Water (shader)

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Revision as of 10:00, 26 June 2011 by TomEdwards (talk | contribs) (Flow)
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A custom Water material from Resistance And Liberation.
Real-time reflection of entities in Episode Two.

Water is one of the Source engine's most complex shaders. It creates animated, real-time reflective and refractive, fogged, normal-mapped water.

Special behaviour

Expensive and cheap
Water materials fall into two groups: expensive and cheap. Expensive water reflects and refracts the world in real-time, while cheap water uses an $envmap and does not refract. Users can disable expensive Water rendering through their video options, so always place env_cubemaps.
Above and below
Water actually requires two materials: one for above the surface and one for below. These materials are independent of each other, but of course for proper effect need to correlate in most areas.

Shader parameters


Tip.png Tip: There is no $basetexture here. The surface is a combination of fog colour, animated bump map, and reflection.
$abovewater <bool>
Whether this material is used for above or below the water’s surface.
$bottommaterial <material>
Required field. This is the material (not texture) to use when underneath the water’s surface. The bottom material must have $reflecttexture and $abovewater disabled, but can otherwise do whatever it wants.
$underwateroverlay <material> (in all games since <Half-Life 2: Episode Two><Half-Life 2: Episode Two>)
Applies a screen overlay when the camera is underwater. Generally used with effects\water_warp01. Requires $abovewater to be 0.
$bumpmap <texture>
$normalmap <texture>
A Du/dv map for DirectX 8 rendering ($bumpmap), and a bump map for DirectX 9 and above ($normalmap). These should be animated unless the water is to be perfectly still.
Note.png Note: The $normalmap command is unique to the Water shader, and uses a normal map. A du/dv map is used for $bumpmap when using the Water shader. The $dudvmap command is obsolete.
Tip.png Tip: Use $bumptransform with the TextureScroll proxy to move the normal map.
Size/angle of $scroll1 and $scroll2
$scroll1 "[<normal X> <normal Y>]" (in all games since <Half-Life 2: Episode Two><Half-Life 2: Episode Two>)
$scroll2 "[<normal X> <normal Y>]" (in all games since <Half-Life 2: Episode Two><Half-Life 2: Episode Two>)
If $scroll1 is defined and X is not zero, two more instances of the normal map will be drawn in such a way that they are merged together. The first layer is 7x larger and rotated 45°; the second is 2x larger and rotated 90°. The parameters specify the speed and direction that the extra layers will move. (Valve's materials usually contain a third number, but it doesn't have any apparent effect and is most likely obsolete.)
$dudvframe <int>
$bumpframe <int>
Frame to start the animated du/dv map and bump map on, respectively. Somewhat confusingly, $bumpframe affects $normalmap, which should be pointing to a bump map.


$fogcolor <RGB matrix>
This is the color of the water’s volumetric fog. Generally this value should match the color used in the bottom material.
$fogenable <bool>
Enable volumetric fog for the water.
$fogend <float>
This is the distance in inches from the eye at which water fog ends.
$fogstart <float>
This is the distance in inches from the eye at which water fog starts.
Warning.png Warning: This must be 0 for edge fading to work properly.


$envmap <env_cubemap / texture>
Provides reflections for cheap water. See $envmap
$forcecheap <bool>
Make this water cheap regardless of the water_lod_control entity's or user's settings. This will disable real-time reflection and instead use $envmap. Refraction is assumed to be opaquely the water fog color.
$forceexpensive <bool>
This forces the water to render itself as expensive, regardless of the map's water_lod_control or the user's settings.
$reflectamount <float>
This is the amount of warp for the reflection. Higher values produce more visible reflections.
$reflectentities <bool>
Make the water reflect entities. By default, no entities are reflected.
$reflecttexture <texture>
Texture to use for reflection. For real-time reflections, use _rt_WaterReflection.
Tip.png Tip: Specify $refracttexture without $reflecttexture to get real-time refraction on $envmap reflections.
$reflecttint <RGB matrix>
This is the color tint for the real-time reflection and environment map.
$refractamount <float>
This is the amount of warp for the refraction. Higher values produce more warping.
$refracttexture <texture>
Texture to use for refraction. For real-time refractions, use _rt_WaterRefraction.
Tip.png Tip: Specify $refracttexture without $reflecttexture to get real-time refraction on $envmap reflections.
$refracttint <RGB matrix>
This is the color of the refraction.
Warning.png Warning: It is recommended that you set this to white or something close to white so that edge transitions work properly on DX9.


$flowmap (in all games since <Left 4 Dead 2>)
This is a texture that defines flow velocity by skewing and scrolling the $normalmap. For the preservation of sanity Valve generate theirs with an unreleased Houdini plugin.
L4d2 flowmap user.jpg L4d2 flowmap tex.jpg L4d2 flowmap dev.jpg
See a clip of the effect on YouTube. For a detailed description of how it all works see Alex Vlachos' SIGGRAPH 2010 paper.
The size of the normal map in relation to the flow map. Valve often use very high values (e.g. 800). To do: 1 == one normal map repeat for every texel?
To do: No apparent effect.
Confirm:Time needed for one complete scroll of the normal map?
To do
How rough surface of the water is.
How fast the water flows over its specified distance.
A treatment texture used to break up repetition of the normal map.
To do: Has the same effect as $flow_normaluvscale?
Replaces the water surface with a literal rendering of the $flowmap texture.


%compilewater <bool>
This is needed to make a map using the material compile properly.
$surfaceprop water
Tells the physics system that the surface is water. See $surfaceprop.
%tooltexture <texture>
Defines the texture Hammer will display in the material browser.
WaterLOD proxy
This connects the water_lod_control entity in a level to the water’s internal parameters. This must be declared in the material for the LOD mechanisms to work properly.

See also