CS 457/557 -- Winter Quarter 2023

Project #1

Step- and Blended-edged Elliptical Dots

60 Points

Due: January 20

This page was last updated: January 8, 2023


  1. Use GLSL and either glman or the GLSL API to render some geometry (your choice), covered with elliptical dots.

  2. Remember that the border of an ellipse, defined in s and t coordinates is:
    (s-sc)2 / Ar2 + (t-tc)2 / Br2 = 1
    Be sure you compute the ellipse centers, sc and tc, correctly.

  3. The ellipse parameters must be set as uniform variables from glman sliders, like this:
    ##OpenGL GLIB
    Perspective 90
    LookAt 0 0 2  0 0 0  0 1 0
    Vertex   oval.vert
    Fragment oval.frag
    Program  Oval				\
    	uAd <.001 .1 .5>		\
    	uBd <.001 .1 .5>		\
    	uTol <0. 0. 1.>
    Color 1. .9 0
    Sphere 1 50 50

    This will produce sliders for

    ParameterWhat It Does
    uAdEllipse diameter for s
    uBdEllipse diameter for t
    uTolWidth of the blend between ellipse and non-ellipse areas

  4. Apply lighting. You can do this simply in the vertex shader, like this:
    #version 330 compatibility
    out vec3  vMCposition;
    out float vLightIntensity; 
    const vec3 LIGHTPOS   = vec3( -2., 0., 10. );
    main( )
    	vST = gl_MultiTexCoord0.st;
    	vec3 tnorm      = normalize( gl_NormalMatrix * gl_Normal );
    	vec3 ECposition = vec3( gl_ModelViewMatrix * gl_Vertex );
    	vLightIntensity  = abs( dot( normalize(LIGHTPOS - ECposition), tnorm ) );
    	vMCposition  = gl_Vertex.xyz;
    	gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;
    or, you can do the full per-fragment-lighting thing.

  5. The uTol parameter is the width of a smoothstep( ) blend between the ellipse and non-ellipse areas, thus smoothing the abrupt color transition.
    float t = smoothstep( 1. - uTol, 1. + uTol, results_of_ellipse_equation );
    Then use t in the mix function.

  6. The choice of geometry is up to you. Keep it simple at first, then, if there is still time, feel free to get more creative. To try out the bunny010n.obj model, use the GLIB line:
    Obj bunny010n.obj
    where the bunny010n.obj file needs to be in the same folder as your .cpp, .glib, .vert, and .frag files.


The Turn-In Process:

Your turnin will be done at http://teach.engr.oregonstate.edu and will consist of:

  1. All source files (.cpp, .glib, .vert, .frag). You can zip this all together if you want.
  2. A PDF report with a title, your name, your email address, nice screen shots from your program, and the link to the Kaltura video or YouTube video demonstrating that your project does what the requirements ask for. Narrate your video so that you can tell us what it is doing.
  3. Be sure your video's protection is set to unlisted.
  4. Do not put your PDF into your zip file. Leave it out separately so my collect-all-the-PDFs script can find it.

Submissions are due at 23:59:59 on the listed due date.


Hard-edged elliptical dots10
Smooth-edged elliptical dots with varying uTol20
Correct elongation when varying uA and uB30
Potential Total60