Applying Textures and Simple Animations to Our Scene - WebGL Game Development - page 224

this.rotations.push((j*22/7)/180);
}
this.visible=false;
this.counter=0;
this.grenadeCallback=null;
});
In the update function, we obtain the camera view matrix. Calculate the camera
matrix, then translate the arm with respect to the camera using the matrix. Then,
apply a rotation transformation along the x axis with an angle from the rotations
array. Note that in the case of the left arm, we use the latest value of the camera view
matrix throughout the animation. This is done so that during the animation if you
rotate or translate your camera, the arm moves with it. Also, when we have iterated
over the complete set of rotations, it resets the counter , toggles visibility, and invokes
the callback function.
LeftHand.prototype.update=function() {
if(this.counter<this.rotations.length) {
var mMatrix=mat4.clone(this.camera.viewMatrix);
mat4.invert(mMatrix,mMatrix);
mat4.translate(this.modelMatrix,mMatrix,vec3.fromValues(-1.5,-3,-6));
mat4.rotateX(this.modelMatrix,this.modelMatrix,this.rotations[this.
counter]);
this.counter=this.counter+1;
}else{
this.counter=0;
this.visible=false;
this.grenadeCallback();
}
}
Open the grenade.js file from the primitive/game folder in your editor.
The Grenade class is very similar to the Bullet class except for one difference: we
do not calculate the interpolates in the initialize function. We calculate it over the
control points once the application is loaded in the main control code. Each time the
animation is required to run, we pass the positions array from the main code as a
parameter to the initialize function.
Grenade= inherit(StageObject, function (){
superc(this);
this.positions=[];
this.counter=0;
this.visible=false;
this.initialModelMatrix=mat4.create();
});