# Decal projection on complex shapes

I'm trying to add decals to stairs. I've set up a image as plane on the $$X$$ axis, and all I want is blender to do is project the image along the $$X$$ axis. However, through all the methods I try it doesn't work. It textures the top of the steps and I end up with a triangle like texture. All I want is to have an image and then along one axis just apply it to the object

• don't you want to do it in the Shader Editor? – moonboots Jan 25 at 14:06
• i not sure what you mean – Axel Hansen Jan 25 at 14:07
• could you please show a picture? – moonboots Jan 25 at 14:22
• Forget about "Decals", as new planes to be added on top of other surfaces. Why is it is such a bad idea adding faces on top of other faces? 3D render engines have a hard time when two co-planar surfaces are parallel and on top of each other, or close together. That will result in a problem called z-figthting, where the render engine cannot distinguish clearly between two or more surfaces and they end up rendered randomly on top of each other. A more efficient way is combining different textures or materials that are part of the same object. – susu Jan 25 at 20:12

## 1 Answer

Get an angle of your object "front on" by using one of the orthographoc angles (Numpad 1 for front, Numpad 3 for side, Numpad 7 for top, or Numpad 9 to flip any angle by 180deg), and then press U (unwrap), and select "Project from view" This will make your UV map resemble a "snapshot" from that angle.

After that, connect your image texture as normal. It comes out looking like this:

If you want to stop the image from appearing on the top and sides of the stairs. you can use the respective axes from the Normal Vector as a mix factor between your image and whatever other material (I used plain white for the example). The Normal vector doesn't like being recombined without a third axes, so you have to do it in 2 stages - one for each respective axis that you need "erased":

• this is almost the result im trying to get, however its wrapping around the stairs on the side, and i couldnt understand how to replicate this, im trying to put the image on only the front part of the stairs – Axel Hansen Jan 25 at 14:46
• Does the object have to have only one material, or are you ok with using more than one? – Christopher Bennett Jan 25 at 14:56
• well the stairs are all supposed to be plastic but the decal doesn't, that why the stair are one object – Axel Hansen Jan 25 at 14:58
• I edited my answer with a possible solution for you. – Christopher Bennett Jan 25 at 15:28
• i already have a specific material for the stairs, and the image i want to add is semi transparent, does this method still work? – Axel Hansen Jan 25 at 15:40