In this example I used 3DS's Sunlight system to good effect. The reason was because the client not only wanted
a photomontage but also wanted a realistic sunlight position too. Once you've input the relevant information into the sunlight parameters box, it acts in
exactly the same way as a normal shadow casting spot. This was set to an illumination of .75 with a medium-high, slightly yellow ambient light. Then I
dotted several other spots and omnis around the scene mostly with attenuation properties on to give the model very localised lighting i.e.- in the atrium,
under the soffit, the main entrance and in some of the shop display fronts. I also added a non-shadow casting omni (illum. set to 0.3) over to the far left
hand side of the scene just to help with the ambient lighting. The curved blue curtain wall on the right hand side was also lit by a spot projecting a
tiled sky map onto it. Now it's test render time. Luckily I didn't have to match up shadow angles with the photgraph this time because I was using the
sunlight system but because I had many lights (about 15 spots and 50 omnis) in the scene, a few low resolution tests had to be done just to get the lighting
levels correct. The only light casting a shadow is the sunlight. Now switch over the low resolution backround with the high resolution one and do your
final render. This was rendered at 2000x1500 pixels, always a 1.333 ratio, and saved as a TIFF file. The above image shows the final render and as in case
study no. 1, i've toned down the backround for clarity.
The first stage in Photoshop is to separate the render (right image), from the photograph (left image). This is
done using the same method as i've mentioned in case study no.1. We now have the rendered image on it's own layer over the original photograph. If you have problems matching up the
rendered image from the image buffer exactly over the original photograph, you can also use IMAGE > APPLY IMAGE (blending normal) into a new layer. Now go
through the EDIT > TRANSFORM options to fine tune the camera matching to fit more or less perfectly.
The first job was to super-impose the backround's trees over the front of the render. The left image shows the
mask I used to do this. This masked area was basically created by colour selecting and marquee'ing. This selection was then 'punched' through the render
layer on top to cut out the gaps for the trees. A very slight softening and feathering was used on the marquee to smooth out the edges.
This same mask was used for the sky. I pasted in a suitable looking sky scanned in from a photograph making
sure the sky layer was over the backround layer but under the render layer in the stack. The mask we previously created was then inverted and used to delete
a perfect edge for my sky (left image). The final stage was to paste in some seagulls and a jumbo jet for extra realism, then colour balance and contrast
all the floating layers to match up with each other and the original backround photograph.
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