level chosen?
l=log2(max(dx^2,dy^2))
Where dx and dy are distances between neighboring pixel samples.
What does MIP stand for?
Multum In Parvo (Latin) — meaning “much in little.”
