Lighting:Leaks - Revision history

JRandomNoob: Completely replaced the original folk mythology. Long live the Truth!

2013-11-30T19:05:00Z

Completely replaced the original folk mythology. Long live the Truth!

Rylius: added category

2011-08-19T14:25:17Z

added category

John: /* Common causes of light leaks */

2011-08-19T13:33:00Z

‎Common causes of light leaks

John at 13:16, 19 August 2011

2011-08-19T13:16:45Z

John at 09:58, 19 August 2011

2011-08-19T09:58:04Z

John at 09:47, 19 August 2011

2011-08-19T09:47:25Z

John: Created page with "Light leaks are an annoying side effect of the way the compiler works. With a little care this can generally be avoided at construction time but can be very difficult to fix retr..."

2011-08-19T09:45:19Z

Created page with "Light leaks are an annoying side effect of the way the compiler works. With a little care this can generally be avoided at construction time but can be very difficult to fix retr..."

New page

Light leaks are an annoying side effect of the way the compiler works. With a little care this can generally be avoided at construction time but can be very difficult to fix retrospectively.

It's much easier to be aware that light can leak in your map and construct the map in a way to avoid this.

==Common causes of light leaks==

*Bright lights in confined areas will almost always leak, try to avoid large single light sources, use smaller values and more of them
*Shared floors.

Shared floors will also almost always leak light somewhere. A shared floor

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-{{WIP}}
+The so-called “light leaks” and their shadowy brothers aren’t actually caused by the compiler casting rays through walls and ceilings; rather, these are an inherent artifact of Quake 3 lightmaps. Lightmaps are simply compiler-generated images that are blended with the textures to darken, lighten and/or color them. In Quake 3 and UrT lightmap images are restricted to 128×128 pixels (and uncompressed TGA, which is an issue in itself) and usually a single image is cut into many pieces, each covering a specific small area. “Small” is of course relative here, the lightmaps have to be scaled up a lot — even at '''<tt>_lightmapscale 0.125</tt>''' one pixel has to cover 2×2 units of surface.
-Light leaks are an annoying side effect of the way the compiler works. With a little care this can generally be avoided at construction time but can be very difficult to fix retrospectively.
+[[File:lightmap_0021.png|frame|128px|A typical lightmap image (a map usually contains a few dozen of them). The color splash is caused not by a light entity but a nearby bright-colored surface coloring the reflecting skylight (only happens with -bounce).]]
-It's much easier to be aware that light can leak in your map and construct the map in a way to avoid this.
+The compiler tries to map surfaces that are similar in proximity and directionality onto continous lightmap pieces — i.e. a floor and the ground outside (even if these are separate brushes with a gap between them) might be covered with a single lightmap piece. The stronger the lighting contrast is the more the lit side of a single lightmap piece tends to “push” into the shadow (a common knowledge among mappers is that the best way to avoid light leaks is keeping light levels the same throughout the map, which of course can make it look bland and boring).
-==Common causes of light leaks==
+''This'' is what causes light and shadow leaks. The distinction is subtle but important — were the light actually leaking through solid brushes there would be nothing you could do, but forcing the compiler to map things differently is dead easy.
-*Bright lights in confined areas will almost always leak, try to avoid large single light sources, use smaller values and more of them
+Let’s take the most common scenario: a room with light leaking in from under the walls. To fix this, you simply select the affected floor brushes and make them a separate func_group — this forces the compiler to map this surface separately. Quite often this is enough in itself, but if you still see some leaking (this time because the lightmap can’t be scaled to ''exactly'' cover the whole surface at this lightmapscale) you can specify a separate <tt>_lightmapscale</tt> for the func_group (0.5 is good enough for most cases). This method solves the vast majority of light and shadow leaks.
-Shared floors, walls or ceilings will also almost always leak light somewhere. A brush that is used in 2 rooms will encourage light to travel along the length of the brush in relation to the strength of the light.
+There are some other ways a light leak can happen though, for example if you have a sky brush resting on top of an accessible building you definitely have to caulk the underside that’s touching the roof. (This kind of leak is in fact as close to light travelling through solid brushes as it gets.) Of course, if you see a very bright and obvious leak that resists all your attempts to get rid of it you most likely have an actual gap between the brushes;-)
-To avoid this specific problem, use smaller brushes, several rather than one for the ground, wall or ceiling plane.
+Note that it’s impossible to fix leaks from under (rotating or sliding) doors — entities like these are completely ignored by the compiler and the light indeed does behave as if there was nothing in the way. Your best bet in those cases is ensuring that the light levels on both sides of the door are as close as possible.
 [[Category:Lighting]]

← Older revision		Revision as of 14:25, 19 August 2011
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	==A practical demonstration, 2 rooms==		==A practical demonstration, 2 rooms==
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		+	[[Category:Lighting]]

← Older revision		Revision as of 13:16, 19 August 2011
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	{{WIP}}		{{WIP}}
		+	''Light leaks are when a light in room a spreads under walls to room b,''

	Light leaks are an annoying side effect of the way the compiler works. With a little care this can generally be avoided at construction time but can be very difficult to fix retrospectively.		Light leaks are an annoying side effect of the way the compiler works. With a little care this can generally be avoided at construction time but can be very difficult to fix retrospectively.

← Older revision		Revision as of 09:58, 19 August 2011
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−	~~Johnny working on this.~~	+	{{WIP}}

	Light leaks are an annoying side effect of the way the compiler works. With a little care this can generally be avoided at construction time but can be very difficult to fix retrospectively.		Light leaks are an annoying side effect of the way the compiler works. With a little care this can generally be avoided at construction time but can be very difficult to fix retrospectively.

← Older revision		Revision as of 09:47, 19 August 2011
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		+	Johnny working on this.
		+
	Light leaks are an annoying side effect of the way the compiler works. With a little care this can generally be avoided at construction time but can be very difficult to fix retrospectively.		Light leaks are an annoying side effect of the way the compiler works. With a little care this can generally be avoided at construction time but can be very difficult to fix retrospectively.

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 *Bright lights in confined areas will almost always leak, try to avoid large single light sources, use smaller values and more of them
-*Shared floors.
+*Shared floors.walls or ceilings
-Shared floors will also almost always leak light somewhere. A shared floor
+Shared floors, walls or ceilings will also almost always leak light somewhere. A brush that is used in 2 rooms will encourage light to travel along the length of the brush in relation to the strength of the light.