Step 4.2: Depth Pass
Press the Add ... button again and this time choose Z-Depth (Fig.40).
The Z-Depth pass produces an image where the geometry close to the camera is displayed in white while geometry further away gets darker and darker until it reaches a cut-off point and everything behind it is rendered as black
Under Z-Depth Element Parameters you need to set a cut-off point for where the image goes entirely white or entirely black. In the example scene a Z Min value of 0 and a Z Max value of 2000 works out quite nice as the city plane is 2000 units wide and the camera is looking at the city from one end of the plane (Fig.42).
This might need some tweaking though, so I suggest doing a couple of test renders of still frames before rendering the final sequence.
Step 4.3: Matte
Press the Add ... button for the third time and this time choose Matte (Fig.43).
A matte lets you isolate an object in a scene by making the desired object appear as white while everything else is black. In this case we wish to separate the city from the sky and therefore wish the whole city to appear white against a black background. The quickest way to do this is to by going to the Matte Texture Element options and enabling Material ID, setting it to 0. All textures in 3ds Max have their Material ID set to zero by default and hence every textured object in the scene (should be all objects) will appear white on the render (Fig.44).
Finally, check and double-check your settings and have that cup of coffee while waiting for the render to finish (Fig.45).
This is it for Part 1. I'm a beginner at writing tutorials, but hope it wasn't too long and painful. Anyway, this should keep your computer nice and busy for a while, depending on your system. If you want to take a peek at my finished file, you can download it below.
Click to Download Tutorial 3DS Max File 42 kb
to go to Part 2