Generating a 3D Photo-Montage Visualisation

A 3D Photo-Montage is a photograph merged together with a 3D CGI components that combine together seamlessly. 3D Photo-Montages are usually created to show the finished result of a building or development under construction or even before building has started. To be able to create such a montage you will need a 3D software package for your computer (3DS Max or Cinema 4D) and you will need a photo editing packages such as Photoshop. The plans for the submitted building, survey of the area for ground levels and of course a photograph of the scene as it is.

Before beginning you need to examine the photograph and consider which elements need modelled and which don’t, anything which isn’t directly visible in the scene can be left out (or modelled with minimum detail), but when considering this you need to also think about reflections in glass etc. and whether the parts not visible to camera will actually be mirrored on reflective surfaces and whether it is worth modelling detail into them or not.

When you begin the modelling stage it is important to work to a scale of 1:1 so the lighting reacts to the scene as realistically as possible. Import all views of the structure into the 3D package and set these to scale. The method I use is to create a parametric box and give it a length corresponding to a large distance in the scene for example the length of the whole building and then scale the corresponding elevation view to match.

During the modelling stage remember to crudely model surrounding elements like lampposts or house eves at the correct scale and level – these will make the camera matching stage much less frustrating.

After you have modeled the scene you now have to import the photograph into a 3D Visualisation package. The picture is used as the background and you will need to create a virtual camera. The camera should be positioned as close as possible to ensure it matches the scene. A great tip to make sure you do this right, is to draw a spline around the site (correct level) in the 3D package and hide any elements apart from the surrounding ones and the spline. To adjust the settings of the virtual camera use the lens that was used to take the original photo, but if you don’t know them starting at 35mm is good. Adjusting the camera to make sure everything lines up may not always work and you might have to adjust the focal length setting but this will not always be the case. When everything looks positioned correctly you need to unhide all of the geometry that was needed for the montage but then hide everything else. Study the height and direction of the sun before lighting the scene. Match the direction to the virtual lights.

When finishing these stages of the process you ill have to render the scene with ‘alpha channel’, do not include the photo as a background. Open both the render and the photograph with Photoshop and then layer them. Then blend the exposure and get rid of any elements in the foreground. This will make sure the CGI will hold as much as possible to the photograph.

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