51 lines
1.9 KiB
JavaScript
51 lines
1.9 KiB
JavaScript
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// STEP 1: Prepare the canvas and get WebGL context
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var vertShaderSource = document.getElementById("vertex-shader").text;
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var fragShaderSource = document.getElementById("fragment-shader").text;
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var canvas = document.getElementById('shader-canvas');
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var gl = canvas.getContext('webgl', {
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antialias: false,
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depth: false
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});
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// STEP 2: define geometry and store it in buffer objects
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var verticies = [-1.0, 1.0, -1.0, -1.0, 1.0, -1.0, 1.0, 1.0];
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var vertex_buffer = gl.createBuffer();
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gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer);
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gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(verticies), gl.STATIC_DRAW);
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gl.bindBuffer(gl.ARRAY_BUFFER, null)
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// STEP 3: Create and compile shader programs
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// Vert shader:
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//var vertCode =
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// 'attribute vec2 coordinates;' +
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// 'void main(void) {' +
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// ' gl_Position = vec4(coordinates, 0.0, 1.0);' +
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// '}';
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var vertCode = vertShaderSource;
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var vertShader = gl.createShader(gl.VERTEX_SHADER);
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gl.shaderSource(vertShader, vertCode);
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gl.compileShader(vertShader);
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// Frag shader:
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// var fragCode = 'void main(void) {' +
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// 'gl_FragColor = vec4(0.0, 0.3, 0.5, 1.0);' +
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// '}';
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var fragCode = fragShaderSource;
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var fragShader = gl.createShader(gl.FRAGMENT_SHADER);
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gl.shaderSource(fragShader, fragCode);
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gl.compileShader(fragShader);
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// combine shaders:
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var shaderProgram = gl.createProgram();
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gl.attachShader(shaderProgram, vertShader);
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gl.attachShader(shaderProgram, fragShader);
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gl.linkProgram(shaderProgram);
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gl.useProgram(shaderProgram);
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// STEP 4: Associate the shader program to buffer objects
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gl.bindBuffer(gl.ARRAY_BUFFER, vertex_buffer);
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var coord = gl.getAttribLocation(shaderProgram, "coordinates");
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gl.vertexAttribPointer(coord, 2, gl.FLOAT, false, 0, 0);
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gl.enableVertexAttribArray(coord);
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// STEP 5: Draw the object:
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gl.clearColor(0.0, 0.0, 0.0, 1.0);
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gl.enable(gl.DEPTH_TEST);
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gl.clear(gl.COLOR_BUFFER_BIT);
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gl.viewport(0, 0, canvas.width, canvas.height);
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gl.drawArrays(gl.TRIANGLE_FAN, 0, 4);
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