Lecture 12: Textures – Review Questions

Describe conceptually how texture can be applied to a triangle in a scene. Draw a
sketch to illustrate your answer.

Suppose you have a 800x600 image of a world map that is a Mercator projection
of the world. In other words, the map is laid out with latitude coordinates that
range from -90 degrees to 90 degrees and longitude coordinates from -180
degrees to 180 degrees. Compute the complete mapping from a latitude /
longitude value to a pixel element in the texture map. Reference pages 306 and
307 in the handout (Ch12) for additional details.

Suppose your resulting texture coordinates are (56.2, 73.6). Give an algorithm
that uses bilinear interpolation to compute a color from the pixels surrounding this
point. What are the relative contributions of all pixels surrounding this point to
the final color computed for this point? Draw a diagram to illustrate your
assumptions (e.g., what are the coordinates of the pixel centers of all neighboring
pixels).

Suppose you have texture coordinates (u,v) for each vertex of a triangle. Explain
how barycentric coordinates are used to determine the color at each pixel of a
textured triangle.

What are mipmaps and why do we use them?

Texture maps can be used to modify a wide variety of different values that may
vary over the surface of an object. List at least five different parameter values
that may be controlled using a texture map (i.e., five different ways in which
texture maps can be used to control object appearance).

What is a bump map? a normal map? a displacement map? an environment
map?