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Classic FPS Games Perpsective

Started by September 01, 2013 10:57 AM
4 comments, last by ill 11 years, 4 months ago

Hey there!

My question is how perspective in Doom or Wolf drives those games?

I'm interested in that classic FPS perspective theory.

Some things are strangely foreshortened and that's good effect that I'd like to achieve in my productions.

Any tutorials containing topic of FPS games creation are also much appreciated smile.png

Are you talking about full 3d or just sprite based shooters like Doom and Wolfenstein?

If it's 3D it's just like any other 3D game. Only difference is you don't render the first person model with the world. You render it after in a separate pass or else the character's guns, arms, legs, etc... will clip through walls.

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I mean sprite based,oldschool as you said :) not full 3d

There's this excellent review: http://fabiensanglard.net/doomIphone/doomClassicRenderer.php

Being that it's from back in the day it's full of a few hax that you can probably avoid nowadays.

what hax?

Well nowadays you can probably just use OpenGL. In fact there are many OpenGL powered source ports of games like Doom, Duke Nukem, etc... They don't have to rely on any tricks for rendering geometry. They just render a bunch of arbitrary polygons and don't even think about perspective or anything. Just set up the camera correctly, etc...

Since you have the zbuffer, you don't need to worry as much about rendering polygons in the correct order. Overdraw isn't too much of a problem either, games overdraw nowadays all the time just fine. There are ways to prevent it a bit, by roughly rendering polygons front to back. That requires some sorting though. Some engines do a depth prepass by rendering the geometry only to the depth buffer with color write off, making the pixel shaders do no complex work. Then rerender the scene again, and this time there's no pixel shader overdraw on solid geometry.

You can still have sprite based FPSes, just draw a flat billboarded rectangle with the sprite instead of a model. In fact there's even a killing floor mod with doom enemies.

Doom did some things, such as making all walls at 90 degree angles with slightly brighter or darker lighting to add contrast. Also the diminished distance lighting, making things darker farther away. Now that's just done with fog.

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