Beispiel für HTML5-Tischtennis (Kollisionserkennung), zwei_HTML5-Tutorialfähigkeiten

<script> <br>var ctx; <br>Var-Leinwand; <br>var ball_x=10; <br>var ball_y=10; <br>var ball_radius=10; <br>var ball_vx=10; <br>var ball_vy=8; <br>var wall_x=30; <br>var wall_y=40; <br>var wall_width=30; <br>var wall_height=60; <br>var box_x=0; <br>var box_y=0; <br>var box_width=300; <br>var box_height=300; <br>varbound_left=box_x ball_radius; <br>varbound_right=box_x box_width-ball_radius; <br>varbound_top=box_y ball_radius; <br>varbound_bottom=box_y box_height-ball_radius; <br>var-Einheit=10; <br>Funktion intersect(sx, sy, fx, fy, cx, cy, rad) <br>{ <br>var dx; <br>var dy; <br>var t; <br>var rt; <br>dx = fx - sx; <br>dy = fy – sy; <br>t = 0,0 - (((sx - cx) * dx (sy - cy) * dy) / (dx * dx dy * dy)); <br>if (t < 0.0) <br />{ <br />t = 0.0; <br />} <br />else if (t > 1.0) <br>t = 1.0; <br>var dx1 = (sx t * dx) - cx; <br>var dy1 = (sy t * dy) - cy; <br>var rt = dx1 * dx1 dy1 * dy1; <br>if (rt < rad * rad) <br />true zurückgeben; <br />else <br />return false; <br />} <br />function move_ball() <br />{ <br />ball_x=ball_x ball_vx; <br />ball_y=ball_y ball_vy; <br />if(ball_x<bound_left) <br />{ <br />ball_x=bound_left; <br />ball_vx=-ball_vx; <br />} <br />if(ball_x>bound_right) <br>{ <br>ball_x=bound_right; <br>ball_vx=-ball_vx; <br>} <br>if(ball_y<bound_top) <br />{ <br />ball_y=bound_top; <br />ball_vy=-ball_vy; <br />} <br />if(ball_y>bound_bottom) <br>{ <br>ball_y=bound_bottom; <br>ball_vy=-ball_vy; <br>} <br>//撞到上边 <br>if(intersect(wall_x,wall_y,wall_x wall_width,wall_y wall_height,ball_x,ball_y,ball_radius)) <br>{ <br>ball_y=wall_y-ball_radius; <br>ball_vy=-ball_vy; <br>} <br>//撞到左边 <br>if(intersect(wall_x,wall_y,wall_x,wall_y wall_height,ball_x,ball_y,ball_radius)) <br>{ <br>ball_x=wall_x-ball_radius; <br>ball_vx=-ball_vx; <br>} <br>//撞到右边 <br>if(intersect(wall_x wall_width,wall_y,wall_x wall_width,wall_y wall_height,ball_x,ball_y,ball_radius)) <br>{ <br>ball_x=wall_x wall_width ball_radius; <br>ball_vx=-ball_vx; <br>} <br>//撞到下边 <br>if(intersect(wall_x,wall_y wall_height,wall_x wall_width,wall_y wall_height,ball_x,ball_y,ball_radius)) <br>{ <br>ball_y=wall_y wall_height ball_radius; <br>ball_vy=-ball_vy; <br>} <br>} <br>function move_wall(ev) <br>{ <br>var keyCode; <br>if(event==null) <br>{ <br>keyCode=window.event.keyCode; <br>window.event.preventDefault(); <br>} <br>else <br>{ <br>keyCode=event.keyCode; <br>event.preventDefault(); <br>} <br>switch(keyCode) <br>{ <br>case 37://left; <br>wall_x-=unit; <br>if(wall_x<bound_left) <br />wall_x=bound_left; <br />Pause; <br />case 38://up <br />wall_y-=unit; <br />if(wall_y<bound_top) <br />wall_y=bound_top; <br />Pause; <br />case 39://right <br />wall_x =unit; <br />if(wall_x wall_width>bound_right) <br>wall_x=bound_right-wall_width; <br>Pause; <br>case 40://down <br>wall_y =unit; <br>if(wall_y wall_height>bound_bottom) <br>wall_y=bound_bottom-wall_height; <br>Pause; <br>Standard: <br>Pause; <br>} <br>} <br>function draw_all() <br>{ <br>ctx.beginPath(); <br>ctx.clearRect(box_x,box_y,box_width,box_height); <br>ctx.fillStyle="rgb(255,0,0)"; <br>//ctx.lineWidth=ball_radius; <br>ctx.arc(ball_x,ball_y,ball_radius,0,Math.PI*2,true); <br>ctx.fill();//note <br>ctx.fillStyle="rgb(0,0,0)"; <br>ctx.fillRect(wall_x,wall_y,wall_width,wall_height); <br>ctx.StrokeRect(box_x,box_y,box_width,box_height); <br>} <br>function init() <br>{ <br>canvas=document.getElementById('canvas'); <br>ctx=canvas.getContext('2d'); <br>draw_all(); <br>setInterval(draw_all,100); <br>setInterval(move_ball,50); <br>window.addEventListener('keydown',move_wall,false);//note <br>} <br></script>