blendLight blend lights - what is that?

[motorsep]

I searched the forum, but couldn't find a good example explaining that blend lights are for and how does it look like compare to normal lights. DarkMod wiki doesn't have info either, D3W is dead, Doom 3 has no blend lights.

 

I noticed RAGE used quite a few of those.

 

So my questions are:

 

1. What do blend lights look like compare to normal ? (please post an image)

2. What are the common uses for blend lights ? (please post an image)

3. Are there any specifics about preparing assets for blend lights (besides having blendLight key in the material) ?

 

Thanks a bunch!

[nbohr1more]

Blend lights are lights that don't calculate directional shading on normal maps or perform any of the standard light interactions. They simply take input textures and perform OpenGL blend operations. They are typically used for fog, glare, or projecting effect decals over moving geometry. They can also do a pretty good job of faking shadows except in cases where associated light sources move relative to the shadowed object. As I recall, Doom 3 supports every OpenGL blend operation in the ARB 2.0 specification.

[motorsep]

Blend lights are lights that don't calculate directional shading on normal maps or perform any of the standard light interactions. They simply take input textures and perform OpenGL blend operations. They are typically used for fog, glare, or projecting effect decals over moving geometry. They can also do a pretty good job of faking shadows except in cases where associated light sources move relative to the shadowed object. As I recall, Doom 3 supports every OpenGL blend operation in the ARB 2.0 specification.

 

Half of that sounds like taken directly from wiki, sorry to say that :/ I'd really appreciate someone showing screenshots with blend lights in use, vs normal lights.

[nbohr1more]

I think there's a few screens of blendLight fog in the SEED thread in the editor forum and Springheel posted images here:

 

http://forums.thedarkmod.com/topic/16303-projected-shadows/page__view__findpost__p__347267

 

of a blendLight shadow.

 

I will try to find some more examples when I get a chance.

[SteveL]

I can't post a pic, travelling again, but they are not really interchangeable with normal lights anyway. They are more like a way of projecting a decal (the light texture) on to a surface. You can use them for performant shadows with a fixed shape like in Springheel's example linked above, or for the pattern of coloured light cast through a stained glass window, that kind of thing.

[motorsep]

I think there's a few screens of blendLight fog in the SEED thread in the editor forum and Springheel posted images here:

 

http://forums.thedar...post__p__347267

 

of a blendLight shadow.

 

I will try to find some more examples when I get a chance.

 

Thanks. How come that image doesn't affect candle stand, and is "projected" only on the table ? Is it just being drawn where light's volume "touches" a surface ?

 

I wonder if I can use blend lights as decals, since they get automatically projected over any complex surface vs using standard methods of decaling. Are lights included into entity count limit ?

[motorsep]

I can't post a pic, travelling again, but they are not really interchangeable with normal lights anyway. They are more like a way of projecting a decal (the light texture) on to a surface. You can use them for performant shadows with a fixed shape like in Springheel's example linked above, or for the pattern of coloured light cast through a stained glass window, that kind of thing.

 

I'd appreciate it.

 

Btw, wouldn't it be exactly the same as using projected standard light to cast colored light onto a surface ? (as in your example, stained glass like in churches)

[HMart]

I'd appreciate it.

 

Btw, wouldn't it be exactly the same as using projected standard light to cast colored light onto a surface ? (as in your example, stained glass like in churches)

 

The difference between a standard projected light and a blend light is that it has no interaction with the surface materials at all, this is what the id documentation says about it " Perform simple blending of the projection, instead of interacting with bumps and textures"

[motorsep]

The difference between a standard projected light and a blend light is that it has no interaction with the surface materials at all, this is what the id documentation says about it " Perform simple blending of the projection, instead of interacting with bumps and textures"

 

You can turn off shadows, spec, etc. on standard light and will have no interactions either.

[HMart]

You can turn off shadows, spec, etc. on standard light and will have no interactions either.

 

That is perhaps why id didn't used blendlights that much on Doom 3, why they used more of them on Rage (has you said) is beyond me, perhaps a blendlight on idtech 5 behaves differently to one on idtech 4?

[motorsep]

I don't know much about RAGE modding (rather nothing at all). I checked out images for blendlights and they used it for shadows too, particularly for Authority's drop ship.

 

I just wonder if lights are accounted for entities. If now, blendlights would provide us with really nice way of decaling levels.

[nbohr1more]

I'll have to check my sources but I'm pretty sure they are considered entities. Doom 3 assigns a small AI routine for lights and TDM has extended that to some

degree for extinguish attributes and dynamic ambient zones. Whether lights can be grouped together to form a super-entity? Not that I recall but I know that

we often simulate this behavior by making entities with multiple flame particles or emissive textures and then have one real light attached to that entity with

a radius that covers what all the sources combined would emit. These entities also extinguish all the particles when hit by water arrows (etc). If it were possible to

make a super-entity of lights then I think that such workarounds would not be the norm, though I'm not sure if it's ever been broached?

 

Still, for some decal operations you "might" still save a little performance with BlendLights because they don't need the patch geometry as the decals would...

 

Hmm... with vanilla Doom 3, I wonder about their comparative memory and PCIE footprint since (presumably) you wouldn't need to feed the skinned decal patch

geometry over the bus...

[HMart]

I don't know much about RAGE modding (rather nothing at all). I checked out images for blendlights and they used it for shadows too, particularly for Authority's drop ship.

 

I just wonder if lights are accounted for entities. If now, blendlights would provide us with really nice way of decaling levels.

 

BloodRayne that developed the Grimm Quest for the Gatherer's Key mod made a nice ingame dynamic decal system

 

I've implemented a new feature into Grimm:Quest for the Gatherer's key that I'm very excited about. It's simply called 'spray painting' and what it does is allow for mappers to run their map and spray paint the world with decals. No more tedious placing of single plane decals to create static blood, but 'real' painting of the world with decals. I can now run a map, think 'I'd like to have some blood spray there', paint the world with a single click, issue the command 'saveDecals' when I am happy with the result and the paint will be there permanently in the map.

 

To make this happen I have exposed a new script command via the SDK that calls 'projectDecalOntoWorld'.

I use this routine in a very simple entity called 'grimm_spray' which has several advantages over the regular func_spray.

The first advantage is that I can now use random paint decals, allowing for randomly looking worlds (which is what Grimm is all about).

The second is that players can turn the feature off, meaning that they can remove these decals for performance reasons, something that's not possible in a static map.

When painting mode is not set, the spray entities spawn during mapload and paint the world, after which they are automatically removed, this will leave only the paint decal.

Players can set paint density, to have either more or less paint in the world.

 

I'm pretty excited about this, I've managed to go over 6 maps in a matter of several hours and completely detailed them to taste with decals. This would have normally taken more than a week of careful placing of single decals by hand in the editor, with the added disadvantage of blood not spraying onto nearby objects and such.

[OrbWeaver]

You can turn off shadows, spec, etc. on standard light and will have no interactions either.

 

You can turn off the advanced features of regular lights but they still perform the same basic function of a light. A regular light can never make a surface darker, which a blendLight can. It can also be used to produce certain effects like "washing out" the colours inside its volume. I did make a post some time ago with screenshots of a few of the possible effects of a blendLight, but the forum search is utterly useless and I can't be bothered to manually view my entire posting history in the hope of finding it. Here it is: http://forums.thedar...post__p__180933

[motorsep]

Oh, looks like fake color grading effect Neat!

 

So if it's a volumetric effect, how would I be able to make a decal with it? By having projected light to be a blendLight ?

 

Btw, how do you setup the blendLight to make surface darker?

[motorsep]

Bump!

[Springheel]

You use a blend filter stage. It's in Orbweaver's link.