 				&prevPos,
 				mtxs);
 
+			if (x == 0 && y == 0) {
+				centerPrevPos = prevPos;
+			}
+
 			// [0, 1]͈͓̔ɓĂ邩.
 			bool isInsideX = (0.0 <= prevPos.x) && (prevPos.x <= 1.0);
 			bool isInsideY = (0.0 <= prevPos.y) && (prevPos.y <= 1.0);

		float lum = AT_NAME::color::luminance(curColor.x, curColor.y, curColor.z);
		float3 centerMoment = make_float3(lum * lum, lum, 0);

		// Õt[̃NbvԍWvZ.
		aten::vec4 prevPos;
		computePrevScreenPos(

	static const float zThreshold = 0.05f;
	static const float nThreshold = 0.98f;

	aten::vec4 centerPrevPos;

	for (int y = -1; y <= 1; y++) {
		for (int x = -1; x <= 1; x++) {
			int xx = clamp(ix + x, 0, width - 1);
