I want to create multi texture shader and i need to create a custom mask (spline mask) so i can mix foreground texture with the background texture where i can pipe that spline mask into the mix input of the mixRGB node. But i can't find any mask related node in the shader editor . Am i not allowed to add mask in shader editor (just like in compositor) ? i want to draw my custom mask without using photoshop etc. Any idea ? Do i have to render the alpha channel from the compositor first ?