Setting up a camera to match a photograph in 3D space can be a daunting
task for anyone if you don’t know how to go about it correctly. In this
tutorial I will demonstrate a real simple way of matching a camera in
3D studio max to a photograph background for easy compositing.
Before going in to the tutorial I am going to assume to know the basics of Photoshop 3D Studio Max and Perspectives
One vanishing point:
One
vanishing point is seen in roads rail tracks and any objects that are
made up of lines either directly parallel with the viewer's line of
sleepers)
Two-Point Perspective:
Two-point
perspective can be used to draw the same objects as one-point
perspective, rotated. One point represents one set of parallel lines,
the other point represents the other set. Looking at a box from a
corner, one wall would head towards one vanishing point, the other wall
would head towards the opposite vanishing point.
Three-point perspective:
Three-point
perspective is usually used for buildings seen from above (or below).
In addition to the two vanishing points from before, one for each wall,
there is now one for how those walls recede into the ground. This third
vanishing point will be below the ground. Looking up at a tall building
is another common example of the third vanishing point. This time the
third vanishing point is high in space.
Part 1: Preparing the Background image in Photoshop:
For
this tutorial I am going to demonstrate the process on a simple 1 point
perspective image so that it is easier for first timers to follow but
generally the rules apply to all forms of perspective.
Fig 1: The background image used
Fig. 1
First
of all create a new file in Photoshop, the size isn’t too important (I
have a 2000x2000 template that I use whenever I need to).
Then create 3 horizontal guide lines (top, dead centre, and bottom),
and Shift drag your background image into the Photoshop file so that it
sits dead centre.
Fig 2: The set-up file with guides
Fig. 2
Drag your top and bottom guide lines so that they snap to the top and bottom of your image (as shows in fig 3a & b).
Fig 3a & b: Adjusting the guides and image
Fig. 3a
Fig. 3b
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Now
you need to shift and drag your back ground image up or down so that
the horizon/eye level runs along the centre guide line.
Readjust the top and bottom guidelines so that they are once again snap to the top and bottom of the background image.
Using the select tool select the region between the top and middle
guide (note if you needed to move your image down you would need to
select the region between the middle and bottom guides) and move the
selection (select > transform selection] to the opposite side of the middle guide.
Fig 4: Transforming the selection
Once again adjust the top or bottom guide to snap to the edge of the selection that is furthest away from the middle guide.
The Photo now has the horizon/eye level set right in the middle of the image.
Finally all that is left to do in Photoshop is to crop the whole image
to the top and bottom guides and the edges of the photo. It is also
worthwhile typing in the image dimensions somewhere on the image for
later reference. And save the file.
Fig 5: Cropping the image to size (with image size in bottom corner)
Fig. 5
Part 2: setting up the scene :
Now comes the straight forward bit, open up a new scene and create a “Target Camera” and position it at 0,0,0 so that it is dead centre of the 3D space
Open up the viewport configuration window (Alt+B) and set the “Background Source File” to your newly saved image and use the settings shown.
Fig 6-7: Viewport and render settings
Fig. 6
Fig. 7
Open the render settings window (F10) and set the output size of the
render to the same size as your background image (remember you typed
the image dimensions on to your image for reference). And select “Show safe frame” from the viewport drop down menu.
Fig. 8
And that’s it your background image and scene is all set so that the
camera is the same height as the camera was when the photo was taken
and is now ready for use, simply import your model/models into the
scene and move into position
You don’t need to move/adjust the camera, as that is set up as already.
The only things you may need to adjust is the vertical positioning of
the cameras target (for cases where you have a 3 point perspective) or
the positioning of the model itself into the correct place. Fig
9-11: a simple box in the 3d max scene rendered with a matte shadow
plane underneath, any object/scene can be easily imported in and will
be aligned to the background
Fig.9
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Fig. 10
Fig. 11
نوشته شده
در دوشنبه یکم بهمن 1386 ساعت 2:22 توسط cracker
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