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GlBoilerplate.js 3.31 KiB
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    //from http://webglfundamentals.org/webgl/lessons/webgl-boilerplate.html
    
    /**
     * Creates and compiles a shader.
     *
     * @param {!WebGLRenderingContext} gl The WebGL Context.
     * @param {string} shaderSource The GLSL source code for the shader.
     * @param {number} shaderType The type of shader, VERTEX_SHADER or
     *     FRAGMENT_SHADER.
     * @return {!WebGLShader} The shader.
     */
    function compileShader(gl, shaderSource, shaderType) {
      // Create the shader object
      var shader = gl.createShader(shaderType);
    
      // Set the shader source code.
      gl.shaderSource(shader, shaderSource);
    
      // Compile the shader
      gl.compileShader(shader);
    
      // Check if it compiled
      var success = gl.getShaderParameter(shader, gl.COMPILE_STATUS);
      if (!success) {
        // Something went wrong during compilation; get the error
        throw "could not compile shader:" + gl.getShaderInfoLog(shader);
      }
    
      return shader;
    }
    
    /**
     * Creates a program from 2 shaders.
     *
     * @param {!WebGLRenderingContext) gl The WebGL context.
     * @param {!WebGLShader} vertexShader A vertex shader.
     * @param {!WebGLShader} fragmentShader A fragment shader.
     * @return {!WebGLProgram} A program.
     */
    function createProgram(gl, vertexShader, fragmentShader) {
      // create a program.
      var program = gl.createProgram();
    
      // attach the shaders.
      gl.attachShader(program, vertexShader);
      gl.attachShader(program, fragmentShader);
    
      // link the program.
      gl.linkProgram(program);
    
      // Check if it linked.
      var success = gl.getProgramParameter(program, gl.LINK_STATUS);
      if (!success) {
          // something went wrong with the link
          throw ("program filed to link:" + gl.getProgramInfoLog (program));
      }
    
      return program;
    }
    
    /**
     * Creates a shader from the content of a script tag.
     *
     * @param {!WebGLRenderingContext} gl The WebGL Context.
     * @param {string} scriptId The id of the script tag.
     * @param {string} opt_shaderType. The type of shader to create.
     *     If not passed in will use the type attribute from the
     *     script tag.
     * @return {!WebGLShader} A shader.
     */
    function createShaderFromScript(gl, scriptId, opt_shaderType) {
      // look up the script tag by id.
      var shaderScript = document.getElementById(scriptId);
      if (!shaderScript) {
        throw("*** Error: unknown script element" + scriptId);
      }
    
      // extract the contents of the script tag.
      var shaderSource = shaderScript.text;
    
      // If we didn't pass in a type, use the 'type' from
      // the script tag.
      if (!opt_shaderType) {
        if (shaderScript.type == "x-shader/x-vertex") {
          opt_shaderType = gl.VERTEX_SHADER;
        } else if (shaderScript.type == "x-shader/x-fragment") {
          opt_shaderType = gl.FRAGMENT_SHADER;
        } else if (!opt_shaderType) {
          throw("*** Error: shader type not set");
        }
      }
    
      return compileShader(gl, shaderSource, opt_shaderType);
    }
    
    /**
     * Creates a program from 2 script tags.
     *
     * @param {!WebGLRenderingContext} gl The WebGL Context.
     * @param {string} vertexShaderId The id of the vertex shader script tag.
     * @param {string} fragmentShaderId The id of the fragment shader script tag.
     * @return {!WebGLProgram} A program
     */
    function createProgramFromScripts(
        gl, vertexShaderId, fragmentShaderId) {
      var vertexShader = createShaderFromScript(gl, vertexShaderId);
      var fragmentShader = createShaderFromScript(gl, fragmentShaderId);
      return createProgram(gl, vertexShader, fragmentShader);
    }