Danmaku using Phaser 3 (step 12): Random Rolling N-Way

What if we gave the bullets a bit of "randomness"? In this post I look at how I added randomness to the fire interval of bullets and their direction to the Rolling n-Way danmaku I created in the previous post.

Adding randomness to the bullet fire interval

The consecutive firing of bullets is controlled by a Phaser timer event, created under the name of this.machineGun within the constructor function of the DanmakuWrapper. The delay between each bullet is set by 'delay: this.timeBetweenBullets'. All we need to do is change this delay property of the timer event, every time we fire the bullet. We can do this in the fireweapon function of the danmaku object. We will also create a new property for the danmaku object called 'randomBulletDelay' which will act as a boolean flag to tell whether we should randomise or not. We simply add the following line at the beginning of the fireweapon method.

if (this.randomBulletDelay) {
      this.machineGun.delay = this.timeBetweenBullets + Phaser.Math.Between(-this.timeBetweenBullets,this.timeBetweenBullets);
    } // to randomise the fire interval of bullets or not

This will add a random number between minus this.timeBetweenBullets and positive this.timeBetweenBullets to the prescribed fire bullet interval, and set the delay timer to the new time.

Adding randomness to the bullet direction

We will create another new property for the danmaku object called 'randomBulletAngle' which will tell if and how the bullet direction should be randomised.

We will use the following function to calculate the "randomness" in bullet direction

randomiseDirection() { // function to return a "random element" to add to the bullet angle
    if (this.randomBulletAngle.status) {
      return Phaser.Math.Between(-this.randomBulletAngle.range /2, this.randomBulletAngle.range /2)
    } 
    else
      return 0;
  } // end of randomiseDirection function

Then all we have to do is add what's returned from the above function to bits of our original code that calculates the bullet angle. The bold highlighted bits are the additions.

// calculate the direction of each cannon and store in an array
    const cannonAngles = [];
    if (this.numberOfCannons <= 1) { // single cannon 
      cannonAngles[0] = this.angle + this.randomiseDirection(); 
    } // end of calculating angle for where there is only 1 cannon
    else {
      if (this.cannonAngleRange < 360) { // there is more than 1 cannon and angle < 360
        for (let i = 0; i < this.numberOfCannons; i++) {    
          cannonAngles[i] = this.angle + (i  / (this.numberOfCannons-1) - 0.5) * this.cannonAngleRange + this.randomiseDirection();  
        } // end of for loop where cannon range is less than 360
      } // end of if statement checking cannons > 1 && cannonAngle Range < 360    
      else { // get here if there's more than 1 cannon, and Cannon angle range is 360           
        for (let i = 0; i < this.numberOfCannons; i++) {
          cannonAngles[i] = this.angle + (360 / this.numberOfCannons) * i + this.randomiseDirection();
        } // end of for loop where cannon range = 360
      }
    }

And that's it! The entire code is available in the following CodePen for your perusal.