webgl added

webgl-demo.js

@@ -0,0 +1,126 @@
+//
+// start here
+//
+//
+//
+var gl = null;
+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;
+}
+
+function compileLinkProgram(vertex_source, fragment_source) {
+  const vertexShader = loadShader(gl, gl.VERTEX_SHADER, vertex_source);
+  const fragmentShader = loadShader(gl, gl.FRAGMENT_SHADER, fragment_source);
+
+  // 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;
+}
+
+function bind2DFloat32Data(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.
+  // 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);
+  const vao = gl.createVertexArray();
+  gl.bindVertexArray(vao);
+  const vertex_attrib = 0;
+  const numComponents = 2;
+  const type = gl.FLOAT; // the data in the buffer is 32bit floats
+  const normalize = false; // don't normalize
+  const stride = 0; // how many bytes to get from one set of values to the next
+  // 0 = use type and numComponents above
+  const offset = 0; // how many bytes inside the buffer to start from
+  gl.vertexAttribPointer(
+    vertex_attrib,
+    numComponents,
+    type,
+    normalize,
+    stride,
+    offset,
+  );
+
+  gl.enableVertexAttribArray(vertex_attrib);
+  return vao;
+}
+
+function main() {
+  const canvas = document.querySelector("#glcanvas");
+  // Initialize the GL context
+  gl = canvas.getContext("webgl");
+
+  // Only continue if WebGL is available and working
+  if (gl === null) {
+    alert(
+      "Unable to initialize WebGL. Your browser or machine may not support it.",
+    );
+    return;
+  }
+  const vsSource = `
+      attribute vec4 aVertexPosition;
+      void main() {
+        gl_Position = aVertexPosition;
+      }
+    `;
+  const fsSource = `
+      void main() {
+        gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0);
+      }
+    `;
+  const shaderProgram = compileLinkProgram(vsSource, fsSource);
+  const positions = [0.5, 0.5, -0.5, 0.5, 0.5, -0.5, -0.5, -0.5];
+
+  // Set clear color to black, fully opaqe
+  gl.clearColor(0.0, 0.0, 0.0, 1.0);
+  // Clear the color buffer with specified clear color
+  gl.clear(gl.COLOR_BUFFER_BIT);
+  gl.useProgram(shaderProgram);
+  {
+    const offset = 0;
+    const vertexCount = 4;
+    gl.drawArrays(gl.TRIANGLE_STRIP, offset, vertexCount);
+  }
+}
+window.load = main();