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Introduction to WebGL @Krzychukula
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Plan 1. Intro 2. How it all works 3. Triangle in WebGL 4. Multiple colours 5. Our own Shadertoy 6. Learn
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Disclaimer: mental models over correctness
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NO SHINY DEMOS
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ASK QUESTIONS!
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Data Visualisation
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Shadertoy
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2. How it all works?
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Back in the old days…
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Graphic Card
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Map Reduce?
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What is WebGL?
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History
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Shaders
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Vertex Fragment
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Vertex Shader Fragment Shader
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It has to be FAST
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Vertex Shader void main() { gl_Position = vec4(0.0, 0.0, 0.0, 1.0); }
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Vertex Shader attribute vec4 a_Position; void main() { gl_Position = a_Position; }
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Fragment Shader void main() { gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0); }
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Fragment Shader uniform vec4 u_Color; void main() { gl_FragColor = u_Color; }
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But… What about JS?
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Context var gl = canvas.getContext("webgl");
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Compile Vertex Shader var vertexShader = gl.createShader(gl.VERTEX_SHADER) gl.shaderSource(vertexShader, ` void main() { … } `) gl.compileShader(vertexShader)
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Compile Fragment Shader var fragShader = gl.createShader(gl.FRAGMENT_SHADER) gl.shaderSource(fragShader, ` void main() { … } `) gl.compileShader(fragShader)
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Program var program = gl.createProgram() gl.attachShader(program, vertexShader) gl.attachShader(program, fragmentShader) gl.linkProgram(program)
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u_Color var u_Color = gl.getUniformLocation(program, ‘u_Color’); gl.uniform4fv(u_Color, [0.0, 1.0, 0.0, 1.0]);
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Fragment Shader uniform vec4 u_Color; void main() { gl_FragColor = u_Color; }
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1 -1 1
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-0.5, -0.5
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-0.5, -0.5 0.5, -0.5
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-0.5, -0.5 0, 0.5 0.5, -0.5
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gl_Position = vec4(0.0, 0.5, 0.0, 1.0); -0.5, -0.5 0, 0.5 -0.5, 0.5
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gl_Position = vec4(0.0, 0.5, 0.0, 1.0); gl_Position = vec4(-0.5, -0.5, 0.0, 1.0); gl_Position = vec4(0.5, -0.5, 0.0, 1.0); -0.5, -0.5 0, 0.5 -0.5, 0.5
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var positions = new Float32Array([ -0.5, -0.5, 0.0, 1.0, 0.5, -0.5, 0.0, 1.0, 0.0, 0.5, 0.0, 1.0 ]);
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Buffers
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var buffer = gl.createBuffer() gl.bindBuffer(gl.ARRAY_BUFFER, buffer) gl.bufferData(gl.ARRAY_BUFFER, positions, gl.STATIC_DRAW)
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var positions = new Float32Array([ 0.0, 0.5, 0.0, 1.0, -0.5, -0.5, 0.0, 1.0, 0.5, -0.5, 0.0, 1.0 ]);
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var a_Position = gl.getAttribLocation(program, ‘a_Position') gl.enableVertexAttribArray(a_Position) gl.vertexAttribPointer(a_Position, 4, gl.FLOAT, false, 0, 0)
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gl.drawArrays(gl.TRIANGLES, 0, 3)
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Fragment Shader attribute vec4 a_Color; void main() { gl_FragColor = a_Color; }
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varying Vertex Shaders Fragment Shaders attributes
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Vertex Shader attribute vec4 a_Position; attribute vec4 a_Color; varying vec4 v_Color; void main() { gl_Position = a_Position; v_Color = a_Color; }
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Vertex Shader void main(vec4 a_Position, vec4 a_Color) { return { gl_Position: a_Position, v_Color: a_Color }; }
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v_Color = vec4(1.0, 0.0, 0.0, 1.0); v_Color = vec4(0.0, 1.0, 0.0, 1.0); v_Color = vec4(0.0, 0.0, 1.0, 1.0);
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What about the middle?
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Fragment Shader varying vec4 v_Color; void main() { gl_FragColor = v_Color; }
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var colors = new Float32Array([ 1.0, 0.0, 0.0, 1.0, 0.0, 1.0, 0.0, 1.0, 0.0, 0.0, 1.0, 1.0 ]);
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var buffer = gl.createBuffer() gl.bindBuffer(gl.ARRAY_BUFFER, buffer) gl.bufferData(gl.ARRAY_BUFFER, colors, gl.STATIC_DRAW)
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var a_Color = gl.getAttribLocation(program, ‘a_Color') gl.enableVertexAttribArray(a_Color) gl.vertexAttribPointer(a_Color, 4, gl.FLOAT, false, 0, 0)
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gl.drawArrays(gl.TRIANGLES, 0, 3)
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Shadertoy
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-1, -1 -1, 1 1, 1
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-1, -1 1, -1 1, 1
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var vertices = new Float32Array([ // X, Y, -1.0, 1.0, 1.0, 1.0, -1.0, -1.0, -1.0, -1.0, 1.0, 1.0, 1.0, -1.0, ]) In JavaScript
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-1, -1 1, -1 1, 1
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void mainImage( out vec4 fragColor, in vec2 fragCoord ) { fragColor = vec4(0.0,0.0,1.0,1.0); }
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out vec4 fragColor
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in vec2 fragCoord
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in vec2 iResolution
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in float iTime
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void mainImage( out vec4 fragColor, in vec2 fragCoord ) { vec2 uv = fragCoord.xy / iResolution.xy; fragColor = vec4(uv,0.5+0.5*sin(iTime),1.0); }
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void mainImage( out vec4 fragColor, in vec2 fragCoord ) { vec2 uv = fragCoord.xy / iResolution.xy; fragColor = vec4(uv, 0.5+0.5*sin(iTime),1.0); }
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fragColor = vec4(uv.r, uv.g, 1.0, 1.0);
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void mainImage( out vec4 fragColor, in vec2 fragCoord ) { vec2 uv = fragCoord.xy / iResolution.xy; fragColor = vec4(uv, 0.5+0.5*sin(iTime), 1.0); }
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Demo?
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What to learn from?
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WebGL Beginner’s Guide Diego Cantor & Brandon Jones
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Interactive 3D Graphics Eric Haines & Gundega Dekena
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WebGL Programming Guide Kouichi Matsuda & Rodger Lea
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The End @Krzychukula
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https:/ /hacks.mozilla.org/2017 /01/webgl-2-lands-in-firefox/ https:/ /www.chromeexperiments.com/globe https:/ /handmadehero.org/ https:/ /codepen.io/krzychukula/pen/qmZaMz?editors=0010 Triangle https:/ /codepen.io/krzychukula/pen/OmXgKe?editors=0010 Triangle 3 colors https:/ /codepen.io/krzychukula/pen/OmXgKe?editors=0010 Triangle 3 colors in one buffer https:/ /codepen.io/krzychukula/pen/qVrLww Similar to new Shadertoy in WebGL https:/ /www.shadertoy.com/new https:/ /www.packtpub.com/game-development/webgl-beginners-guide https:/ /www.udacity.com/course/interactive-3d-graphics--cs291 https:/ /sites.google.com/site/webglbook/