Method inverseTranspose4x4

src/math/Matrices/Matrix.js:744–771

* Converts a 4×4 matrix to its 3×3 inverse transpose transform. * This is commonly used in MVMatrix to NMatrix conversions, particularly * in 3D graphics for transforming normal vectors. * * This method extracts the top-left 3×3 portion of a 4×4 matrix, inverts it, * and then transpos

({ mat4 })

   * }
   */
  inverseTranspose4x4({ mat4 }) {
    if (this.#sqDimention !== 3) {
      throw new Error('This function only works with 3×3 matrices.');
    } else {
      // Convert mat4 -> mat3 by extracting the top-left 3×3 portion
      this.matrix[0] = mat4[0];
      this.matrix[1] = mat4[1];
      this.matrix[2] = mat4[2];
      this.matrix[3] = mat4[4];
      this.matrix[4] = mat4[5];
      this.matrix[5] = mat4[6];
      this.matrix[6] = mat4[8];
      this.matrix[7] = mat4[9];
      this.matrix[8] = mat4[10];
    }

    const inverse = this.invert();
    // Check if inversion succeeded
    if (inverse) {
      inverse.transpose(this.matrix);
    } else {
      // In case of singularity, zero out the matrix
      for (let i = 0; i < 9; i++) {
        this.matrix[i] = 0;
      }
    }
    return this;
  }

  /**
   * Applies a transformation matrix to the current matrix.