Creating Brush Entities

Properly-sized cube with 32x32 texture.

In Hammer, a Primitive is a relatively simple brush object. Primitives can be world geometry or interactive entities subject to physics & damage. In this example, we will create an interactive primitive, subject to physics & damage in the map: specifically, a 32 unit crate.

Select the Block Tool and create a cube in your map.
Open the Texture Browser and filter for dev crate. Dev/dev_measurecrate02 should be a 32x32 crate texture.
Apply the dev/dev_measurecrate02 texture to your cube.
Note: If the grid on your 2D views is too large to get down to 32 units, press the [ key or click the Smaller Grid button to create smaller objects on the grid.
Resize your cube using the Selection Tool until the texture fits properly on the cube.
Note: To this point, creating primitives for world geometry and for interactive objects is the same. In order to specify whether our crate is, indeed, world geometry or an interactive object, we must select it and move it either toWorld or toEntity.

toEntity button (Ctrl+T)
Select the crate using the Selection Tool.

func_breakable object properties

Click the toEntity button to tie a function to the primitive. This will bring up the Object Properties dialog box.
Select func_breakable from the Class: drop-down menu.
Under Keyvalues, select Name and name your crate something descriptive.
Under Keyvalues, select Strength. The Strength value specifies how much damage the crate can take before breaking. Set the value to 1.
Under Keyvalues, select Material Type. The material type specifies the sounds the crate will make and also what type of gibs it will break into. Select Wood from the drop-down menu.
Under Keyvalues, select Physics Impact Damage Scale. This scales damage energy when the object is hit by a physics object.
Note: A value of 0 means this feature is disabled. Set to 1.0 for materials as strong as flesh, smaller numbers indicate stronger materials.
Click Apply and close the Object Properties dialog box.

Crate Texture

Textured functional crate

Once our crate is correctly sized, we can apply a proper texture to it using the same technique we used previously.

Open the Texture Browser and filter for crate.
Select props/woodcrate001a and apply it to your cube. You may have to use the Face Edit Sheet to fit the texture to the cube.
Note: Ensure that the texture is aligned to Face.