View source for Hotspot texturing

'''Hotspot texturing''' is a method to quickly apply textures to geometry by matching faces to predefined rectangles. This method is especially useful with texture maps consisting of trims and panels, and will allow you to automate a lot of the texture aligning process.

[[File:hotspot_example.jpg|thumb|Example of a structure made with a hotspot texture]]

Valve used hotspot texturing extensively in the creation of Half: Life Alyx to create modular geometry with bevelled edges. This feature has now been brought over to Source 1, inspired by the Source 2 implementation.

This feature is only available in {{hammer++|4}} and {{strata hammer|4}}.

{{todo|Merge the [[Half-Life:_Alyx_Workshop_Tools/Level_Design/Hotspot_Texturing|Source 2 version of this page]] as a separate tab}}

== Benefits ==

* '''Easy to author''': The rectangles in the texture can be created in a consistent and seamless style.
* '''Improved performance''': Since all the rectangles use the same material, they will only consume one draw call rather than multiple like with traditional textures.
* '''Saves file size and VRAM''': Don't need multiple textures, it can be packed into one texture instead.
* '''Quick to apply''': You can just select all faces and press Fit, and the result will be nearly perfect.

== Authoring ==

1. Create a texture with rectangular regions. The rectangles can be any size, as long as they are axis aligned.

2. Create a <code>.rect</code> file. This is a plaintext file containing the list of rectangles. Place the .rect file beside your [[vmt]]/[[vtf]].

Example file that has two rectangles. The origin (0, 0) is from the top left of the texture.
<syntaxhighlight lang=js>
Rectangles
{
	rectangle
	{
		min		"0 0"
		max		"512 32"
	}
	rectangle
	{
		min		"512 0"
		max		"768 32"
	}
}
</syntaxhighlight>

{{note|A UI editor for this is planned, for now measure these rectangles in your image editor of choice}}

3. Specify the path to your <code>.rect</code> file in your [[vmt]] as <code>%rectanglemap</code>. The rect file is assumed to be in the <code>materials</code> folder.

Example:

<syntaxhighlight lang=js>
LightmappedGeneric
{
	$basetexture  hotspot/hotspot_test
	%rectanglemap hotspot/hotspot_test
	$surfaceprop  metal
	$alphatest    1
}
</syntaxhighlight>

=== Example ===

This is an example grate texture with hotspotting.

[https://github.com/ficool2/misc_tools/releases/download/v1/hotspot_example.zip Download]

== Usage ==

With a hotspot-ready texture in Hammer, apply the texture and then press the Fit button. Hammer will automatically read the rect file and apply the hotspotting.

Hammer will try choose the closest matching rectangle within a margin of error. If there is multiple matches for a rectangle, a random one is chosen. Pressing Fit will generate a new random result in this case.

== See also ==
[https://www.defaultinteractive.co.uk/post/hotspot-texturing More detailed article on hotspot texturing]