... for those who won't get the explanation out of the files in the previous sent ZIP-file...
1) I made a simple shop window in SketchUp (SU) everything in 1 layer. (You also can use seperate layers for each part.)
2) All parts (ie. frame, glass and the sticker placeholder) are seperate groups
. I put the placeholder 5mm in front of the glass
3) For all the parts (except for the sticker placeholder) I assigned a material.
4) The sticker part...
5) In Photoshop I made a "design" which has the same proportions
as the placeholder in SU (in this case; placeholder is 2000x2000mm, the photoshop design is 1000x1000 pixels)
6) I saved the design as a PNG-24 file (which holds on to the transparency). In Photoshop you can find in the FILE dropdown a command called "Save For Web & Devices". From there you choose the PNG-24 option.
7) Went back to SU and opened the sticker placeholder group.
Went to File and choose "Import...", found the PNG file, marked "Use as texture
" at the bottom right and clicked on "Open".
9) Now I "glued" the sticker on the placeholder and closed the group.
10) I exported the model to FBX with the FBX export options; a) Geometry (triangulate all faces, export two-sided faces), b) Materials (Export texture maps
), c) Scale (Swap YZ coordinates, Units: Centimeters)
11) Opened Lumion and imported the FBX file.
12) Assigned the materials for the frame and glass.
13) Now the sticker part doesn't have the sticker yet but the UV coordinates are there.
14) Assigned a STANDARD
material to the sticker part and clicked on the textures icon. clicked on the left (black) square and found the PNG file and clicked on Open.
15) Now the sticker is applied but no transperancy yet. For that I used the "Reflection or clip"-slider (at the bottom-right in the Properties section) and moved it all to the right.
16) DONE!!! I also played around with the other settings like reflection etc. until I was satisfied.
In short; the place holder in the modeler (in this case SketchUp) is the key for assigning a sticker in that modeler just to ensure the UV-coordinates. In Lumion you just have to re-assign the texture. I hope sincerely though that the guys at Lumion will find some day an easier way to put stickers on any face without using place holders in the modeler.