A quick assignment for GLART, drawing an animated field of triangles.

White triangles on a black backgroundMore white triangles on a black backgroundEven more white triangles on a black backgroundYet more white triangles on a black background

Here’s the code:

package mika;
import java.awt.event.MouseEvent;
import javax.media.opengl.*;
import jocode.*;

/**
  * DemoBasicGeometry.java
  *
  * Demonstrate six types of geometry using glBegin()...glEnd()
  *
  * napier at potatoland dot org
  */

public class Week1 extends JOApp {

  // Set the mouse position in a way that's
  // useful for translating objects at 0 Z
  public float screenCursorX;
  public float screenCursorY;
  public float tempValue;
  public float sizeMult;

  /**
    * Start the application, Run() initializes the OpenGL context, calls setup(),
    * handles mouse and keyboard input, and calls draw() in a loop.
    */
  public static void main(String args[]) {
    // create the app
    Week1 demo = new Week1();

    // set title, window size
    windowTitle = "Hello World";
    displayWidth = 1440;
    displayHeight = 900;

    // start running: will call init(), setup(), draw(), mouse functions
    demo.run();
  }

  /**
    * Initialize settings. Will be called once when app starts. Called by
    * JOApp.init().
    */
  @Override
  public void setup() {
    // set a background color
    gl.glClearColor(0 f, 0 f, 0 f, 1 f);

    // Move over to my second monitor for testing...
    // TODO Disable this IRL
    frame.setLocation(-1440, 150);
  }

  /**
    * Render one frame. Called by the JOApp.display() callback function.
    */
  @Override
  public void draw() {

    // Clear screen and depth buffer
    gl.glClear(GL.GL_COLOR_BUFFER_BIT | GL.GL_DEPTH_BUFFER_BIT);

    // Select The Modelview Matrix (controls model orientation)
    gl.glMatrixMode(GL.GL_MODELVIEW);

    gl.glEnable(GL.GL_BLEND);
    gl.glBlendFunc(GL.GL_SRC0_ALPHA, GL.GL_ONE_MINUS_SRC_ALPHA);
    // gl.glBlendFunc(GL.GL_ONE, GL.GL_ONE);

    // Reset the Modelview matrix
    // this resets the coordinate system to center of screen
    gl.glLoadIdentity();

    // Where is the 'eye'
    glu.gluLookAt(0 f, 0 f, 10 f, // eye position
      6 f, 1 f, 0 f, // target to look at
      0 f, 1 f, 0 f); // which way is up

    // color will affect all the following verts
    gl.glColor4f(1 f, 1 f, 1 f, 0.5 f);
    // gl.glColor3f(1f, 1f, 1f);

    sizeMult = 3;
    tempValue = (tempValue + .02 f) % 1000;

    for (int i = 0; i < 200; i++) {
      gl.glRotatef(tempValue, tempValue, tempValue, tempValue);

      gl.glTranslatef(.1 f, .1 f, .1 f);

      gl.glBegin(GL.GL_TRIANGLES); {
        // top
        gl.glVertex3f(0 f, 0 f, 0 f);

        // lower left
        gl.glVertex3f(-0.5 f * sizeMult, -1 f * sizeMult, 0 f);

        // lower right
        gl.glVertex3f(0.5 f * sizeMult, -1 f * sizeMult, 0 f);
      }
      gl.glEnd();
    }

    // reset vertex color to white
    gl.glColor3f(1 f, 1 f, 1 f);
  }

  @Override
  public void mouseMoved(MouseEvent _event) {
    // Call the parent method since it actually gives us the
    // Better just to copy the whole method?
    super.mouseMoved(_event);
    screenCursorX = cursorX / (displayWidth / 10 f);
    screenCursorY = cursorY / (displayHeight / 10 f) - 3 f;
  }

}