3D Game Programming

functionmakeTreeAt(x, z) {

vartrunk =newTHREE.Mesh(

newTHREE.CylinderGeometry(50, 50, 200),

newTHREE.MeshBasicMaterial({color: 0xA0522D})

);

vartop =newTHREE.Mesh(

newTHREE.SphereGeometry(150),

newTHREE.MeshBasicMaterial({color: 0x228B22})

);

top.position.y = 175;

trunk.add(top);

trunk.position.set(x, -75, z);

scene.add(trunk);

}

If you entered all that code correctly, you’ll see the avatar standing in front

of a forest of four trees.

That’s pretty cool, but how did we do that?

Breaking It Down

The first part of the forest-building is pretty easy to follow. We add trees at

different X and Z coordinates (remember that Y is up and down) around the

scene.

makeTreeAt( 500, 0);

makeTreeAt(-500, 0);

makeTreeAt( 750, -1000);

makeTreeAt(-750, -1000);

That’s easy enough, but how does that makeTreeAt() thing work?

As we’ll see in Chapter 5, Functions: Use and Use Again, on page 49, a Java-

Script function is a way to run the same code over and over. In this case, we

report erratum • discuss

Building a Forest with Functions • 41

Prepared exclusively for Michael Powell