Post by Craig Treptow on Dec 28, 2018 20:32:29 GMT
Hi there. I've really been enjoying my time with the book so far, but am now feeling really dumb, or that I missed something crucial in the book.
I'm in the initial Canvas section, where I read:
Note that color components that would be greater than 255 are limited (or clamped) to 255, and components that would be less than 0 are clamped to 0.
...and then this test description:
Scenario: Constructing the PPM pixel data
Given c ← canvas(5, 3)
And c1 ← color(1.5, 0, 0)
And c1 ← color(1.5, 0, 0)
And c2 ← color(0, 0.5, 0)
And c3 ← color(-0.5, 0, 1)
When write_pixel(c, 0, 0, c1)
When write_pixel(c, 0, 0, c1)
And write_pixel(c, 2, 1, c2)
And write_pixel(c, 4, 2, c3)
And ppm ← canvas_to_ppm(c)
Then lines 4-6 of ppm are
Then lines 4-6 of ppm are
"""
255 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 128 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 255
"""
255 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0 0 0 0 0 128 0 0 0 0 0 0 0
0 0 0 0 0 0 0 0 0 0 0 0 0 0 255
"""
So somehow, 1.5 and 1 are mapped to 255, 0.5 to 128, and -0.5 to 0. There was no need to do any clamping process on anything but the -0.5, right? Was this clamping algorithm given somewhere? I think that's what I don't understand right now.
Any help is appreciated.
- Craig
