@chinhui/niivue/src/shader.js

minimal webgl2 nifti image viewer

// shader.js is taken from github user Twinklebear: https://github.com/Twinklebear/webgl-util

/**
 * @class Shader
 * @type Shader
 * @constructor
 * @param {WebGL2RenderingContext} gl
 * @param {string} vertexSrc
 * @param {string} fragmentSrc
 */
export function Shader(gl, vertexSrc, fragmentSrc) {
  var self = this;
  this.program = compileShader(gl, vertexSrc, fragmentSrc);

  var regexUniform = /uniform[^;]+[ ](\w+);/g;
  var matchUniformName = /uniform[^;]+[ ](\w+);/;

  this.uniforms = {};

  var vertexUnifs = vertexSrc.match(regexUniform);
  var fragUnifs = fragmentSrc.match(regexUniform);

  if (vertexUnifs) {
    vertexUnifs.forEach(function (unif) {
      var m = unif.match(matchUniformName);
      self.uniforms[m[1]] = -1;
    });
  }
  if (fragUnifs) {
    fragUnifs.forEach(function (unif) {
      var m = unif.match(matchUniformName);
      self.uniforms[m[1]] = -1;
    });
  }

  for (var unif in this.uniforms) {
    this.uniforms[unif] = gl.getUniformLocation(this.program, unif);
  }
}

Shader.prototype.use = function (gl) {
  gl.useProgram(this.program);
};

// Compile and link the shaders vert and frag. vert and frag should contain
// the shader source code for the vertex and fragment shaders respectively
// Returns the compiled and linked program, or null if compilation or linking failed
export var compileShader = function (gl, vert, frag) {
  var vs = gl.createShader(gl.VERTEX_SHADER);
  gl.shaderSource(vs, vert);
  gl.compileShader(vs);
  if (!gl.getShaderParameter(vs, gl.COMPILE_STATUS)) {
    alert("Vertex shader failed to compile, see console for log");
    console.log(gl.getShaderInfoLog(vs));
    return null;
  }

  var fs = gl.createShader(gl.FRAGMENT_SHADER);
  gl.shaderSource(fs, frag);
  gl.compileShader(fs);
  if (!gl.getShaderParameter(fs, gl.COMPILE_STATUS)) {
    alert("Fragment shader failed to compile, see console for log");
    console.log(gl.getShaderInfoLog(fs));
    return null;
  }

  var program = gl.createProgram();
  gl.attachShader(program, vs);
  gl.attachShader(program, fs);
  gl.linkProgram(program);
  if (!gl.getProgramParameter(program, gl.LINK_STATUS)) {
    alert("Shader failed to link, see console for log");
    console.log(gl.getProgramInfoLog(program));
    return null;
  }
  return program;
};

export var getGLExtension = function (gl, ext) {
  if (!gl.getExtension(ext)) {
    alert("Missing " + ext + " WebGL extension");
    return false;
  }
  return true;
};