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I can't find out what I am missing here, why do I get this error? Uncaught ReferenceError: createShaderFromScriptElement is not defined

I got this from a common tutorial and just pasted it. Browsers: Firefox and Chrome --> same error at both browsers

    <!DOCTYPE HTML>
<html lang="en">
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
        <title>Zooming via HTML5 Canvas Context</title>
    </head>
    <body>

        <canvas id="canvas" width="200" height="200"></canvas>

        <script id="2d-vertex-shader" type="x-shader/x-vertex">
            attribute vec2 a_position;

            void main() {
            gl_Position = vec4(a_position, 0, 1);
            }
        </script>

        <script id="2d-fragment-shader" type="x-shader/x-fragment">
            void main() {
            gl_FragColor = vec4(0,1,0,1);  // green
            }
        </script>

        <script>
            window.onload = function() {
                // Get A WebGL context
                var canvas = document.getElementById("canvas");
                var gl = canvas.getContext("experimental-webgl");

                // setup a GLSL program

                var vertexShader = createShaderFromScriptElement(gl, "2d-vertex-shader");
                var fragmentShader = createShaderFromScriptElement(gl, "2d-fragment-shader");
                var program = createProgram(gl, [vertexShader, fragmentShader]);
                gl.useProgram(program);

                // look up where the vertex data needs to go.
                var positionLocation = gl.getAttribLocation(program, "a_position");

                // Create a buffer and put a single clipspace rectangle in
                // it (2 triangles)
                var buffer = gl.createBuffer();
                gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
                gl.bufferData(
                        gl.ARRAY_BUFFER,
                        new Float32Array([
                            -1.0, -1.0,
                            1.0, -1.0,
                            -1.0,  1.0,
                            -1.0,  1.0,
                            1.0, -1.0,
                            1.0,  1.0]),
                        gl.STATIC_DRAW);
                gl.enableVertexAttribArray(positionLocation);
                gl.vertexAttribPointer(positionLocation, 2, gl.FLOAT, false, 0, 0);

                // draw
                gl.drawArrays(gl.TRIANGLES, 0, 6);
            }

        </script>


    </body>
</html>
4

1 回答 1

8

createShaderFromScript是外部脚本的一部分，而不是内置的。

无论您正在查看什么演示，都可能包含一个 webgl-utils 文件，例如：

http://greggman.github.com/webgl-fundamentals/webgl/resources/webgl-utils.js

它定义了一个createShaderFromScript.

于 2012-11-13T14:46:05.323 回答