3D Game Programming

Now comes the interesting work that Levels does. It needs to be able to level

up when the player clears a level. As long as there are more levels, leveling

up should erase the current level, increase the current level number, then

draw the next level. Last, we need to tell the countdown timer to reset, but

with a bit less time.

Levels.prototype.levelUp =function() {

if(!this.hasMoreLevels())return;

this.erase();

this.current_level++;

this.draw();

this.scoreboard.resetCountdown(50 - this.current_level * 5);

};

That’s a nice little method that does exactly what we want it to do. It is tricky

to write code that reads like simple instructions (and sometimes it’s not pos-

sible). But code like that this is something to strive for.

We’re not quite done with the Levels object. The first thing the levelUp() method

does is ask if it has more levels. We need to add that method as follows:

Levels.prototype.hasMoreLevels =function() {

varlast_level = this.levels.length-1;

returnthis.current_level < last_level;

};

If there are two levels in the game, then hasMoreLevels() should be true when

we’re on the first level and false when we’re on the second level. Since Java-

Script likes to start counting from zero, this.current_level will be zero on the first

level and one on the second level. In other words, the last level in a two-level

game would be when this.current_level is one.

Counting from Zero Can Be Difficult

Doing math when you start counting at zero instead of one can be

confusing. It usually helps to plug in real numbers—especially

numbers just before and after the end of a list.

That does it for defining our Levels object. Before we try using it, add the fol-

lowing buildObstacle() method:

functionbuildObstacle(shape_name, x, y) {

varshape;

if(shape_name =='platform') {

shape =newTHREE.CubeGeometry(height/2, height/10, 10);

}else{

shape =newTHREE.CylinderGeometry(50, 2, height);

}

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Building Levels • 181

Prepared exclusively for Michael Powell