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'Setting up a background image'----背景匹配

'Setting up a background image' 3!osQ1  


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:(一点透视)

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:(两点透视)

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

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. PVZEB  

Fig 2: The set-up file with guides

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

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 (移动选择区域)

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. (现在照片的水平线处于图片的正中间了)
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. (最后沿着顶部和底部参考线裁剪照片。为了方便之后的参考工作,请记下图片的大小,然后保存文件。)

Fig 5: Cropping the image to size (with image size in bottom corner)

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 (视窗和渲染设置)
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.  

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 4