mdx-m3-viewer/src/viewer/handlers/m3/region.js

A browser WebGL model viewer. Mainly focused on models of the games Warcraft 3 and Starcraft 2.

/**
 * An M3 region.
 */
export default class M3Region {
  /**
   * @param {M3Model} model
   * @param {M3ParserRegion} region
   * @param {Uint16Array} triangles
   * @param {Uint16Array} elementArray
   * @param {number} offset
   */
  constructor(model, region, triangles, elementArray, offset) {
    let firstVertexIndex = region.firstVertexIndex;
    let triangleIndicesCount = region.triangleIndicesCount;
    let firstTriangleIndex = region.firstTriangleIndex;

    // Note for implementors: the one original vertex indices array could be used with access to the base-vertex draw elements function.
    // See https://www.opengl.org/sdk/docs/man3/xhtml/glDrawElementsBaseVertex.xml
    // firstTriangleIndex is the indices offset.
    // firstVertexIndex is the base vertex.
    for (let i = 0; i < triangleIndicesCount; i++) {
      elementArray[offset + i] = triangles[firstTriangleIndex + i] + firstVertexIndex;
    }

    this.gl = model.viewer.gl;
    this.firstBoneLookupIndex = region.firstBoneLookupIndex;
    this.boneWeightPairsCount = region.boneWeightPairsCount;
    this.offset = offset * 2;
    this.verticesCount = region.verticesCount;
    this.elements = triangleIndicesCount;
  }

  /**
   * @param {ShaderProgram} shader
   * @param {number} instances
   */
  render(shader, instances) {
    let gl = this.gl;

    gl.uniform1f(shader.uniforms.u_firstBoneLookupIndex, this.firstBoneLookupIndex);
    gl.uniform1f(shader.uniforms.u_boneWeightPairsCount, this.boneWeightPairsCount);

    gl.extensions.instancedArrays.drawElementsInstancedANGLE(gl.TRIANGLES, this.elements, gl.UNSIGNED_SHORT, this.offset, instances);
  }

  /**
   * @return {number}
   */
  getPolygonCount() {
    return this.elements / 3;
  }
}