Homework 3 – Textures
1. Considering the following chessboard texture with (u,v) coordinates:
(0,1) (1,1)
rmblkans
opopopop
0Z0Z0Z0Z
Z0Z0Z0Z0
0Z0Z0Z0Z
Z0Z0Z0Z0
POPOPOPO
SNAQJBMR
(0,0) (1,0)
(a) Draw the approximate mapping on each quad if they were textured using the
above image.
(0.75, 0.125) (0.875, 0.125)
(0.75, 0.25) (0.875, 0.25)
u,v = 0.5, 0.875 u,v = 0.5, 1.0
u,v = 0.625, 0.875 u,v = 0.625, 1.0
(b) Label the (u,v) texture coordinates for each of the 4 vertices that would result
in the image below (just write them next to the corner of each square).
l
p OP
QJ
PO
MR
2. Describe how and when one could use Spherical Parameterization to map a texture
onto a 3D model.
1
1. Considering the following chessboard texture with (u,v) coordinates:
(0,1) (1,1)
rmblkans
opopopop
0Z0Z0Z0Z
Z0Z0Z0Z0
0Z0Z0Z0Z
Z0Z0Z0Z0
POPOPOPO
SNAQJBMR
(0,0) (1,0)
(a) Draw the approximate mapping on each quad if they were textured using the
above image.
(0.75, 0.125) (0.875, 0.125)
(0.75, 0.25) (0.875, 0.25)
u,v = 0.5, 0.875 u,v = 0.5, 1.0
u,v = 0.625, 0.875 u,v = 0.625, 1.0
(b) Label the (u,v) texture coordinates for each of the 4 vertices that would result
in the image below (just write them next to the corner of each square).
l
p OP
QJ
PO
MR
2. Describe how and when one could use Spherical Parameterization to map a texture
onto a 3D model.
1
3. In texture mapping, what is the difference between magnification and minification?
4. We textured a floor in our world and wish it looked like the left image, instead we
got the right image, with speckled Moire patterns in the back and Jaggies in the
front.
(a) Explain why these Moire patterns appear and how to fix them.
(b) Explain why these Z0Z0Z0Z0appear and how to fix them.
5. What is the following fragment shader doing?
varying vec2 uv;
uniform sampler2D tex;
uniform vec4 baseColor;
void main() {
vec4 texColor = texture2D(tex, uv);
gl_FragColor = 0.5 * texColor + 0.5 * base Color
