I want to fill a SKShapeNode with a linear gradient. Being a programming perfectionist I want the solution to be as customizable as possible. So I decided to use a

If you change c1 and c2 to other colors, the bug will stay there.

CodePudding user response：

Like the comments said, the color value you return should already be premultiplied by the fragment's alpha value.

From Apple's documentation - Creating a Custom Fragment Shader:

Typically, the color value you return in this variable should already be premultiplied by the fragment’s alpha value.

You might also want to use v_color_mix.a if you want your shader to take into account the alpha value set on the node:

gl_FragColor = col * v_color_mix.a;