4230-hw-1/Pendulum/ShapedObject.js

// PendulumComponents.js
// John Breaux  2022-06-30
// Super-class for simple, flat-color drawn primitives

"use strict";

//
// Classes
//

// ShapedObject: Super-class for simple drawn primitives
class ShapedObject {
   constructor({ color = { r: 1, g: 1, b: 1, a: 0.5 } } = {}) {
      // Set object color
      this.color = [color.r, color.g, color.b, color.a];
   }

   // Convert to Float32Array [x, y]
   vertex_array() {
      // allocate space for center.xy + vertices.xy
      var ret = new Float32Array((this.vertices.length) * 2);
      // save the vertices
      for (var i = 0; i < this.vertices.length; i++) {
         var j = 2 * i;
         ret[j] = this.vertices[i].x;
         ret[j + 1] = this.vertices[i].y;
      }
      return ret;
   }

   // Generate the index_array for the shape
   index_array() {
      var ret = new Uint8Array(this.vertices.length + 1);
      for (var i = 0; i < this.vertices.length; i++) {
         ret[i] = i
      }
      ret[this.vertices.length] = 0;
      return ret;
   }

   // Initialize the object's drawing parameters
   init(gl) {
      // Make the buffers
      this.vertexBuffer = acquire_buffer(gl);
      this.indexBuffer = acquire_buffer(gl);

      // Bind the buffers
      gl.bindBuffer(gl.ARRAY_BUFFER, this.vertexBuffer);
      gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, this.indexBuffer);

      // Write date into the buffers
      gl.bufferData(gl.ARRAY_BUFFER, this.vertex_array(), gl.STATIC_DRAW);
      gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, this.index_array(), gl.STATIC_DRAW);
   }

   // Draw the object
   draw(gl, modelMatrix, u_ModelMatrix) {
      // Bind the buffers
      gl.bindBuffer(gl.ARRAY_BUFFER, this.vertexBuffer);
      gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, this.indexBuffer);

      // Set the object's color
      var u_Color = acquire_uniform(gl, 'u_Color');
      gl.uniform4fv(u_Color, this.color);

      // get a_Position
      enable_attribute(gl, 'a_Position', 2, gl.FLOAT);

      // Pass the rotation matrix to the vertex shader
      gl.uniformMatrix4fv(u_ModelMatrix, false, modelMatrix.elements);
      // Draw the Anchor
      gl.drawElements(this.draw_primitive, this.vertices.length, gl.UNSIGNED_BYTE, 0);
   }
}

// Give me your [HeartShapedObject]