Fix aligners taking beams from sides they shouldn't take a beam from

src/main/java/com/simibubi/create/content/optics/Beam.java

@@ -8,10 +8,12 @@ import java.util.Set;
 import javax.annotation.Nullable;
 
 import com.mojang.blaze3d.matrix.MatrixStack;
+import com.simibubi.create.foundation.utility.Iterate;
 import com.simibubi.create.foundation.utility.VecHelper;
 
 import net.minecraft.client.renderer.IRenderTypeBuffer;
 import net.minecraft.item.DyeColor;
+import net.minecraft.util.Direction;
 import net.minecraft.util.math.BlockPos;
 import net.minecraft.util.math.vector.Vector3d;
 import net.minecraft.world.World;
@@ -122,4 +124,36 @@ public class Beam extends ArrayList<BeamSegment> {
 	public Beam getParent() {
 		return parent;
 	}
+
+	@Nullable
+	public Direction getBlockEnterFace(BlockPos blockPos) {
+		Vector3d beamDir = getDirection();
+		if (beamDir == null)
+			return null;
+		Vector3d pos = VecHelper.getCenterOf(blockPos);
+
+		Direction minDir = null;
+		double lambda = Double.MAX_VALUE;
+
+		for (Direction testDir : Iterate.directions) {
+			Vector3d faceNormal = Vector3d.of(testDir.getDirectionVec());
+			Vector3d posOnSide = faceNormal.scale(.5)
+					.add(pos);
+			double dotProd = faceNormal.dotProduct(beamDir);
+			if (dotProd == 0)
+				continue;
+
+			double newLambda = (faceNormal.dotProduct(posOnSide) - faceNormal.dotProduct(get(0)
+					.getStart())) / dotProd;
+			Vector3d offset = get(0).getStart()
+					.add(beamDir.scale(newLambda))
+					.subtract(posOnSide);
+			if (newLambda < lambda && (Math.abs(offset.x) < .5 && Math.abs(offset.y) < .5 && Math.abs(offset.z) < .5)) {
+				lambda = newLambda;
+				minDir = testDir;
+			}
+
+		}
+		return minDir;
+	}
 }

src/main/java/com/simibubi/create/content/optics/aligner/AlignerBehaviour.java

@@ -82,8 +82,12 @@ public class AlignerBehaviour extends AbstractLightHandlingBehaviour<AlignerTile
 
 	@Override
 	public Stream<Beam> constructSubBeams(Beam beam) {
+		if (beam == collectedBeam)
+			return Stream.empty();
 		Vector3d beamDir = beam.getDirection();
-		if (!beam.isRemoved() && beamDir != null && AngleHelper.deg(Math.cos(beamDir.dotProduct(getFacingVec()))) < 60) {
+		if (!beam.isRemoved() && beamDir != null && AngleHelper.deg(Math.cos(beamDir.dotProduct(getFacingVec()))) < 60
+				&& getFacing().getOpposite()
+				.equals(beam.getBlockEnterFace(getBlockPos()))) {
 			beams.add(beam);
 			requestBeamUpdate();
 		}