4230-hw-1/Pendulum/common.js

// common.js
// John Breaux  2022-06-30
// Common functions and global variables for Pendulum.js

"use strict";

//
// Global variables
//

// Point size of the anchor
var POINT_SIZE = 5;
// Radius of the bob
var BOB_RADIUS = 0.1;
// length of the wire
var PEN_LENGTH = 0.8;
// Rotation angle (degrees/second)
var A_VELOCITY = 45.0;

//
// Common functions:
//

//  acquire_buffer: Get a vertex buffer object from gl
function acquire_buffer(gl) {
   // Create a buffer object
   var vertexBuffer = gl.createBuffer();
   if (!vertexBuffer) {
      console.log('Failed to create the buffer object');
      return -1;
   }
   return vertexBuffer;
}

function enable_attribute(gl, name, size, type) {
   // Acquire a reference to named attr
   var attr = gl.getAttribLocation(gl.program, name);
   if (attr < 0) {
      console.log(`Failed to get the storage location of ${name}`);
      return -1;
   }
   gl.vertexAttribPointer(attr, size, type, false, 0, 0);
   // Switch GL state machine to use named attr
   gl.enableVertexAttribArray(attr);
}

function acquire_uniform(gl, name) {
   // Acquire a reference to named attr
   var ret = gl.getUniformLocation(gl.program, name);
   if (!ret) {
      console.log(`Failed to get the storage location of ${name}`);
      return -1;
   }
   return ret;
}