I was playing with some scale test with the approach of using particle object, but I have this strange facing problem, any ideas? (I set rotation off and random to 0)
Try selecting all faces and hitting control-N to make sure all the normals are facing the same direction.
If that doesn’t work, then it might be because of the faces are 'rotated 'the wrong way. If they are, then there’s a solution, but it’s pretty tedious.
Go into edit mode and select one of the offending faces, and hit control-T to split it into two triangles. After that, press ‘F’ to merge them into a single face, then tab back out of edit mode to see if it’s facing the right direction.