Computer Graphics
Homework 01
6 hours
 
Copyright © 2000 David C. Banks

1. 0.25 hours
   Box filter

2. 0.50 hours
   Tent filter

3. 0.50 hours
   Quadratic filter

4. 0.75 hours
   Cubic filter

5. 1.25 hours
   Quartic filter

6. 2.00 hours
   Create an image class. An image contains xDim*yDim pixels and contains a function filter() and a radius (measured in pixels). It also supports a method setPixel().
   To set a pixel's color, use the filter function as a weight for the pixel's neighborhood of the desired radius. Use/modify the code below to draw a fat dot at location (x,y).

   void
   Image::setPixel(double _x, double _y, double _z,
   		double _r, double _g, double _b)
     {
     int xiMin, xiMax, yiMin, yiMax; // integer valued locations
     double xCenter, yCenter;        // (_x, _y) in array coords
     double distance;                // distance between points
   
     xCenter = (_x - xMin)*(xDim - 1.0)/(xMax - xMin);
     yCenter = (_y - yMin)*(yDim - 1.0)/(yMax - yMin);
   
     xiMin = ceil (xCenter - radius);
     xiMax = floor(xCenter + radius);
     yiMin = ceil (yCenter - radius);
     yiMax = floor(yCenter + radius);
   
     // Clamp xiMin to the interval [0, xDim-1], etc.
     //
     // You implement the clamp() routine.
   
     clamp(xiMin, 0, xDim-1);        
     clamp(xiMax, 0, xDim-1);
     clamp(yiMin, 0, yDim-1);
     clamp(yiMax, 0, yDim-1);
   
     double w;                       // weight from filter
     int index;                      // array index
     for (int yi = yiMin; yi <= yiMax; yi++)
       {
       for (int xi = xiMin; xi <= xiMax; xi++)
         {
         distance = sqrt((xCenter-xi)*(xCenter-xi) + 
   		      (yCenter-yi)*(yCenter-yi) );
         w        = filter(distance);
   
         index    = yi*xDim + xi;
   
         pixel[index].x      += w*_x;
         pixel[index].y      += w*_y;
         pixel[index].z      += w*_z;
         pixel[index].red    += w*_r;
         pixel[index].green  += w*_g;
         pixel[index].blue   += w*_b;
         pixel[index].weight += w;
         }
       }
     }
   

7. 0.50 hours
   Use your Image class to create a .ppm file that is 300x200 pixels. Choose xMin = -1, xMax = 1, yMin = -1, yMax = 1. Choose radius = 27 pixels. Use the non-normalized tent filter. Draw
   a pale green dot in the upper right part of the image
   a gray dot in the upper left part of the image
   a brown dot in the lower left part of the image
   a red dot in the lower right part of the image
   a green dot in the middle of the image
   a blue dot slightly offscreen.
   Convert the image to gif. Insert into your Web page.
   Link your code, headers, and Makefile from your Web page.
   Create a tar.gz file for the directory for this assignment.

8. 0.25 hours
   Print two copies of the homework 01 grade sheet.
   Print this page.
   Print your code, headers, and Makefile.
   Print your Web page for this assignment.
   Put them inside your notebook to turn in.

9. Extra credit (100 points)
   Write a program to draw a bunch of dots with different colors, different radii, different centers, different filters. Convert the ppm file to gif. Put it on your Web page, print it for your notebook, include the source code.

10. Extra credit (100 points)
    Make your program read the center, radius, color, filter for each dot from the command line. Drive it with a script so that the dot move. Make a gif animation. Put it on your Web page.