Curving a background image around an object

[Ofnuts]

Time for some more detail. Assume you want a background made from this:

   

Filters > Map > Map object to Cylinder will wrap the whole image around a cylinder, like the label on a bottle. The center of the image will be in in front of you, and the left and right edges of your image will be joined together on the back of the bottle. But what you want is the other shape, what you would see through the bottle on the back of the label, and you don't want th elabel to be fully wrapped either. So:

• You flip you image horizontally
  
• You add transparent areas on the sides
  
• While you are at it, add an empty transparent layer and move it to the bottom of the stack (and then make sure that you re-select the background image)
  

So you should have something like this:

   

(note that the dome shaped monument to the right of the Eiffel tower has moved to the left.

You can then call Map object. The settings:

   

Options:

• Of course you want Map to cylinder
  
• Make sure that the "Show wireframe" and "Update preview live" are set
  
• It can be useful to make it Create a new image (because you are going to try many times)
  

Light:

• You likely want mostly directional light. The direction vector should be adjusted so that the light is the same direction on the background  and on whatever you will put in front. With the shown settings, light is from top left, a little behind the viewer
  
• Light color can be adjusted too, maybe you want a bit of yellow.
  

Material:

• Intensity: Ambient doesn't create shadows, Diffuse does, so you want the adequate mix (possibly adjusted to look like your added subject)
  
• Reflectivity: Mostly use Diffuse, because the other two are going to make you background made of plastic (or use them sparingly)
  
  

Orientation:

• When working in that tab, keep in mind that the preview is lying. It is square but your image is not so the image in the preview is compressed laterally...
  
• Position: the Z cursor move the cylinder close or father from the viewer
  
• Rotation: the all important 180° around Y (because you are looking from the back of the label
  

Cylinder:

• Set the top and bottom cap faces to the empty layer you added at the beginning.
  
• You probably want to reduce the radius
  

Then hit OK, check the results, and start again (Ctrl-Z, and Filters ➤ Re-show "Map Object", because you rarely get it right the first time. It is important to be very systematic and note down the settings you used in previous attempts so that you can change one setting after the other and hone in on your ideal result. Then, eventually:

   

(where Bonaparte's tomb is back to the right of the Eiffel tower)