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Combining 3D and 2D Images

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In this article, Janet Ashford and John Odam show you how to combine a rendered 3D image with the scan of a photograph.
This article is adapted from Start with a Scan by Janet Ashford and John Odam.
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Another way to create interesting 3D images is to use an image-editing program to combine a rendered 3D image with a scan of a photograph. Architects often use this technique to create an artist's rendering to show a client how a proposed building will look. They scan a photo of the building site, render an image from their 3D model of the new building, then meld the two images together in Photoshop or a similar program. One key to a realistic result is to make sure the lighting in the model is similar to the lighting in the photograph in intensity, color and direction. That way the shadows on the model will fall in the same way as the shadows in the photo. In addition, when combining the two images it's often necessary to carefully select and remove whatever unwanted objects may be in the original photo, select and insert the image of the new object, then blend it into the photo by cloning areas of the surrounding landscape, sky or other elements. This kind of combining of images can be done not only to create realistic images that fool the eye, but to create fanciful or surrealistic images by placing images of unlikely 3D objects, perhaps at an improbable size, into a photo of a landscape or a cityscape. Applying a filter to the final, combined image will help to meld the photo and 3D elements together.

Scanning a photo, rendering an image

We started with a photo of rowboats at a small dock (A) and a rendering of a sailboat from Ray Dream's Dream Models. The sailboat was modified to include a red hull and the camera was positioned to capture a view similar to the position of the rowboats in the photo. The directional lighting was set up to imitate the lighting in the photo, which was taken with the sun to the left, at about 9 o'clock in the morning (B). The sailboat was rendered with a solid background so that it would be easy to select and copy it by selecting the background with the wand tool and inverting the selection to select the boat.

Combining two images

Using Photoshop, we selected a rowboat and deleted it (C). Then we selected the sailboat and pasted it into the photo in a separate layer (D). We deleted the rudders and used the clone tool to fill the white gaps around the sailboat with sampled textures from the photo. To create realistic highlights on the hull of the sailboat, we selected and copied the lower part of the original rowboat's hull and pasted it into the new file, stretching it to fit over the bottom half of the sailboat's hull in Darken Only mode. We also decreased the color saturation of the sailboat to make it fit better with the saturation level of its new surroundings (E).

Filtering the image

The finished, combined image looks fairly realistic, but to make the photo and new sailboat fit together even more seamlessly, we experimented with applying three different Photoshop filters to the image: Colored Pencil (F), Graphic Pen (G) and Watercolor (H).


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