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ECS 175 Fall 2019 - Assignment 4 Manual
Author: lxylxy123456 (https://github.com/lxylxy123456/)

GUI using: https://github.com/libglui/glui

Run
    (The program will always try to read the file `test_scene` for curves)
    ./Project4

Note
    All feedback information will appear at lower part of screen as text. 
    All Bezier curves are colored blue
    Most B-spline curves are colored green; the selected one is colored orange.

Show / hide control vertex / polygon
    Use checkbox "Show / hide control vertex" and "Show / hide control polygon"
    When operating on curves that involves clicking on screen (e.g. add, insert,
     move, delete vertex / curve), please make sure control vertices and control
     polygons are visible.

Operation on curve
    Add a curve
        1. Specify number of endpoints (input or adjust up / down)
        2. Specify whether draw B-spline or Bezier curve
        3. Press "Add curve"
        4. Click on screen for each position of control points
        5. Note: for B-spline curve, the order of new curve is always 2
    Delete a curve: 
        1. Press "Delete curve"
        2. Click on a CONTROL POINT of a curve on screen
    Hide one curve: 
        1. Press "Hide one curve"
        2. Click on a CONTROL POINT of a curve on screen
    Show only one curve: 
        1. Press "Show only one curve"
        2. Click on a CONTROL POINT of a curve on screen
        3. All other curves will be hidden, the one selected will remain there
    Show all curves: 
        0. This is the only way to show a hidden curve
        1. Click on "Show all curves"
        2. All curves will be shown
        3. Sorry I cannot find a way to select a hidden curve
    Convert between B-spline curves / Bazier curves
        0. Click on "Bezier <--> B-spline"
        1. Click on a CONTROL POINT of a curve on screen
    Convert all curves to Bezier
        1. Click "All visible curve -> Bezier"
    Convert all curves to B-spline
        1. Click "All visible curve -> B-spline"

Operation on vertex
    These operations will apply on the closest curve that is not hidden
    If you want to specify a curve, use "Show only one curve", do the operation,
     then "Show all curves"
    Note that all B-spline curve information (order, knots) will be reset
    Add vertex at end
        1. Click "Add vertex at end"
        2. Click somewhere close to the END POINT of the curve
        3. If you want to add other vertices, no need to click button again
    Insert vertex at middle
        1. Click "Insert vertex at middle"
        2. Click somewhere close to the EDGE of the curve
        3. If you want to insert other vertices, no need to click button again
    Move vertex
        1. Click "Move vertex"
        2. Drag a vertex of the curve
        3. If you want to move other vertices, no need to click button again
    Delete vertex
        1. Click "Delete vertex"
        2. Click on vertex to delete
        3. When a curve has 0 vertices remaining, it will be deleted
        4. If you want to delete other vertices, no need to click button again

Other controls
    Specify resolution
        Use "Number of rendering points" scroll bar
        For B-spline curve, I implemented segment specific version of resolution

B-spline curve operations
    Controls for B-spline curves are on the right panel
    These operations will apply on selected B-spline curves (colored orange)
    Get info
        1. Click "Get info" button
        2. Click on a vertex of a B-spline curve
        3. Parameters of the B-spline curve will be loaded to the side window
        4. The B-spline curve will be selected (become orange)
    Adjust Order
        Use spinner "Order k" (input or adjust up / down)
    Adjust Knots
        Use scroll bar in "Knots" section to adjust knots.
        When computing, all Knot values will be sorted. So for example, if the
         input box is "u0=0, u1=2.5, u2=2", the program will treat it as
         "u0=0, u1=2, u2=2.5".
        If there are two values that are closer than 0.001, they will be assumed
         equal and the curve will not be drawn to prevent zero division error.

File I/O
    First specify a file name (default: "test_scene")
    Read file
        Press "Read file"
    Write file
        Press "Write file"
    Note that the current scene will only be saved after pressing "Write file"

Quit
    Press "Quit"