+ * Gradient is drawn in a rectangular area, TopLeft is (-0.5, -0.5) and BottomRight is (0.5, 0.5).
+ * The outside of the entered Start Position and End Position is extended to the value of the border.
+ * Even if the range between Start Position and End Position is greater than (-0.5, -0.5) to (0.5, 0.5),
+ * only the corresponding area is drawn.