updated shader post. copy-paste from mozilla

_assets/javascript/shaderCanvas3.js

@@ -0,0 +1,301 @@
+var squareRotation = 0.0;
+
+//main();
+window.addEventListener("load", main);
+
+//
+// Start here
+//
+function main() {
+  const canvas = document.querySelector('#canvas');
+  const gl = canvas.getContext('webgl');
+
+  // If we don't have a GL context, give up now
+
+  if (!gl) {
+    alert('Unable to initialize WebGL. Your browser or machine may not support it.');
+    return;
+  }
+
+  // Vertex shader program
+
+  const vsSource = `
+    attribute vec4 aVertexPosition;
+    attribute vec4 aVertexColor;
+
+    uniform mat4 uModelViewMatrix;
+    uniform mat4 uProjectionMatrix;
+
+    varying lowp vec4 vColor;
+
+    void main(void) {
+      gl_Position = uProjectionMatrix * uModelViewMatrix * aVertexPosition;
+      vColor = aVertexColor;
+    }
+  `;
+
+  // Fragment shader program
+
+  const fsSource = `
+    varying lowp vec4 vColor;
+
+    void main(void) {
+      gl_FragColor = vColor;
+    }
+  `;
+
+  // Initialize a shader program; this is where all the lighting
+  // for the vertices and so forth is established.
+  const shaderProgram = initShaderProgram(gl, vsSource, fsSource);
+
+  // Collect all the info needed to use the shader program.
+  // Look up which attributes our shader program is using
+  // for aVertexPosition, aVevrtexColor and also
+  // look up uniform locations.
+  const programInfo = {
+    program: shaderProgram,
+    attribLocations: {
+      vertexPosition: gl.getAttribLocation(shaderProgram, 'aVertexPosition'),
+      vertexColor: gl.getAttribLocation(shaderProgram, 'aVertexColor'),
+    },
+    uniformLocations: {
+      projectionMatrix: gl.getUniformLocation(shaderProgram, 'uProjectionMatrix'),
+      modelViewMatrix: gl.getUniformLocation(shaderProgram, 'uModelViewMatrix'),
+    },
+  };
+
+  // Here's where we call the routine that builds all the
+  // objects we'll be drawing.
+  const buffers = initBuffers(gl);
+
+  var then = 0;
+
+  // Draw the scene repeatedly
+  function render(now) {
+    now *= 0.001;  // convert to seconds
+    const deltaTime = now - then;
+    then = now;
+
+    drawScene(gl, programInfo, buffers, deltaTime);
+
+    requestAnimationFrame(render);
+  }
+  requestAnimationFrame(render);
+}
+
+//
+// initBuffers
+//
+// Initialize the buffers we'll need. For this demo, we just
+// have one object -- a simple two-dimensional square.
+//
+function initBuffers(gl) {
+
+  // Create a buffer for the square's positions.
+
+  const positionBuffer = gl.createBuffer();
+
+  // Select the positionBuffer as the one to apply buffer
+  // operations to from here out.
+
+  gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
+
+  // Now create an array of positions for the square.
+
+  const positions = [
+     1.0,  1.0,
+    -1.0,  1.0,
+     1.0, -1.0,
+    -1.0, -1.0,
+  ];
+
+  // Now pass the list of positions into WebGL to build the
+  // shape. We do this by creating a Float32Array from the
+  // JavaScript array, then use it to fill the current buffer.
+
+  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(positions), gl.STATIC_DRAW);
+
+  // Now set up the colors for the vertices
+
+  const colors = [
+    1.0,  0.5,  1.0,  1.0,    // white
+    1.0,  0.6,  1.0,  1.0,    // red
+    1.0,  0.7,  1.0,  1.0,    // green
+    1.0,  0.3,  1.0,  1.0,    // blue
+  ];
+
+  const colorBuffer = gl.createBuffer();
+  gl.bindBuffer(gl.ARRAY_BUFFER, colorBuffer);
+  gl.bufferData(gl.ARRAY_BUFFER, new Float32Array(colors), gl.STATIC_DRAW);
+
+  return {
+    position: positionBuffer,
+    color: colorBuffer,
+  };
+}
+
+//
+// Draw the scene.
+//
+function drawScene(gl, programInfo, buffers, deltaTime) {
+  gl.clearColor(0.0, 0.0, 0.0, 1.0);  // Clear to black, fully opaque
+  gl.clearDepth(1.0);                 // Clear everything
+  gl.enable(gl.DEPTH_TEST);           // Enable depth testing
+  gl.depthFunc(gl.LEQUAL);            // Near things obscure far things
+
+  // Clear the canvas before we start drawing on it.
+
+  gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
+
+  // Create a perspective matrix, a special matrix that is
+  // used to simulate the distortion of perspective in a camera.
+  // Our field of view is 45 degrees, with a width/height
+  // ratio that matches the display size of the canvas
+  // and we only want to see objects between 0.1 units
+  // and 100 units away from the camera.
+
+  const fieldOfView = 45 * Math.PI / 180;   // in radians
+  const aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
+  const zNear = 0.1;
+  const zFar = 100.0;
+  const projectionMatrix = mat4.create();
+
+  // note: glmatrix.js always has the first argument
+  // as the destination to receive the result.
+  mat4.perspective(projectionMatrix,
+                   fieldOfView,
+                   aspect,
+                   zNear,
+                   zFar);
+
+  // Set the drawing position to the "identity" point, which is
+  // the center of the scene.
+  const modelViewMatrix = mat4.create();
+
+  // Now move the drawing position a bit to where we want to
+  // start drawing the square.
+
+  mat4.translate(modelViewMatrix,     // destination matrix
+                 modelViewMatrix,     // matrix to translate
+                 [-0.0, 0.0, -6.0]);  // amount to translate
+  mat4.rotate(modelViewMatrix,  // destination matrix
+              modelViewMatrix,  // matrix to rotate
+              squareRotation,   // amount to rotate in radians
+              [0, 0, 1]);       // axis to rotate around
+
+  // Tell WebGL how to pull out the positions from the position
+  // buffer into the vertexPosition attribute
+  {
+    const numComponents = 2;
+    const type = gl.FLOAT;
+    const normalize = false;
+    const stride = 0;
+    const offset = 0;
+    gl.bindBuffer(gl.ARRAY_BUFFER, buffers.position);
+    gl.vertexAttribPointer(
+        programInfo.attribLocations.vertexPosition,
+        numComponents,
+        type,
+        normalize,
+        stride,
+        offset);
+    gl.enableVertexAttribArray(
+        programInfo.attribLocations.vertexPosition);
+  }
+
+  // Tell WebGL how to pull out the colors from the color buffer
+  // into the vertexColor attribute.
+  {
+    const numComponents = 4;
+    const type = gl.FLOAT;
+    const normalize = false;
+    const stride = 0;
+    const offset = 0;
+    gl.bindBuffer(gl.ARRAY_BUFFER, buffers.color);
+    gl.vertexAttribPointer(
+        programInfo.attribLocations.vertexColor,
+        numComponents,
+        type,
+        normalize,
+        stride,
+        offset);
+    gl.enableVertexAttribArray(
+        programInfo.attribLocations.vertexColor);
+  }
+
+  // Tell WebGL to use our program when drawing
+
+  gl.useProgram(programInfo.program);
+
+  // Set the shader uniforms
+
+  gl.uniformMatrix4fv(
+      programInfo.uniformLocations.projectionMatrix,
+      false,
+      projectionMatrix);
+  gl.uniformMatrix4fv(
+      programInfo.uniformLocations.modelViewMatrix,
+      false,
+      modelViewMatrix);
+
+  {
+    const offset = 0;
+    const vertexCount = 4;
+    gl.drawArrays(gl.TRIANGLE_STRIP, offset, vertexCount);
+  }
+
+  // Update the rotation for the next draw
+
+  squareRotation += deltaTime;
+}
+
+//
+// Initialize a shader program, so WebGL knows how to draw our data
+//
+function initShaderProgram(gl, vsSource, fsSource) {
+  const vertexShader = loadShader(gl, gl.VERTEX_SHADER, vsSource);
+  const fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fsSource);
+
+  // Create the shader program
+
+  const shaderProgram = gl.createProgram();
+  gl.attachShader(shaderProgram, vertexShader);
+  gl.attachShader(shaderProgram, fragmentShader);
+  gl.linkProgram(shaderProgram);
+
+  // If creating the shader program failed, alert
+
+  if (!gl.getProgramParameter(shaderProgram, gl.LINK_STATUS)) {
+    alert('Unable to initialize the shader program: ' + gl.getProgramInfoLog(shaderProgram));
+    return null;
+  }
+
+  return shaderProgram;
+}
+
+//
+// creates a shader of the given type, uploads the source and
+// compiles it.
+//
+function loadShader(gl, type, source) {
+  const shader = gl.createShader(type);
+
+  // Send the source to the shader object
+
+  gl.shaderSource(shader, source);
+
+  // Compile the shader program
+
+  gl.compileShader(shader);
+
+  // See if it compiled successfully
+
+  if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS)) {
+    alert('An error occurred compiling the shaders: ' + gl.getShaderInfoLog(shader));
+    gl.deleteShader(shader);
+    return null;
+  }
+
+  return shader;
+}
+

_posts/2020-12-18-shader.markdown

@@ -4,54 +4,8 @@ title: "Shader fun"
 date: 2020-12-28
 categories: design
 ---
-<canvas id="canvas" width="1080" height="1080" style="border:1px solid white;
+<canvas id="canvas" width="1080" height="1080" style="//border:1px solid white;
 width:100%;"></canvas>
 
-<script id="node-vertex-shader" type="x-shader/x-vertex">
-  uniform vec2 u_resolution;
-  attribute vec2 a_position;
-  attribute vec2 a_center;
-  attribute float a_radius;
-
-  varying vec2 center;
-  varying vec2 resolution;
-  varying float radius;
-   
-  void main() {
-    vec2 clipspace = a_position / u_resolution * 2.0 - 1.0;
-    gl_Position = vec4(clipspace * vec2(1, -1), 0, 1);
-
-    radius = a_radius;
-    center = a_center;
-    resolution = u_resolution;
-  }
-</script>
-
-<script id="node-fragment-shader" type="x-shader/x-fragment">
-
-  precision mediump float;
-
-  varying vec2 center;
-  varying vec2 resolution;
-  varying float radius;
-
-  void main() {
-    vec4 color0 = vec4(0.0, 0.0, 0.0, 0.0);
-
-    float x = gl_FragCoord.x;
-    float y = resolution[1] - gl_FragCoord.y;
-
-    float dx = center[0] - x;
-    float dy = center[1] - y;
-    float distance = sqrt(dx*dx + dy*dy);
-
-    if ( distance < radius )
-      gl_FragColor = vec4(1.0, 0.5, 0.0, 1.0);
-    else 
-      gl_FragColor = color0;
-
-  }
-</script>
-
-
-{% asset shaderCanvas2.js %}
+<script src="https://cdnjs.cloudflare.com/ajax/libs/gl-matrix/2.8.1/gl-matrix-min.js" integrity="sha512-zhHQR0/H5SEBL3Wn6yYSaTTZej12z0hVZKOv3TwCUXT1z5qeqGcXJLLrbERYRScEDDpYIJhPC1fk31gqR783iQ==" crossorigin="anonymous" defer=""></script>
+{% asset shaderCanvas3.js %}