HTML5画布游戏将子弹射击到鼠标指向。

Question

Right now. I have it setup to shoot bullets from the direction of my character. But I want to be able to shoot bullets to the mouse point, making it easier on the player.

Right now it's

if(gun_1[i].direction == 2){ gun_1[i].x -= gun_1[i].speed * modifier};
if(gun_1[i].direction == 3){ gun_1[i].x += gun_1[i].speed * modifier};
if(gun_1[i].direction == 1){ gun_1[i].y -= gun_1[i].speed * modifier};
if(gun_1[i].direction == 4){ gun_1[i].y += gun_1[i].speed * modifier };
if(gun_1[i].direction == 5){ gun_1[i].y -= gun_1[i].speed * modifier; gun_1[i].x -= gun_1[i].speed * modifier };
if(gun_1[i].direction == 7){ gun_1[i].y += gun_1[i].speed * modifier; gun_1[i].x -= gun_1[i].speed * modifier };
if(gun_1[i].direction == 6){ gun_1[i].y -= gun_1[i].speed * modifier; gun_1[i].x += gun_1[i].speed * modifier };
if(gun_1[i].direction == 8){ gun_1[i].y += gun_1[i].speed * modifier; gun_1[i].x += gun_1[i].speed * modifier };

I want to be able to shoot to location of where the mouse was clicked. If it is possible.

Answer 1

Sure, that's not too hard. But there is also a lot you can do to improve your current design. First of all, add velocityX and velocityY fields so that on each step you just need to update the bullets' positions:

gun_1[i].x += gun_1[i].velocityX
gun_1[i].y += gun_1[i].velocityY

Then when the mouse is pressed, set the bullets' velocities:

canvas.onmousedown = function(e) {
   var dx = (e.x - character.x);
   var dy = (e.y - character.y);
   var mag = Math.sqrt(dx * dx + dy * dy);

   // whatever you need to do to get gun_1[i]

   gun_1[i].velocityX = (dx / mag) * speed;
   gun_1[i].velocityY = (dy / mag) * speed;
}

If you know a thing or two about vectors we're just normalizing the direction vector and multiplying with the scalar initial speed.

Answer 2

Another answer:

gun_1[i].x += gun_1[i].velocityX;
gun_1[i].y += gun_1[i].velocityY;


var dx = (e.x - character.x);
var dy = (e.y - character.y);
var angle = Math.atan2(dy, dx);

gun_1[i].velocityX = Math.cos(angle) * speed;
gun_1[i].velocityY = Math.sin(angle) * speed;

Answer 3

   var i=0;
        var maxBullets=10;
        var allBullets=[];//a array for objects

        function bullet(){
           this.vx=0;
           this.vy=0;
           this.inix=0;
           this.iniy=0;
           this.angleGrads=0;
           this.angleRads=1.0;
           this.active=false;
        }
        bullet.prototype.exist=function(){
         //this.inix+=mathsin.bla,bla.bla.bla  bla
         if(this.x > wordWidth){
           //kill this bullet
           this.active=false;
          }
        }
        bullet.prototype.draw=function(){
          //ctx.draw bla, bla, bla 
        }
        function newBullets(){
          for(i=1;i<=maxBullets;i++){
            allBullets[i]=new bullet();
          }
        }
    function launchBullets(){
         for(i=1;i<=maxBullets;i++){
            if(!allBullets[i].active){
              //detemine angle with a point an the mouse point
              // math atan2()  ;)
              //asing values to this bullet
             allBullets[i].angleGrads=angleMouse;
             allBullets[i].inix=mousex;
             allBullets[i].iniy=mousey;
             allBullets[i].angleRads=(allBullets[i].angleGrads*PI)/180;
             //and end
             allBullets[i].active=true;
             //get out
             break;
            }
          }
    }//end of launchBullets

    function operations(){
      for(i=1;i<=maxBullets;i++){
            if(allBullets[i].active){
              allBullets[i].exist();
        }
      }
    }
    function paint(){
    for(i=1;i<=maxBullets;i++){
            if(allBullets[i].active){
              allBullets[i].draw();
        }
      }
    }//end of draw scene