The problem with rotating a normal map in photoshop is that it’s unaware of the direction of the vectors or RGB channels. Rotating a normal map by 180° in any image processor will be equivalent to negative normal strength – things that are supposed to stick out will be caved in and vice-versa.
After a few days of trying to find a tool to rotate a normal map I put together my own.
Using three.js we can apply the original normal map on a plane, rotate the plane, render the plane with Normal material texture, and the result takes into account the normal map rotation.
Try it for yourselfOpen Normal Map Rotation Tool
- Flip Horizontal and Vertical
- Normal Map Strength
- …let me know!