Black Edges Around Cutout Textures
Dark halos on leaves, hair and fences
Also known as: Alpha fringing · Dark outline on alpha texture · Black halo foliage texture · Alpha bleeding · Edge bleed
Quick answer
Dark halos around leaves, hair cards and fences happen when the color behind the transparent pixels is black, because filtering and mipmaps blend that black into the visible edge. The fix is to extend the real colors outward past the alpha edge before export, a step called dilation or edge padding, so the blended pixels are leaf-colored instead of black. Do it in your painting tool or in Photoshop before saving.
How to fix it
In Substance Painter, export with dilation enabled so color continues beyond the shape. In Photoshop, expand the artwork beyond the alpha edge or use a plugin that bleeds color outward, and keep the alpha channel separate. In Unreal, check that the material uses the Masked blend mode with a sensible Opacity Mask Clip Value, and look at the edges at the distance where mipmaps take over, since the halo often shows only far away.
Tools that use Black Edges Around Cutout Textures
See also
Texture Padding
Color extended beyond UV island edges
Blend Mode
How a material combines with what is behind it
Mipmap
Pre-filtered texture down-sampling chain
Two Sided Material
Show a surface from both sides
Save Alpha From Photoshop for Games
TGA and PNG with transparency
Alpha Channel
Fourth channel that stores transparency or a mask