This entity lets you place special textures called decals in your map, on top of solid brushes. Things like scorch marks, cracks, oil, lettering, etc. can be applied.
The Decal Tool in Hammer or J.A.C.K. is an easier way to apply them.
Attributes
Name (targetname) - Property used to identify entities. Setting a name will hide the decal by default and it will need to be triggered to be drawn.
Pitch Yaw Roll (angles) - Sets the pitch (up / down), yaw (left / right) and roll (bank) respectively. The compass in WorldCraft / Hammer corresponds to Yaw. The settings are not always (or not all) used.
texture (texture) - This defines which image from decals.wad will be displayed by the entity.
Flags
Not in Deathmatch (2048)
Notes
Works only with decals.wad textures.
Works only on singleplayer mode. [verify?]
Applies only to world brushes and brush entitieswithout an origin brush (in other words, brush entities whose origin is at 0 0 0).
If given a name, it will start hidden. Triggering it the first time applies it. Triggering it again however will not cause it to disappear.
angles has no function on this entity. Instead, the decal is oriented and scaled according to Rotation, Scale and Align of the face of the solid it is on.
If the decal appears mirrored, simply put the face texture's alignment to Face, or negate the X scale while aligned to World.
Doesn't count on the texture memory usage of the map, but each entity counts towards the entity limit at runtime.
Can be placed at a maximum distance of 3 units from the face of a solid and will stick on any face within that range – say you place it in the very corner, then it will be rendered both on the walls and floor or ceiling.
Doesn't work on brush entities that are in SolidRender Mode. In fact such brush entities don't display any decals.
Hammer Editor: managing this entity can be a bit buggy. Use Ctrl+M and hit Enter to update the texture and sizing.
Decals scaling relative to the scale of the texture of the face it's applied to works in weird ways (tested on 25th Anniversary branch):
If the X and Y scales are identical, the decal will always be at 1.0 scale in both axes.
If the X scale is 1 and Y is ≠ 1, the decal will stretch along the Y axis.
If the X scale is ≠ 1, the decal will scale in both axes inversely to X's scale. So if X=2.0 and Y=1.0 then the decal will be at 0.5x scale relative to the face ergo [1.0 0.5]. Note how this squishes the decal along the Y axis.
If the texture is rotated or skewed, the decal will rotate and skew along.
Tip: you can form different symbols by superimposing decals or placing them close to each other. Changing the face properties of the solid the decals are on will change how they will be rendered as well.