Decals

Decals are materials projected onto existing surfaces. They can be placed by the level designer, and are also generated by the engine for bullet impacts, blood, and other effects.
Decals are "sprayed" from a location and mark every surface in their path. For instance, a decal applied downward onto a staircase would cascade down onto the top (but not front) of each step.
== Using ==
=== Hammer ===
; 
: Creates infodecal entities, which decal brushes and displacements.
; info_projecteddecal
: An entity that decals models or displacements (but not brushes). The angle of projection can be set, allowing for distortion.
; 
: Overlays are manipulatable decals on brushes and displacements that offer level designers more control.
infodecal and info_projecteddecal create edicts that last until the decal is sprayed (for unnamed decals, this is a split second after the map spawns). info_overlay only creates edicts if named.
=== C++ ===
==== Standard ====
Created in response to impacts, blood, and so on. Limited in number by the value of r_decals, unreliable when transmitted, and not transmitted to players who connect after creation.
; CBaseEntity::DecalTrace(trace_t* pTrace, const char* decalName)
: Shared code. The trace defines where the decal is projected from and its location. 
; C_BaseEntity::AddDecal( <lots of args> );
: Client function where the decal is actually created. In most cases you are better off just calling DecalTrace().
==== Static ====
Normally created by the level designer. These decals last forever and are always transmitted, including to players who connect later on. Any material can be used.
; engine->StaticDecal( Vector localOrigin, int decalIndex, int entityIndex, int modelIndex, bool lowpriority )
: Server only. This system does not appear use entities.
:; Vector localOrigin
:: Where the decal will be created, relative to the target's origin.
:; int decalIndex
:: A value received from UTIL_PrecacheDecal(). Don't use GetDecalIndexForName().
:; int entityIndex
:; int modelIndex
:: Information about the target entity.
:; bool lowpriority
:: Low priority decals are not saved/restored, and can be "re-used on the client preferentially".
; UTIL_PrecacheDecal(const char *filename, bool preload)
: Returns a decal index for use with StaticDecal(). If this is in precache(), remember that it may be called statically; store the result in a global var.
== Creating ==
: This section assumes that you understand the basics of material creation.
Any material can be used as a decal. They generally have an alpha channel however, and can use some special parameters and/or the DecalModulate shader.
decal04.jpg|Source RGB color channels
decal05.jpg|Source alpha channel
Decal06.jpg|Decal in the world
===Material parameters===
; $decal <bool>
: Prevents decal texture clipping.
: 
; $decalscale <float>
: Same as a brush face's texture scale value: the number of units that each texel covers. Normally 0.25 or lower. 
; $modelmaterial <material>
: A separate VertexLitGeneric material to that will replace this one if the decal hits a model.
; $decalfadeduration <float>
: Amount of time to spend fading out. Requires $vertexcolor.
; $decalfadetime <float>
: Delay before fadeout begins.
; $decalsecondpass <bool>
: ALWAYS render this decal on top of decals without this parameter. If two decals with this parameter intersect, they will treat each other how two without the parameter would.
; $fogscale <float>
: Scales the amount of fog affecting the decal. Useful for making important decals stand out in foggy levels.
; $splatter <bool>
: 
Decals do not support normal maps in all engine branches prior to CS:GO. The underlying brushes/displacements must have bumped lightmaps for the decal's normal map to have any effect.
: 
=== DecalModulate ===
For decals intended to mimic the look of pock marks or dents in a surface, the DecalModulate (a.k.a. mod2x) shader is especially suitable: it lightens destination pixels for every source pixel that is over mid-range gray (128) and darkens any destination pixels for every source pixel that is below mid-range gray. This effect can be used to give the impression of depth when applied to a surface.
To begin, create a source image whose color channel will be used for the modulation's source values. Again, light values will lighten pixels they're drawn over, while dark values will darken the destination pixels. Mid-gray values will be treated as translucent.
Next, create an alpha channel that defines a mask for the decal. Because modulation cannot have an exact middle value with DXTn compression, the mask is necessary to prevent "bordering" from occurring around the decal. You can avoid "bordering" without creating an alpha channel simply by using BGR888 format instead of DXT1/DXT5 when you create your VTF, at the cost of being triple the file size.
decal01.jpg|Source RGB color channels
decal02.jpg|Source alpha channel
Decal03.jpg|Decal in the world
Finally, you must create a material that uses the DecalModulate shader. Neither $translucent nor $decal are needed this time.
== See also ==
* Decals in Photoshop
* Decals in GIMP
* infodecal
* info_projecteddecal
* info_overlay
* $nodecal
Category:Material System
Category:Glossary