painting wall grime

[Fidcal]

I'm trying to make a dirt decal to signify a special painting is missing (this is for something different to the loot painting taken from the frame.) This dirt decal could be used for anything that was against a wall such as if you push a cupboard to one side.

 

But I can't find any reference material and it's hard to visualize. This first attempt doesn't look right somehow. Maybe the dirt band isn't wide enough. Would it be more ragged behind the painting?

 

[Springheel]

Realistically you wouldn't get a dark line like that. The area behind the painting would just be a lighter shade than the rest of the wall. Maybe a very subtle add blend would work?

[Fidcal]

Yes, that sounds right about it being brighter and cleaner behind - though I still think some grime accumulates around the edges. I'm not sure I can brighten the wall without either a custom wall texture or the decal is over the entire wall and makes it darker except for that rectangle. But I'll try add blend on the decal to see if it lightens the wall behind it.

[Fidcal]

yes, blend add works but brightens the whole patch. I might get it to work by extending the grime fading to the edges so there is just enough to exactly balance the brightness. But it won't be ragged. That might be right actually very gradual fade outwardly and softly ragged inside.

 

[STiFU]

I'd suggest to use a more subtle and narrow grime combined with an alphamap so that the borders aren't brightened.

[Fidcal]

I am doubtful that an alphamap will get the fade. I might try again later.

 

The blend add didn't quite work and it also glowed bright in the shadows.

 

So I tried a fainter more graded grime and this is looking more reasonable. It's not lighter in the middle but I am doubtful that can be done except with a custom wall texture.

 

[Fidcal]

I've reduced the borders more and I think this is not too bad. There are two in the screenshot and I think the player is bound to think something used to be there.

 

[Baddcog]

I really don't think it would look like that. That's like dirt was sprayed at the painting, then the painting was taken away.

 

Walls just don't collect dirt around objects. They get smudged from things rubbing against them. They might get bleached from sunlight (but doubtful for stone, even if in a brightly sunlit area) and that would leave a dark patch, not a bright patch.

 

More likely the wall would get washed around the painting (still unlikely) so it would be darker/dirtier under it.

[Springheel]

Stone walls would get dirty from grime and soot, so a painting would block that and leave a light spot. You could do something like a corner grime decal with a square hole in the center.

 

I think the player is bound to think something used to be there.

 

Yeah, if the point is just a player clue, that would do fine.

[Fidcal]

1. This may be the hardest thing I've ever searched for on the net. I have absolutely nothing. zero, not even an ambiguous reference and I've searched for images and I've searched for text. I've tried every combo of key words I can think of. Usually at worst one gets some weak results but I have no results. nothing.

 

2. I've reasoned it out that it is likely there will be different effects depending on age, material, etc. I think a painting or mirror hung in a modern house that is cleaned around every few months and the wall is wallpaper that it might fade and grow dull and dark outside but remain clean and light underneath. Or, in some cases it might bleach faded around the picture and so be more vibrant, possibly darker underneath. If a picture is hung for many years without removing and cleaning around it then dirt may collect around. I've got this idea from somewhere. I didn't invent it. Often one has impressions with no particular memory but I must have seen this many times to be so sure.

 

3. I finally remember I have an old repro on my own wall that hasn't been moved in 15 years. I take it off. And ... da-dah! It has grime around it, more at the bottom than the sides and the sides fade towards the top. I cannot really see any grime along the top. Nor is there any sign of light or dark behind compared to the surrounding wall. I'll check it again in daylight tomorrow. This has hung very near a window but the window faces north and I don't think it ever got direct sunlight.

[Baddcog]

#3 makes sense I guess. Never been in one house for 15 years to check. But usually the painting is hung by a nail or wire so the top may not contact the wall. Hence no dust build up, but the bottom is right against the wall giving dust somewhere to gather.

[Crispy]

Generally a multiplicative blend (blend filter/blend modulate) is used to make textures look darker; blend add is to make textures look lighter. It looks like you're already doing a multiplicative blend in the latest screenshots, so that's good.

 

If you want to brighten up the inside of the framed area, you could use a second decal to add a tiny bit of white to that rectangular area. Or, use one decal with two stages (I think this should work). Too much will make it look washed out though.

[Fidcal]

Committed as decals/dirt/painting_wall_grime as a tga for now. If accepted it can be converted to dds later. Added faint nail hole. Can be rotated upside down and scrolled of the bottom for moved furniture.

[STiFU]

Well, the stonewalls not bleaching argument shouldn't be valid here, as decals are supposed to be general purpose, so they might be as well be used on tapestry or wood. And those latter materials definitely leave a bright spot behind objects, especially on wood. I've seen it myself when moving furniture here and I live in a pretty old farmer's building. I'd say definitely brighten the inside...

[Fidcal]

That will need two decals and I'm uncertain whether even then the brightness might not look unnatural in shadow. It is independent of local light. It is rather like a lit window. I'll try it if I can find time but that doesn't mean other mappers will know or care to use the extra decal.

[STiFU]

Ah yeah I see, that's a problem of course. But it should be possible to raise the brightness of a certain area of a texture properly somehow, without making it full-bright. Maybe you could use a blend-blend-stage with a white texture and an alphachannel, making the inner part semitransparent and a gradient to black at the grime-borders?

[Fidcal]

Just tried this and it does look quite good in a light area. But as I feared, in a dark area it glows. All these blends are not affected by local lighting unfortunately.

[STiFU]

That's uncool, but good to know. The page I linked actually said that already, but I was unsure about its interpretation... This leads to the conclusion that we can only achieve the desired effect in the diffusemap combined with the power of alpha.

 

Diffuse: Centered white rectangle, with dark-brown/grey grain surrounding it, on a black background.

Alpha: Centered (dark-)Greyish rectangle, with white/grey grain surrounding it, on a black background.

[Tels]

I've reduced the borders more and I think this is not too bad. There are two in the screenshot and I think the player is bound to think something used to be there.

 

 

If you make the dirt a bit darker again, the optical illusion alone will make the player think the inner parts are "lighter". Also, if you really wanted, you could add a very very subtle blend-add decal in the center, so it only covers the inner part.

[Tels]

Btw the effect on wether the spot is lighter or darker than the sourrounding depend on different things:

 

* as springheel said, soot collects on the wall and makes it darker. Smokers will know this, their walls fade to yellow while the pictures stay white. Since we are talking about primarily-heated-with-coal buildings here, the effect would be even stronger.

* wall paint gets faded by sunlight. Some colors fade to yellow (leave brighter spot behind the painting), while others actually bleach and fade to white (leave more yellowish spot behind)

* dust/dirt accumulates on the frame (and may get stuck permanently to the wall if it gets wet)

 

In our universe, I think the first effect is much much more stronger, the air has not been that clean in the dark ages as it is now.