CPS 1 - Spring - Jenkins 3/23

Java Graphics: Fractals and Animation

• Intro to Fractals
  • Definition
  • History
  • Why study them?
    • Image compression
    • Study of nature
    • Mathmatical properties
    • Art - they're fun to make and pleasing to the eye
  • Examples
    • Sierpinski gasket (lab 8)
    • Koch snowflake and curve
      • Koch curve applet
      • Koch curve code
    • Mandelbrot
  
  
• The Java you need to know to make your own fractals
  • Graphics coordinate system
    • (0, 0) is upper left corner
    • (width-1, height-1) is lower right corner
    • y coordinate is reverse from math coordinate plane - y decreases as you move up and increases as you move down
  • Canvas class - area used for drawing
    • Canvas drawingArea=new Canvas();
    • drawingArea.resize(width, height);
    • add(drawingArea);
  • Graphics class - used for drawing on Canvas
    • You can only get a Graphics instance after you have added the Canvas
    • Graphics brush=drawingArea.getGraphics();
    • brush.drawLine(x0, y0, x1, y1);
    • brush.clearRect(x0, y0, width, height);
  • Point class - used to story coordinates
    • Point start=new Point(x0, y0);
    • start.x is the integer x coordinate
    • start.y is the integer y coordinate
    • brush.drawLine(start.x, start.y, end.x, end.y);
  • Color class
    • Color c=new Color(percentRed, percentGreen, percentBlue);
    • Color c=Color.blue;
    • Available colors are: black, blue, cyan, darkGray, gray, green, lightGray, magenta, orange, pink, red, white, & yellow
    • Color c=Color.orange.brighter();
    • Color c=Color.red.darker();
    • brush.setColor(c);
  • Example code
  • Run the example applet
  
  
• Animation
  • Why study it? Because it's:
    • Useful for modeling/simulating
    • Good for creating special effects in films
    • Cool to show off animations on your web page
  • Naive algorithm for animation
    1. Draw figure
    2. Erase figure
    3. Alter figure's position
    4. Redraw figure in its new position
    5. Repeat above until done
    • Example code
    • Run example applet
  • Better algorithm
    1. Draw figure
    2. Alter figure's position
    3. Draw figure in new position
    4. Erase non-overlapping part of old figure
    5. Repeat above until done
    • Example (lab 9)
  • Ideal algorithm
    1. Draw image on screen
    2. Alter figure's position
    3. Draw new figure in an offscreen buffer
    4. Display new figure by putting the offscreen buffer on the screen
    5. Repeat above until done
    • Example with fractals
  
  
• The Java you need to know to make animations
  • Graphics ability from creating fractals
  • Graphics method copyArea(x0, y0, width, height, dx, dy)
    • (x0, yo) is the upper left corner of area to copy
    • width and height describe how much to copy
    • dx - amount to move right (or left if dx is negative)
    • dy - amount to move down (or up if dy is negative)
  • Must have "cushion" around area sufficient to erase non-overlapping part of previous draw
  • Must know how to use while loops to alter coordinates
  • Understand how machine speed affects animation speed
  • Example of a simple bouncing ball program
    • See the oode
    • Run the applet