_init() {

		const gl = this.gl;

		// Store only WebGL constants here.

		equationToGL = {
			[ AddEquation ]: gl.FUNC_ADD,
			[ SubtractEquation ]: gl.FUNC_SUBTRACT,
			[ ReverseSubtractEquation ]: gl.FUNC_REVERSE_SUBTRACT
		};

		factorToGL = {
			[ ZeroFactor ]: gl.ZERO,
			[ OneFactor ]: gl.ONE,
			[ SrcColorFactor ]: gl.SRC_COLOR,
			[ SrcAlphaFactor ]: gl.SRC_ALPHA,
			[ SrcAlphaSaturateFactor ]: gl.SRC_ALPHA_SATURATE,
			[ DstColorFactor ]: gl.DST_COLOR,
			[ DstAlphaFactor ]: gl.DST_ALPHA,
			[ OneMinusSrcColorFactor ]: gl.ONE_MINUS_SRC_COLOR,
			[ OneMinusSrcAlphaFactor ]: gl.ONE_MINUS_SRC_ALPHA,
			[ OneMinusDstColorFactor ]: gl.ONE_MINUS_DST_COLOR,
			[ OneMinusDstAlphaFactor ]: gl.ONE_MINUS_DST_ALPHA
		};

		const scissorParam = gl.getParameter( gl.SCISSOR_BOX );
		const viewportParam = gl.getParameter( gl.VIEWPORT );

		this.currentScissor = new Vector4().fromArray( scissorParam );
		this.currentViewport = new Vector4().fromArray( viewportParam );

		this._tempVec4 = new Vector4();

	}
Inits the state of the utility.

@private