case 2: // Drawing Object 3
gluDisk(quadratic,0.5f,1.5f,32,32); // Draw A Disc (CD Shape)
break; // Done
Our fourth object is an object that I know many of you have been dying to figure out. The Sphere! This one is quite simple. The first parameter is the radius of the sphere. In case you're not familiar with radius/diameter, etc, the radius is the distance from the center of the object to the outside of the object. In this case our radius is 1.3f. Next we have our subdivision "around" the Z axis (32), and our subdivision "along" the Z axis (32). The more subdivisions you have the smoother the sphere will look. Spheres usually require quite a few subdivisions to make them look smooth.
case 3: // Drawing Object 4
gluSphere(quadratic,1.3f,32,32); // Draw A Sphere
break; // Done
Our fifth object is created using the same command that we used to create a Cylinder. If you remember, when we were creating the Cylinder the first two parameters controlled the radius of the cylinder at the bottom and the top. To make a cone it makes sense that all we'd have to do is make the radius at one end Zero. This will create a point at one end. So in the code below, we make the radius at the top of the cylinder equal zero. This creates our point, which also creates our cone.
case 4: // Drawing Object 5
glTranslatef(0.0f,0.0f,-1.5f); // Center The Cone
gluCylinder(quadratic, 1.0f, 0.0f, 3.0f, 32, 32); // A Cone With A Bottom Radius Of .5 And A Height Of 2
break; // Done
Our sixth object is created with gluPartialDisc. The object we create using this command will look exactly like the disc we created above, but with the command gluPartialDisk there are two new parameters. The fifth parameter (part1) is the start angle we want to start drawing the disc at. The sixth parameter is the sweep angle. The sweep angle is the distance we travel from the current angle. We'll increase the sweep angle, which causes the disc to be slowly drawn to the screen in a clockwise direction. Once our sweep hits 360 degrees we start to increase the start angle. the makes it appear as if the disc is being erased, then we start all over again!
case 5: // Drawing Object 6
part1+=p1; // Increase Start Angle
part2+=p2; // Increase Sweep Angle
if (part1>359) // 360 Degrees
{
p1=0; // Stop Increasing Start Angle
part1=0; // Set Start Angle To Zero
p2=1; // Start Increasing Sweep Angle
part2=0; // Start Sweep Angle At Zero
}
if (part2>359) // 360 Degrees
{
p1=1; // Start Increasing Start Angle
p2=0; // Stop Increasing Sweep Angle
}
gluPartialDisk(quadratic, 0.5f, 1.5f, 32, 32, part1, part2-part1); // A Disk Like The One Before
break; // Done
};
xrot+=xspeed; // Increase Rotation On X Axis
yrot+=yspeed; // Increase Rotation On Y Axis
return TRUE; // Keep Going
}
In the KillGLWindow() section of code, we need to delete the quadratic to free up system resources. We do this with the command gluDeleteQuadratic.
GLvoid KillGLWindow(GLvoid) // Properly Kill The Window
{
gluDeleteQuadric(quadratic); // Delete Quadratic – Free Resources
Now for the final part, they key input. Just add this where we check the rest of key input.
if (keys[' '] && !sp) // Is Spacebar Being Pressed?
{
sp=TRUE; // If So, Set sp To TRUE
object++; // Cycle Through The Objects
if (object>5) // Is object Greater Than 5?
object=0; // If So, Set To Zero
}
if (!keys[' ']) // Has The Spacebar Been Released?
{
sp=FALSE; // If So, Set sp To FALSE
}
Thats all! Now you can draw quadrics in OpenGL. Some really impressive things can be done with morphing and quadrics. The animated disc is an example of simple morphing.
Everyone if you have time go check out my website, TipTup.Com 2000.
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