클릭을 통한 청소
랜덤 색을 가진 랜더링 컨텍스트를 청소
이 간단한 예시는 어떻게 유저 인터페이스와 WebGL를 결합할지에 대한 설명을 제공합니다. 유저가 캔버스 혹은 버튼을 클릭할 때 마다, 캔버스는 랜덤으로 선택된 색으로 초기화됩니다.
어떻게 내장된 WebGL 기능이 이벤트 핸들러의 내부를 부르는 지를 주목하세요.
html
<p>
A very simple WebGL program that still shows some color and user interaction.
</p>
<p>
You can repeatedly click the empty canvas or the button below to change color.
</p>
<canvas id="canvas-view"
>Your browser does not seem to support HTML5 canvas.</canvas
>
<button id="color-switcher">Press here to switch color</button>
css
body {
text-align: center;
}
canvas {
display: block;
width: 280px;
height: 210px;
margin: auto;
padding: 0;
border: none;
background-color: black;
}
button {
display: inline-block;
font-size: inherit;
margin: auto;
padding: 0.6em;
}
js
window.addEventListener(
"load",
function setupWebGL(evt) {
"use strict";
// Cleaning after ourselves. The event handler removes
// itself, because it only needs to run once.
window.removeEventListener(evt.type, setupWebGL, false);
// Adding the same click event handler to both canvas and
// button.
var canvas = document.querySelector("#canvas-view");
var button = document.querySelector("#color-switcher");
canvas.addEventListener("click", switchColor, false);
button.addEventListener("click", switchColor, false);
// A variable to hold the WebGLRenderingContext.
var gl;
// The click event handler.
function switchColor() {
// Referring to the externally defined gl variable.
// If undefined, try to obtain the WebGLRenderingContext.
// If failed, alert user of failure.
// Otherwise, initialize the drawing buffer (the viewport).
if (!gl) {
gl =
canvas.getContext("webgl") || canvas.getContext("experimental-webgl");
if (!gl) {
alert(
"Failed to get WebGL context.\n" +
"Your browser or device may not support WebGL.",
);
return;
}
gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight);
}
// Get a random color value using a helper function.
var color = getRandomColor();
// Set the clear color to the random color.
gl.clearColor(color[0], color[1], color[2], 1.0);
// Clear the context with the newly set color. This is
// the function call that actually does the drawing.
gl.clear(gl.COLOR_BUFFER_BIT);
}
// Random color helper function.
function getRandomColor() {
return [Math.random(), Math.random(), Math.random()];
}
},
false,
);
이 예시 코드는 GitHub에서도 확인 가능합니다.