code: public Matrix4f setOrtho2D(float left, float right, float bottom, float top) {
          if ((properties & PROPERTY_IDENTITY) == 0)
              MemUtil.INSTANCE.identity(this);
          this._m00(2.0f / (right - left));
          this._m11(2.0f / (top - bottom));
          this._m22(-1.0f);
          this._m30((right + left) / (left - right));
          this._m31((top + bottom) / (bottom - top));
          _properties(PROPERTY_AFFINE);
          return this;
      }
docs: Set this matrix to be an orthographic projection transformation for a right-handed coordinate system.
  <p>
  This method is equivalent to calling {@link #setOrtho(float, float, float, float, float, float) setOrtho()} with
  <code>zNear=-1</code> and <code>zFar=+1</code>.
  <p>
  In order to apply the orthographic projection to an already existing transformation,
  use {@link #ortho2D(float, float, float, float) ortho2D()}.
  <p>
  Reference: <a href="http://www.songho.ca/opengl/gl_projectionmatrix.html#ortho">http://www.songho.ca</a>
  
  @see #setOrtho(float, float, float, float, float, float)
  @see #ortho2D(float, float, float, float)
  
  @param left
  the distance from the center to the left frustum edge
  @param right
  the distance from the center to the right frustum edge
  @param bottom
  the distance from the center to the bottom frustum edge
  @param top
  the distance from the center to the top frustum edge
  @return this