Avoid shadow flicker at certain angles (#12961)

Change the way look direction and camera position are quantized when calculating light frustum

2 files changed, 21 insertions, 7 deletions

diff --git a/src/client/shadows/dynamicshadows.cpp b/src/client/shadows/dynamicshadows.cpp
index 9f26ba94a..80db64286 100644
--- a/src/client/shadows/dynamicshadows.cpp
+++ b/src/client/shadows/dynamicshadows.cpp
@@ -41,10 +41,16 @@ static v3f quantizeDirection(v3f direction, float step)
 
 void DirectionalLight::createSplitMatrices(const Camera *cam)
 {
-	const float DISTANCE_STEP = BS * 2.0; // 2 meters
+	static const float COS_15_DEG = 0.965926f;
 	v3f newCenter;
-	v3f look = cam->getDirection();
-	look = quantizeDirection(look, M_PI / 12.0); // 15 degrees
+	v3f look = cam->getDirection().normalize();
+
+	// if current look direction is < 15 degrees away from the captured
+	// look direction then stick to the captured value, otherwise recapture.
+	if (look.dotProduct(last_look) >= COS_15_DEG)
+		look = last_look;
+	else
+		last_look = look;
 
 	// camera view tangents
 	float tanFovY = tanf(cam->getFovY() * 0.5f);
@@ -56,10 +62,14 @@ void DirectionalLight::createSplitMatrices(const Camera *cam)
 
 	// adjusted camera positions
 	v3f cam_pos_world = cam->getPosition();
-	cam_pos_world = v3f(
-			floor(cam_pos_world.X / DISTANCE_STEP) * DISTANCE_STEP,
-			floor(cam_pos_world.Y / DISTANCE_STEP) * DISTANCE_STEP,
-			floor(cam_pos_world.Z / DISTANCE_STEP) * DISTANCE_STEP);
+
+	// if world position is less than 1 block away from the captured
+	// world position then stick to the captured value, otherwise recapture.
+	if (cam_pos_world.getDistanceFromSQ(last_cam_pos_world) < BS * BS)
+		cam_pos_world = last_cam_pos_world;
+	else
+		last_cam_pos_world = cam_pos_world;
+
 	v3f cam_pos_scene = v3f(cam_pos_world.X - cam->getOffset().X * BS,
 			cam_pos_world.Y - cam->getOffset().Y * BS,
 			cam_pos_world.Z - cam->getOffset().Z * BS);
diff --git a/src/client/shadows/dynamicshadows.h b/src/client/shadows/dynamicshadows.h
index 6e9d96b15..f592ec077 100644
--- a/src/client/shadows/dynamicshadows.h
+++ b/src/client/shadows/dynamicshadows.h
@@ -114,6 +114,10 @@ private:
 
 	v3f pos;
 	v3f direction{0};
+
+	v3f last_cam_pos_world{0,0,0};
+	v3f last_look{0,1,0};
+
 	shadowFrustum shadow_frustum;
 	shadowFrustum future_frustum;
 	bool dirty{false};