Collision Hulls

Created August 2004

Updated 09-20-04

This tutorial will show you how to create a custom size collision hull. Collision hulls are usually added to a map to provide an invisible ramp for a player to walk on while they are walking up/down stairs. With out this collision hull, the players screen will jump up and down.

Creating your custom Collision Hull

You will need to make a custom sized builder brush around your stairs. You will need to know how to clip a brush first. Make the builder brush the same width of your stair. Now you need to make an ramp that touches the edges of the stairs. See the picture below for an example. The red brush is the builder brush, the blue brushes are your stairs.

Before you create the brush, you need to apply a texture to it. Open up the Texture browser, select File, then Open, and look for R6_Common.utx. Select it and press the Open button. Look for the orange texture with the words Collision Hull on it. The name of the textures is Texture Hull [DXT1]. Select that texture, you will see a green box behind it confirming it has been selected.

Now you need to make the builder brush a specific type of brush (collision hull). On the left tools bars, select the Add Special Brush button. A window will appear with a box named Prefabs. From the drop down menu, select Invisible Collision Hull. You will notice that the Invisible box has been checked and the Solidity is now selected as a Semi-Solid. Now select the OK button and move your builder brush away from the stairs.

You will see a dark purplish look brush, this is your collision hull. Rebuild your geometry and go to the 3D view (textured). You should see the ramp you just created with the orange Collision Hull texture on it. You should also see your stairs, mine were made from a floor texture in the Airport texture package.

Now we need to apply a texture to face of the collision hull that the player will actually walk on. This will allow the proper footstep sounds to be heard when the player walks on the collision hull. Please read the Extra Info section for tips and guidelines.

Extra Info

It is my personal belief that all stairs should have collision hulls . This will provide a smooth transition and surface while walking up them. Some believe that it is more realistic not to have them. If you walk up a long stairway with out them, you will notice how unrealistic the jumping up and down of your frame is. There is already frame lag and internet lag (for multi-player games), I don't think we need this to be a distraction too.

Since this is a semi-solid brush, it will not create bsp holes if it isn't snapped to grid. I would always suggest building all brushes to grid at all times. But you will notice in the first picture that the two brushes will intersect. Normally this could cause bsp holes, but not with a semi-solid brush.

The texture you apply to the face of the hull that the player walks on should be the exact same texture as your stairs. This will allow the correct foot step sounds to be heard. You must assign foot step sounds to your mp in order for this to happen. In addition, the sound package must support that foot step sound. See the Sound section for more information. I would keep the rest of the hull textured with the orange Collision Hull texture to let you know what it is. In the 3D view, you can toggle collision hulls on and off by press the P key.

If you are using stairs made out of bsp brushes, they will provide karma collision (blocking the player after he dies). It would be better to turn this collision hull brush into a static mesh. This would reduce rendering time for the engine. Click here to learn how to turn a brush into a static mesh and how to create your own static mesh package.

If you are using a stair way that was turned into a static mesh from the editor, I would keep this a brush and enable it to block karma. Click here to learn how to enable karma on static meshes.

Click here for a sample map.

Written by cwv_Odedge