$seamless scale: Difference between revisions

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<code>$seamless_scale</code> is a parameter supported by the [[LightMappedGeneric]] and [[WorldVertexTransition]] [[shaders]]. It is to be used in Valve Material Type ([[VMT]]) files for the Orange Box version of the [[Source Engine]]. It is not supported by any shaders in the Episode 1 version of the Source Engine.
<code>$seamless_scale</code> is a [[material]] command supported by [[LightmappedGeneric]] and [[WorldVertexTransition]] in the [[Orange Box]]. It was created to sidestep texture stretching issues on [[displacement]] surfaces.
This parameter is useful for a material frequently applied to complex displacement surfaces. It removes the unpleasant material-stretching effect.


== Basic syntax ==
== Basic syntax ==


<code>$seamless_scale <float></code>
$seamless_scale <float>
Example:
 
  "LightMappedGeneric"
  LightMappedGeneric
  {
  {
  "[[$basetexture]]" "Example\Example01"
  [[$basetexture]] Example\Example01
  "[[$surfaceprop]]" "concrete"
  [[$surfaceprop]] concrete
  "$seamless_scale" "0.005"
  '''$seamless_scale 0.005'''
  }
  }


== Functionality ==
== Caveats ==
 
; Known Problems
 
: '''A:''' Materials with this parameter cannot be scaled in the [[Hammer Face Edit Dialog]]. They must have the float value changed in their VMT.
: '''B:''' The 3D window in Hammer may display graphical glitches if a material of this sort is applied to a face.
: '''C:''' Certain "treatment" mapping techniques either will not function or will create strange lighting artefacts when used with <code>$seamless_scale</code>. These parameters will have to be removed until <code>$seamless_scale</code> is not in use anymore.
 
<div style="padding:3px 3px 3px 15px;margin:2px;">[[Image:note.png]]&nbsp;'''Note:''' You can negate the functionality a parameter, without removing it outright, by putting two forward slashes (//) before the parameter in the VMT.</div>
 
; Non-functional Treatment Mapping techniques
 
: Normal Mapping
: Detail Mapping
 
; Functional Treatment Mapping techniques
 
: Specular Mapping
: Specular Mapping utilising Self-Shadowed Bump Maps


Example setup of <code>$seamless_scale</code> with functional Treatment Mapping:
* You can no longer scale the material with the [[Hammer Face Edit Dialog]]. The parameter's value must instead changed in the material itself.
LightMappedGeneric
* Hammer's 3D view doesn't handle the material correctly.
{
* [[$bumpmap|Standard normal mapping]] isn't supported, [[$ssbump|only its self-shadowing cousin]].
"$basetexture" "Example\Example01"
* <code>[[$detail]]</code> textures are unsupported.
"$surfaceprop" "concrete"
"[[$bumpmap]]" "Example\Example01_height-ssbump"
"[[$ssbump]]" 1
"[[$normalmapalphaenvmapmask]]" 1
"[[$envmaptint]]" "[ .2 .2 .2 ]"
"[[$envmap]]" "cubemaps\cubemap_Example01"
"$seamless_scale" "0.005"
}


== History ==
== History ==


According to the [[Episode 2]] commentary, this feature was added in response to difficulties experienced with the creation of the [[Antlion]] Caves section. The complicated topography of the areas exaggerated the previously bearable material-stretching effect. This effect is a result of how the Source Engine usually handles [[displacements]], whereby the [[coordinate]] system of the material is locked to the vertices of a displacement surface.
According to [[Episode Two]]'s developer commentary, this feature was added in response to difficulties experienced with the creation of the [[antlion]] caves section. The complicated topography of the areas exaggerated a previously bearable material-stretching effect.


When a [[vertex]] is translated to a different position, the [[planes]] that are naturally created between this vertex and it's neighbouring vertices change size accordingly. Since the material's coordinates are locked to the vertices of each plane, the material must change size, or [[scale]], to fit across the growing/shrinking planes. The material will scale down to fit across a plane that has shrunk, while scaling up to fit across an enlarged plane. If vertices are translated too much, and in too arbitrary a manner, the resulting planes will be wildly different sizes from their surrounding neighbours. Any material applied to such a displacement surface will inevitably then have segments of itself scaled in ridiculously different proportions. One may be twice the X axis scale as it's neighbour, while half the Y axis scale. This will create an aesthetically unpleasing effect, whereby the material appears to stretch at some parts while scrunching up at others.
This effect is a result of how Source usually handles [[displacements]]: a [[UV map]] is locked to the vertices of a displacement surface, and when a vertex on it is translated the polygons linking it to its neighbours stretch or contract accordingly, carrying the texture with them. This can lead to polygons with squashed textures sitting beside others with stretched and blurred ones; an unpleasant effect.


Without very careful and time consuming attention being paid to the displacement creation, it's hard to avoid this problem in terrain such as caves. Even at that there will still be noticeable stretching. So Valve coded a new feature; <code>$seamless_scale</code>. It separates the material's coordinate system from the vertices of the displacement to which it is applied. Materials can then maintain the same scale across a whole displacement surface, no matter how messy the topography is.
<code>$seamless_scale</code> separates the material's coordinate system from the vertices of the displacement, allowing it to maintain a regular scale across an entire surface without any designer effort.


[[Category:List of Shader Parameters|B]]
[[Category:List of Shader Parameters|S]]
[[Category:VMT Texture Reference]]
[[Category:VMT Texture Reference]]

Revision as of 07:43, 17 September 2008

$seamless_scale is a material command supported by LightmappedGeneric and WorldVertexTransition in the Orange Box. It was created to sidestep texture stretching issues on displacement surfaces.

Basic syntax

$seamless_scale <float>

LightMappedGeneric
{
	$basetexture Example\Example01
	$surfaceprop concrete
	$seamless_scale 0.005
}

Caveats

History

According to Episode Two's developer commentary, this feature was added in response to difficulties experienced with the creation of the antlion caves section. The complicated topography of the areas exaggerated a previously bearable material-stretching effect.

This effect is a result of how Source usually handles displacements: a UV map is locked to the vertices of a displacement surface, and when a vertex on it is translated the polygons linking it to its neighbours stretch or contract accordingly, carrying the texture with them. This can lead to polygons with squashed textures sitting beside others with stretched and blurred ones; an unpleasant effect.

$seamless_scale separates the material's coordinate system from the vertices of the displacement, allowing it to maintain a regular scale across an entire surface without any designer effort.

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