CS 258 Spring 2011

Introduction to Computer Graphics

This code is primarily for archival/demonstration purposes. This is the coursework for CS 258 - Introduction to Computer graphics, which consisted of five programs that built on each other - all with fairly low-level C/C++ implementation.

While the organization, testing, and documentation are much more rudimentary than my current work, it demonstrates more technical work than more current app/website work.

• Project 1: Command line interpreter
• Project 2: TIFF read/write
• Project 3: Image Resizing
• Project 4: 3D Transformations
• Project 5: Ray Tracing

Updated July 2021 to make sure still runs (using Manjaro linux).

Orgininal (as-submitted) code on branch as_submitted

Build system switched entirely to CMake

Building

• Requires OpenGL, GLUT, and X11 libraries (installed so CMake can find)
• Run on Manjaro 21.1.0, didn't verify which packages provided the libraries

1. Run Cmake (ex: from project root cmake -S . -B build)
2. Switch to build folder (cd build)
3. Compile (make)
4. Execute binary (ipr)

Notes on running

• Keep in mind need to make sure the graphics window needs to be selected for keyboard input, not the terminal it was launched from.
• Scripts in the scripts folder should be run from one level up.
• Several scripts like test.icf are intended to have an error.

Supported commands:

Most of this documentation is from well after the period the class. This was for a class, with no requirements on documentation, to a spec. (And we hadn't even covered Doxygen-style documentation.) There may be some errors, see the scripts and/or the specifications if more information is needed. Furthermore, some parts of the assignments focus on fairly technical implementations. The assignment specification at times assumes technical knowledge and is not user-friendly. Especially the raytracer and 3D portions are not for the casual user.

Basic commands

• read <file> - reads contents of file treating each line as a command
• pause - waits for keypress (with graphical window selected) to continue
• reset - sets the image array to black
• resizewin <w> [<h>] - resizes window to provided dimensions.
  • If omitted, h is copied from w
• exit - exit the program

TIFF commands

As a convenience, will try to get image in ./images directory before failing.

• tiffstat <file> - Display info about TIFF file
• tiffread <file> - Read file to window
• tiffwrite <file>- Write window to file
• iotest <file> - test read function with some TIFF values filled in

Image resize commands

• resize <factor> - Resizes by specified factor.
  • Negative values will flip the image
• resize <x_factor> <y_factor> Resize by different factors on x and y axis
• scale <factor> - Resizes by specified factor
• border <type> - Changes how the image edge is handled for multipixel resize filters
  • zero - (default) outside pixels are black
  • freeze- pixel matches closest edge pixel
  • circular - reflects pixels that cross the edge
  • truncate - re-weight the filter to ignore outside pixels
• select <method> [<filter_width>] - sets the resize method
  • Methods include lanczos, gaussian, mitchell, hamming, hann, tent, triangle, box
  • Parameter filter_width defaults to 0

3D Image Commands

The 3D drawing is performed by maintaining a stack of matrix transformations (initialized with the identity matrix). All lines drawn are treated as a vector and multiplied against the top of the transform stack before being drawn.

• push - Adds duplicate of topmost item to transformation stack
• pop - Manipulates the transform matrix stack
• translate x y z - Translate by elementary translation matrix created from (x y z)
• scale sx sy sz - Scale with scaling matrix created from (sx sy sz)
• rotate <angle> ax ay az - Rotate around axis (ax, ay, az) by angle in degrees
• ortho l r b t n f - Implement orthographic projection on the vertices
  • This is assumed viewing along the negative z-axis, displaying from n (near) to f (far).
  • The x-axis bounds are from l (left) to r (right)
  • The y-axis bounds are from t (top) to b (bottom)
• orient <a...i> - Used to create an arbitrary transformation matrix

   | a  b  c  0 |
   | d  e  f  0 |
   | g  h  i  0 |
   | 0  0  0  1 |

• perspective fov a n f - Implement perspective transformation
  • This is assumed from the origin along the negative z-axis
  • View is described in field of view fov and aspect ratio a
  • View clipped from n (near) to f (far) along the negative z-axis
• lookat fx fy fz ax ay az ux uy uz - Change point of view
  • Camera location specified by (fx, fy, fz)
  • Direction (at) vector specified by (ax, ay, az)
  • Up vector specified by (ux uy uz)
• vertex <x> <y> <z> - Draw line between points
• printc - Debug command to show the top of the transformation stack
• printview - Debug command to show information about the view (from perspective or ortho)
• debug3d - Toggle debug (verbose) mode

3D Raytracing Commands

The raytracing part functions by

1. Set up the screen
2. Set up the camera
3. Add object(s)
4. Add light(s)
5. Run trace to render the scene

Colors for the various commands in this module are floats ranging from (0.0, 0.0, 0.0) as black to (1.0, 1.0, 1.0) as white.

The various commands are

• screen - Set screen resolution
• orthocamera - Setup camera as orthogonal using the screen width and height
• camera w h Ex Ey Ez Gx Gy Gz Ux Uy Uz dist au av bu bv Setup perspective camera
  • Screen dimenstions w by h
  • The eye vector (Ex Ey Ez) - where the eye is located
  • The gaze vector (Gx Gy Gz) - where the eye is looking
  • The up vector (Ux Uy Uz) - which direction is up from the eye
  • The screen is from (au av dist) to (bu bv dist)
• background r g b - Sets the background color, shown when the pixel's ray doesn't hit anything. Arguments default to 0.0
• sphere x y z r Mr Mg Mb Rr Rg Rb [Sr Sg Sb] - Create a sphere in the scene
  • The sphere is centered on (x y z) with radius r
  • (Mr, Mg, Mb) specifies the ambient color (RGB)
  • (Rr, Rg, Rb) specifies the reflective color (RGB)
  • (Optional) (Sr, Sg, Sb) specifies the specular color (RGB)
• triangle Ax Ay Az Bx By Bz Cx Cy Cz Mr Mg Mb Rr Rg Rb [Sr Sg Sb]
  • The three vertices are (Ax, Ay, Az), (Bx, By, Bz), (Cx, Cy, Cz)
  • (Mr, Mg, Mb) specifies the ambient color (RGB)
  • (Rr, Rg, Rb) specifies the reflective color (RGB)
  • (Optional) (Sr, Sg, Sb) specifies the specular color (RGB)
  • The triangles are visible from either side
• box Ax Ay Az Bx By Bz Mr Mg Mb Rr Rg Rb [Sr Sg Sb]
  • The box is specified by the two points (Ax, Ay, Az) and (Bx By Bz). The points are opposite corners, with edges along the axis.
  • (Mr, Mg, Mb) specifies the ambient color (RGB)
  • (Rr, Rg, Rb) specifies the reflective color (RGB)
  • (Optional) (Sr, Sg, Sb) specifies the specular color (RGB)
• ilight r g b x y z - Creates a light at infinity with color (r, g, b) shining in direction (x, y, z)
• clear - resets all objects, lights, and the viewscreen. Additionally the background color is set to black (0, 0, 0)
• trace - Runs the raytracer on configured objects and puts to the screen

Dummy commands

for purposes of having a CLI, will just print out the provided arguments

Default values provided for move and draw of (0, 0, 0)

• move x y z
• draw x y z
• color r g b

Additional notes

Project submission notes included in ProjectNotes#.txt for respective project

Assignment specifications included in specs folder. (Project 5 not available)