View source for $lightwarptexture

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[[File:Lightwarp snow.jpg|thumb|200px|The technique was first used in {{dods|2}}'s snow maps, such as Kalt.]]
[[File:Lightwarp heavy.png|thumb|150px|{{code|$lightwarptexture}} is a cornerstone of {{tf2|2}}'s illustrative character rendering.]]
[[File:Lightwarp BW.png|thumb|150px|Posterized color can be achieved, but lighting must be tightly controlled.]]

{{this is a|shader parameter|name=$lightwarptexture|shader=VertexLitGeneric|since=Source 2006|notitlechange=1|nocat=1|dx=dx95}} It tints [[texel]]s depending on their brightness. It can be thought of as localized [[color correction]].

{{Note|Also available for [[LightmappedGeneric]], [[WorldVertexTransition]], [[EyeRefract]].}}

== Caveats ==
{{Important|Make sure the texture is clamped in the VTF otherwise it will render incorrectly. Use '''Clamp S''' and '''Clamp T''' [[Texture flags|image flags]] for that.}}
{{Important|{{code|$lightwarptexture}} on {{Ent|VertexLitGeneric}} requires a {{Ent|$bumpmap}}. If not specified, a default one will be used instead! '''It will be as if a {{Ent|$bumpmap}} is in the VMT!'''
{{Warning| This means that all parameters that don't work with {{Ent|$bumpmap}} also won't work with {{code|$lightwarptexture}}.
* [[$detail#Parameters and Effects|$detailblendmode]] 5-9 won't work - 5 & 6 will work when {{Ent|$phong}} is used.
* {{Ent|$envmapmask}} won't work, except in {{mapbase|2}}.
* {{Ent|$selfillum_envmapmask_alpha}} doesn't work in any branch.
* [[Per-vertex lighting]] won't work prior to {{csgobranch|2}}
}} }}
{{Note|Does not work without {{Ent|$phong}} on {{Ent|VertexLitGeneric}} in {{src13|2}} '''and''' {{csgobranch|2}}.{{workaround|Use {{cmd|$phongboost|0}}.}}}}
{{Note|{{code|$lightwarptexture}} does not seem to exist at all for {{Ent|LightmappedGeneric}} in {{csgobranch|2}}.}}

{{Bug|Does not work when using {{Ent|$detail}} '''or''' {{Ent|$bumpmap2}} on both {{Ent|LightmappedGeneric}} and {{Ent|WorldVertexTransition}}.}}
{{Bug|Does not work when using [[Glowing_Textures#.24selfillum|$selfillumfresnel]] without also using {{Ent|$phong}}.}}
{{Bug|Does not work when using {{Ent|$seamless_scale}}.}}

== Lightwarp textures ==
A lightwarp texture is a one-dimensional strip of pixels. Dark texels will be tinted with the colour on the left-hand side, and bright texels with the colour on the right. 50% gray means no tint. 
{{note|Lightwarp works slightly differently on lightmapped brushes and displacements compared to vertex-lit models. A completely 50% grey {{code|$lightwarptexture}} on a brush or displacement will appear as if lightwarp were not present, whereas the same {{code|$lightwarptexture}} on a model with no [[$phong|phong]] would result in the model being lit uniformly (like GoldSrc flatshade texture mode.}}

=== VTF parameters === 
A lightwarp texture should use uncompressed BGR888 format to avoid undesired color banding on lighting gradients{{ref|1}}, and should be UV clamped.

If using {{vtex|4}}, use these compile parameters:
<pre>
nocompress 1 // disable texture compression, to prevent undesired color banding
nomip 1 // disable mipmaps, which are unnecessary in this instance
nolod 1 // always use the full resolution version of this texture (due to being low-resolution to begin with)
clamps 1 // prevent tints at lighting extremes from blending together
clampt 1 // optional?
stripalphachannel 1 // remove unnecessary alpha channel, if present
</pre>

=== Examples ===
; {{file|ground/snow_warp|vtf}} ({{dods}}):[[File:Warptexture.jpg|border|dod\materials\ground\snow_warp]]
: This is the lightwarp texture used in the {{dods|2}} screen above. It is designed to add a subtle bluish tint to darker snow without affecting brighter regions.
; {{file|models/player/pyro/pyro_lightwarp|vtf}} ({{tf2}}):[[File:Pyro lightwarp.png|border|tf\materials\models\player\pyro\pyro_lightwarp]]
: This is applied to all {{tf2|2}} characters, not just the Pyro. It creates the high-contrast shadows with red-tinged terminators typical of the illustrative art the game apes.
; Posterized (custom): [[File:Warp bw.png|border|Custom texture]]
: This custom warp texture creates a posterized "line art" style. Enabling lightwarp alone isn't enough however: ambient lighting must be at 0 to make unlit areas black, and world lighting must become viewer-dependent to ensure that shadows are always cast.
; Cel Shading (custom):[[File:Cel_lightwarp.png|border|Custom texture]]
:Cel shading can make objects look more cartoony by replacing the smooth lighting gradient with sharp steps.
; Fake $phongdisablehalflambert (custom): [[file:Phongdisablehalflambert warp.png|border|custom texture]]
:Simulates {{cmd|$phongdisablehalflambert}} in games without that command.

Other possible uses of {{code|$lightwarptexture}} include contrast enhancement, tweaking vertex lighting shadow transitions, highlight softening, and more.


::[[File:Celshadingpreview.png|thumb|320px|left|Cel shading in action.]]
{{clr}}

== References ==
<ol>
<li>[https://gamebanana.com/mods/466641 Lightwarp Fixes <nowiki>[Team Fortress 2] [Mods]</nowiki> on GameBanana]
</ol>

[[Category:Shader parameters|l]]