/*
* Sends a quadrilateral to the OpenGL pipeline. Mimics the other quad
* function.
*/
public static void quad(
Vector3f v0, Vector3f v1, Vector3f v2, Vector3f v3, Vector3f n, Color3f c, GLAutoDrawable d) {
GL2 gl = d.getGL().getGL2();
gl.glBegin(GL2.GL_QUADS);
gl.glColor3f(c.x, c.y, c.z);
gl.glNormal3f(n.x, n.y, n.z);
gl.glTexCoord2f(t0.x, t0.y);
gl.glVertex3f(v0.x, v0.y, v0.z);
gl.glTexCoord2f(t1.x, t1.y);
gl.glVertex3f(v1.x, v1.y, v1.z);
gl.glTexCoord2f(t2.x, t2.y);
gl.glVertex3f(v2.x, v2.y, v2.z);
gl.glTexCoord2f(t3.x, t3.y);
gl.glVertex3f(v3.x, v3.y, v3.z);
gl.glEnd();
}
/** Called back by the animator to perform rendering. */
@Override
public void display(GLAutoDrawable drawable) {
GL2 gl = drawable.getGL().getGL2(); // get the OpenGL 2 graphics context
gl.glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // clear color and depth buffers
for (int i = 0; i < stars.length; i++) {
// Reset the view (x, y, z axes back to normal)
gl.glLoadIdentity();
gl.glTranslatef(0.0f, 0.0f, z);
// The stars are texture quad square drawn on x-y plane and
// distributed on on x-z plane around the y-axis
// Initial 90 degree tile in the x-axis, y-axis pointing out of screen
gl.glRotatef(tilt, 1.0f, 0.0f, 0.0f);
// Rotate about y-axis (pointing out of screen), initial angle is 0
gl.glRotatef(stars[i].angle, 0.0f, 1.0f, 0.0f);
// Translate about the x-axis (pointing right) to its current distance
gl.glTranslatef(stars[i].distance, 0.0f, 0.0f);
// The stars have initial angle of 0, and initial distance linearly
// distributed between 0 and 5.0f
// Rotate the axes back, so that z-axis is again facing us, to ensure that
// the quad (with texture) on x-y plane is facing us
gl.glRotatef(-stars[i].angle, 0.0f, 1.0f, 0.0f);
gl.glRotatef(-tilt, 1.0f, 0.0f, 0.0f);
// Take note that without the two rotations and undo, there is only one
// translation along the x-axis
// Matrix operation is non-commutative. That is, AB != BA.
// Hence, ABCB'A' != C
// Draw the star, which spins on the z axis (pointing out of the screen)
gl.glRotatef(starSpinAngle, 0.0f, 0.0f, 1.0f);
// Set the star's color using bytes (why bytes? not float or int?)
gl.glColor4ub(stars[i].r, stars[i].g, stars[i].b, (byte) 255);
gl.glBegin(GL_QUADS);
// draw a square on x-y plane
gl.glTexCoord2f(textureCoordLeft, textureCoordBottom);
gl.glVertex3f(-1.0f, -1.0f, 0.0f);
gl.glTexCoord2f(textureCoordRight, textureCoordBottom);
gl.glVertex3f(1.0f, -1.0f, 0.0f);
gl.glTexCoord2f(textureCoordRight, textureCoordTop);
gl.glVertex3f(1.0f, 1.0f, 0.0f);
gl.glTexCoord2f(textureCoordLeft, textureCoordTop);
gl.glVertex3f(-1.0f, 1.0f, 0.0f);
gl.glEnd();
// If twinkling, overlay with another drawing of an arbitrary color
if (twinkleOn) {
// Assign a color using bytes
gl.glColor4ub(
stars[(numStars - i) - 1].r,
stars[(numStars - i) - 1].g,
stars[(numStars - i) - 1].b,
(byte) 255);
gl.glBegin(GL_QUADS);
// draw a square on x-y plane
gl.glTexCoord2f(textureCoordLeft, textureCoordBottom);
gl.glVertex3f(-1.0f, -1.0f, 0.0f);
gl.glTexCoord2f(textureCoordRight, textureCoordBottom);
gl.glVertex3f(1.0f, -1.0f, 0.0f);
gl.glTexCoord2f(textureCoordRight, textureCoordTop);
gl.glVertex3f(1.0f, 1.0f, 0.0f);
gl.glTexCoord2f(textureCoordLeft, textureCoordTop);
gl.glVertex3f(-1.0f, 1.0f, 0.0f);
gl.glEnd();
}
// Update for the next refresh
// The star spins about the z-axis (pointing out of the screen), and spiral
// inwards and collapse towards the center, by increasing the angle on x-y
// plane and reducing the distance.
starSpinAngle += 0.01f; // used to spin the stars about the z-axis
// spiral pattern
stars[i].angle += (float) i / numStars; // changes the angle of a star
// collapsing the star to the center
stars[i].distance -= 0.01f; // changes the distance of a star
// re-bone at the edge
if (stars[i].distance < 0.0f) { // Is the star collapsed to the center?
stars[i].distance += 5.0f; // move to the outer ring
stars[i].setRandomRGB(); // choose a random color for the star
}
}
}
/*
* Recursively generates a sphere using triangles and puts the resulting
* polygons into the OpenGL pipeline. Mimics the other spheretri function.
*/
private static void spheretri(
int n, Vector3f v0, Vector3f v1, Vector3f v2, Color3f c, GLAutoDrawable d) {
GL2 gl = d.getGL().getGL2();
if (n == 0) {
if (pipe.isFlatShaded()) {
nrml.add(v0, v1);
nrml.add(v2);
nrml.normalize();
gl.glBegin(GL.GL_TRIANGLES);
gl.glColor3f(c.x, c.y, c.z);
gl.glNormal3f(nrml.x, nrml.y, nrml.z);
gl.glVertex3f(v0.x, v0.y, v0.z);
gl.glVertex3f(v1.x, v1.y, v1.z);
gl.glVertex3f(v2.x, v2.y, v2.z);
gl.glEnd();
} else {
gl.glBegin(GL.GL_TRIANGLES);
gl.glColor3f(c.x, c.y, c.z);
xyTex(v0, texs[0]);
xyTex(v1, texs[1]);
xyTex(v2, texs[2]);
gl.glNormal3f(v0.x, v0.y, v0.z);
gl.glTexCoord2f(texs[0].x, texs[0].y);
gl.glVertex3f(v0.x, v0.y, v0.z);
gl.glNormal3f(v1.x, v1.y, v1.z);
gl.glTexCoord2f(texs[1].x, texs[1].y);
gl.glVertex3f(v1.x, v1.y, v1.z);
gl.glNormal3f(v2.x, v2.y, v2.z);
gl.glTexCoord2f(texs[2].x, texs[2].y);
gl.glVertex3f(v2.x, v2.y, v2.z);
gl.glEnd();
}
} else {
Vector3f v01 = new Vector3f();
Vector3f v12 = new Vector3f();
Vector3f v20 = new Vector3f();
v01.add(v0, v1);
v01.normalize();
v12.add(v1, v2);
v12.normalize();
v20.add(v2, v0);
v20.normalize();
spheretri(n - 1, v01, v12, v20, c, d);
spheretri(n - 1, v0, v01, v20, c, d);
spheretri(n - 1, v1, v12, v01, c, d);
spheretri(n - 1, v2, v20, v12, c, d);
}
}