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ECS 175 Fall 2019 - Assignment 1 Manual
Author: lxylxy123456 (https://github.com/lxylxy123456/)

Run: run the following line, make sure `test_scene` is in same directory
    ./Project1

Switch between DDA (default) and Bresenham
    1. Right click anywhere on the "glut demo" screen
    2. Click "Bresenham / DDA" button
    3. (or you can press keyboard "B" instead of doing 1 and 2)
    4. Current algorithm displayed on stdout

Switch between Draw Only Edge (default) and Rasterization
    1. Right click
    2. Click "Rasterization / Draw Only Edge" button
    3. (or press keyboard "f" instead of 1 and 2)

Clipping
    Clipping
        1. Right click
        2. Click "Clip" on menu
        3. (or press keyboard "c" instead of 1 and 2)
        4. Drag your mouse in the screen from point A (mouse down) to point B
            (mouse up). A and B are two corners of the clip window.
    Unclipping
        1. Right click
        2. Click "No Clip" on menu
        3. (or use keyboard "Shift + C")

Hide / Show a polygon
    1. Right click
    2. Hide / Show -> Hide / show (ID of polygon)
    3. (or you can press "0" for hide / show polygon 0, "1" for polygon 1, ...)

Translation
    1. Right click
    2. Translation -> Translate (ID of polygon)
    3. Drag your mouse through the screen. This will define translation vector.
    4. `test_scene` will be automatically updated, same below

Rotation
    1. Right click
    2. Rotation -> Rotate (ID of polygon)
    3. Drag your mouse through the screen. The two points you drag and the
        centroid of the polygon will define start line and end line of rotation.
        (Image you are editing a shape using Word / Google Docs, same below)

Scaling
    1. Right click
    2. Scaling -> Scale (ID of polygon)
    3. Drag your mouse through the screen. The two points you drag and the
        centroid of the polygon will define start and end size of the polygon.

Quit
    1. Right click
    2. Quit

Auto rotate (extra feature)
    Press "Shift + K" on keyboard
    Press again to cancel