Transforming sprites — e.g. by rotation or scaling — in your game leads to ugly artifacts on the sprite's borders. The reason for this is that OpenGL has to keep pixels on the border of a sprite crisp.
To get smooth edges you simply have to add 1 pixel of transparency around the sprite.
You can see the difference between a tightly cropped sprite and a sprite with added transparency in the example on the left side.
Adding some transparency gives you a smoother sprite edge.
TexturePacker 3 introduced inner padding — that extends a sprite with additional space. But it also came with some disadvantages:
- It increases a sprite's size
- Transparency was added to all sides of the sprite
- Unexpected results when combined with trim & extrude
With TexturePacker 4 we are now introducing trim margin that replaces inner padding. The new option can be found under Sprite / advanced.
The margin does not extend a sprite but keeps a sprite's transparency when trim or crop is enabled. E.g. if you specify a trim margin of 5 TexturePacker ensures that it keeps 5 pixels of transparency around the sprite when available on the source image.
The result is that you have more control over your sprites: Using your graphics software you can
- add transparency where needed
- keep tiled sprites cropped tight
Btw. trim margin also works with the upcoming polygon mesh sprites in TexturePacker 4.