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Saturday, July 9, 2011

Methods For Creating a 3D Photo-Montage Visualisation

By Daisy Solis


A 3D Photo-Montage is simply a photograph merged seamlessly together with a 3D CGI element. 3D Photo-Montages are particularly used in construction and development, to show what an area will look like once a structure is built or changes to an existing building occur. To produce this image you will need a 3D and photo editing package for your computer. You will also need the proposed plans of the building, a survey of the area and all importantly a photo of the scene.

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.

When your modeling remember that the surrounding elements like the lampposts and eves of houses have to be modeled to the correct scale and level. This saves any complications at the camera matching stage.

When you have modeled the scene, upload the original photograph into a selected 3D Visualisation package as it is to be used as a background and the create a camera. The camera needs to be positioned as close as possible to get a match to the scene. A good tip when your doing this is to draw a spline around the site, making sure it's at the correct level, in the 3D package and hide any elements except the surrounding elements and the spline. To adjust the settings on the virtual camera 35mm is a good lens to start with but if you know the size of the lens that was used to take the photograph then use them settings. You need adjust the virtual camera until everything matches up. the focal length may also need to be adjusted but this is usually if the the camera isn't lining up. When everything looks good and you happy enough unhide the geometry used for the montage and then hide everything else. Lighting the scene comes next, do this as closely as possible to the picture. By studying the direction and height of the sun you can match the virtual lights accordingly.

Once all these stages are complete you need to render the scene with an 'alpha channel' but dont include the photograph as a background. Open the render and photograph in photoshop and layer them up... blend the exposure and cut out any elements in the foreground eg trees etc so the CGI element glues as much as possible to the photograph.




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