CS488 Vision and Light Luc R ENAMBOT 1 Outline We talked about - - PowerPoint PPT Presentation
CS488 Vision and Light Luc R ENAMBOT 1 Outline We talked about how to take 2D and 3D scenes and draw them on a 2D surface We will be discussing how to make these images more interesting Topics light, illumination, colour,
Luc RENAMBOT
1
and draw them on a 2D surface
more interesting
2
and the nature of human vision
sophisticated concepts of illumination and shading
3
the lens onto the retina at the back of the eye
cornea is close to water, and has the same index of refraction as
light is not refracted, but it is refracted if we are not in water
4
direction of a wave front at an interface between two dissimilar media so that the wave front returns into the medium from which it
5
direction of a wave due to a change in its velocity
when a wave passes from one medium to another
6
lens hits the fovea (or Macula).
sensitivity
7
and quickly taper off around the retina
the fovea, or approximately at the center of out field of vision
center of the field of view. However, we are very sensitive to motion on the periphery of our vision, so we can see movement even if we can't see what is moving
8
degrees on both sides of the fovea, but almost none are at the fovea itself
to see something dim you can not look directly at it
9
degrees away from the fovea which connects your eye to your brain
cones and no rods. We can not see anything at this point though we are so used to this that we do not notice it unless we try to see the blind spot
10
11
http://serendip.brynmawr.edu/bb/blindspot1.html
12
a dark area, say into a movie theatre?
illumination levels provide all the stimulous
don't have enough illumination to do much good, and the rods take time to desaturate before they can be useful in the new lower illumination environment
13
very sensitive, so dark adjust for about 20 minutes before going stargazing
intensities, we can not see colour in dim light as
in the dark (it appears black)
14
a LCD screens to creating an illusion of 3D on a flat screen
15
16
17
18
19
1 as white
intensity) has a logarithmic scale, not a linear scale
20
backlight
light reflection within the tube
the dynamic range
21
and a maximum intensity of 1, the ratio of succeeding intensities is
intensities are:
0.1 0.13 0.17 0.21 0.28 0.36 0.46 0.59 0.77 1.0
0.1 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.0
22
1 n
n−j n
smooth continuous tone depends on the dynamic range of the device. The human eye can not distinguish intensities with a ratio of less than 1.01.
and want to find n:
23
1 n
following
24
from grey
25
in the human eye, one attuned to red, one to green, and one to blue (Young and Helmholtz)
from 400nm - 700nm
26
27
eye can see using an RGB display
the eye can see using photographic film (though it can display a larger part of the visible spectrum than a monitor)
28
developed in 1931
cone, by normalizing we reduce the cone to a plane (the X + Y + Z = 1 plane)
(hue) and saturation only
luminances are mapped onto the same point
possible colors as color also depends on luminance (lightness or brightness)
29
blue) to create all of the possible colors that we can see
primary colors X, Y, and Z are defined so that you can add X and Y and Z together to get all
Y, and Z are not be red, green, and blue and the color matching functions (the curves) of X, Y, and Z are not the curves of red, green, and blue.
should see section 13.2.2 (p579)
30
X Y R G B
31
Y R G B W
32
between those 2 points are mixtures of those two colors.
white-light center, whose mixture yields the white-light center.
R, G, and B
compare the gamuts of different devices on the same diagram
33
YUV
34
colours Red Green Blue
0 to 1
to form the final color
35
(0,0,0) -> black (1,1,1) -> white (1,0,0) -> red (0,1,0) -> green (0,0,1) -> blue (1,1,0) -> yellow (1,0,1) -> magenta (0,1,1) -> aqua
36
Yellow each of which ranges from 0 to 1, which are subtracted from white to form the final color
blue
green
37
(1,0,1) -> green (1,1,0) -> blue
(0,1,0) -> magenta (1,0,0) -> aqua
38
39
CMY
Y)
Ycmy - K
40
broadcasts
shown on black and white TVs
information
41
Y I Q = 0.299 0.587 0.114 0.596 −0.275 −0.321 0.212 −0.528 0.311 ∗ R G B
YUV color space
analog component video and its digital child
42
YUV
Saturation Value (Brightness)
effectively use color, and many, many examples of how not to use color
43
44
45
Normal Deuteranopia (Daltonism) Tritanopia Protanopia
dangerous tool
physiological issues we looked at with the optical illusions, there is a lot of cultural baggage associated with color
you are doing (e.g.. scientific visualizations) you need to learn about color or work with someone who knows about color
46
the optical illusions at the beginning work, and how we can play 'Doom' and get a sense
well with only these 2D cues
47
48
that are further away
us it gets larger in our retina but we do not perceive it getting bigger. We understand that it isn't changing its size as it moves
are the same size and one appears to be smaller than the other then the smaller one is further away
49
the vanishing point as they go off in the distance
move 'more' or 'faster' than objects that are further away.
the air make objects that are further away appear less distinct
50
You can only discern textures when an
uniform
reasons
51
differential size
motion parallax
52
53