Why is only half of the object covered when I apply decal?
Accepted answer
OK first of all you made your Vase far to complicated.
Secondly your image was on the centre plane to use it as a decal you have to put planes on the right and left side of your model then new sketch with image then decal both to nearest surface.
Decal rarely covers 100% of the model its better to use your image as a texture
https://www.youtube.com/watch?v=B4tPD6tYQco
1 Other answer
You need to wrap the decal, have a look at this screencast that I recorded: https://autode.sk/3ffwTn2
