VERC: Motion Blur Effect Last edited 2 months ago2019-04-21 12:30:01 UTC by Penguinboy Penguinboy

With the advent of the null texture, it has become possible to create a motion blur effect in Half-Life maps. The key premise of the effect is intentionally creting a Hall of Mirrors (HOM) behind a somewhat transparent entity brush.

For those of you that dont know, a HOM is the effect you get when you noclip around in the void in open GL with gl_clear set to 0 (default). If the engine has nothing to render, then each pixel simply displays the same thing it did in the last frame, resulting in something that looks like this:
User posted image
In order to create this motion blur, you will first need to pick up merl's custom build of ZHLT. The latest version as of 8/1/02 is 1.6.1, which you can get here:

Zoner's Half-Life Tools - Merl's Custom Build

Configure Worldcraft to use the new compile tools, and load up the new zhlt.wad that comes with 1.6.1. Now make yourself a room covered entirely with the null texture. Inside the room, between where the player will be, and the null textured wall, make an entity brush with rendermode texture, renderamount 0 < x < 255. A good number is around 100.

Heres what will happen: the engine will see the func_whatever and render it, but only 100 parts out of 255. For the other 155/255 parts, it will try to render the face directly behind the entity brush, which is null, which means that the face has been stripped off during the compile process, so the engine has nothing to render for it. Therefore, for the other 155/255, it renders the last thing it saw, which is probably part of the func_wall you just looked at thus making motion blur.

Here is what it looks like in-game:
User posted image
HOWEVER, if you are running in software mode, the above scene would only look like this:
User posted image
As you can see, it is imperative to make sure that your room would look at least OK if the motion blur wasnt there, and just have the motion blur as an added visual bonus for ogl gl_clear 0 users.
This article was originally published on the Valve Editing Resource Collective (VERC).
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