If the resolution above ^ Does not help, then your best bet is to re-do the HM and TM. Ensure both are 513x513 as DoctorFlob said, and also ensure you dont accidently click layers for the Height Map. Make sure the HM is .PNG as well as the TM, and both are saved in; C: > FeralHeart > Media > Terrains. A folder for your map will be automatically created once you first save it in the map maker. That should about do it.