How will bullet hole decals work for thin walls?

[Revenge]

Well seeing as HL2 is using the same bsp system to make it's maps leaves some very big problems when trying make real time holes on a surface. Denting is considerably easy if we think in terms of HL1 style mapping (since they apparently wont be all that different).

Now, to create this effect in HL1, you'd have to do it while making the map (ie not real time). In HL2, seeing as we're following the map design rules it's fairly safe to say that basically the HL2 engine would need to do in real time what the HL1 engine could only do in the editor.

Now as for the hole itself. The easy way in HL1 was to make a texture that had transparent bits in it. That's how they made chicken wire fences and glass. You'd take a normal texture, and draw little blue circles on it, which would appear as transparent holes in HL1 if you had the right settings on while making the map. Simply flip the texture on the other side of the surface and you'll have holes that line up convincingly. (But you can't shoot thru em).

In HL2, this means that the engine would need to basically edit textures in real-time, however doing that would mean that you would either need a completely separate texture for every surface (meaning you run out of ram in a hurry), or you get a very strange looking effect where shooting one fence will create identical holes in every other single fence using the same texture...

To make a real hole is even more complicated, because of how faces are split up and other annoying engine problems you quickly pick up as a mapper... Basically real time holes would create many many many more polygons than the map started out with, most of them being completely in line with the next, so you wouldn't even be able to see where one polygon ended and the next started... But they would still slow the game down something ridiculous...

Then there's the old HL1 problem of not being able to create any surface that was less than one unit in any dimension, and so unless they fixed that, it'd be impossible to create any round hole unless every surface on the inside of it was atleast a 1 inch square... You can easily see the width of of the hole having a minimum size of 1.5 inches or so... MUCH bigger than any real bullet hole...

 

[Wesisapie]

take a look at the video bit with the ant lions, as the first poster said, the bullet holes aren't just 2 decals, they look like the metal has been torn from the bullets, which to me suggests there would be a hole there.

 

[Lifthz]

Originally posted by Peks
making holes in walls/deforming the map = bad multiplayer gameplay

you're kidding right?

 

[PSX]

Originally posted by Lifthz
you're kidding right?

if you've ever played Red Faction with the geomod tech online, then you'd think someone would be nuts to have deformable terrain... even the developers were smart enough to have certain walls and floors to be untouchable, but still, at the end, there was so much mayhem and obstacles created after a firefight, it turned out rather pointless; I just hope Valve knows what they're doing in this aspect, 'cause with 10+ ppl you will have tons of lag (respect the dial-uppers), especially if you use a bad method of what to be server/client-side, etc.

 

[Lifthz]

I've played Red Faction. It was alright. But the gameplay mechanics itself is just boring. Average FPS.

It doesn't mean that being able to shoot through walls is bad, Red Faction did it in a totally un-natural and ... just boring way. Lol. If it was done for Half-Life 2 it wouldn't be like that, it would be more realistic.

 

[Xtasy0]

Originally posted by Wesisapie
take a look at the video bit with the ant lions, as the first poster said, the bullet holes aren't just 2 decals, they look like the metal has been torn from the bullets, which to me suggests there would be a hole there.

thats the thing, the decals look real enough to make you think there is a hole, so whats the problem? there is no hole

 

[Peks]

Originally posted by Lifthz
you're kidding right?

no, imagine on a map that last 30 minutes...how many holes and bullshit are all over everywhere. players making theyr own paths through the map is silly..and takes away from the chokepoint combat.

 

[Lifthz]

I think I was right...

TAKE A LOOK at the video at the Ant-Lions scene. When those automated guns are shooting, they shoot holes straight rhough that door frame...

Originally posted by Peks
no, imagine on a map that last 30 minutes...how many holes and bullshit are all over everywhere. players making theyr own paths through the map is silly..and takes away from the chokepoint combat.

I dunno man, we'll see... I think the way you're thinking of it could be wrong though.

You wouldn't be able to shoot through everything. Unless everyone has rockets and grenades.

I think being able to have a little power over the map itself could be interesting, and could open up new possibilities.

 

[Peks]

Originally posted by Lifthz
I think I was right...

TAKE A LOOK at the video at the Ant-Lions scene. When those automated guns are shooting, they shoot holes straight rhough that door frame...




I dunno man, we'll see... I think the way you're thinking of it could be wrong though.

You wouldn't be able to shoot through everything. Unless everyone has rockets and grenades.

I think being able to have a little power over the map itself could be interesting, and could open up new possibilities.

you are...hit decals appear on the players side of the doors...opposite the side of the automatic guns. but they are only hit decals..nothing tranparent.

 

[Sherrill]

I dont know but I hope they fix the part in the tech demo where he is going through the city...If you watch when he is on top of the roof and they are firing up at him that the bullets go through that metal dumpster he flips on them...

 

[dscowboy]

Originally posted by FictiousWill
I think all the displacement map would allow you to do would be to make bullet indentations in walls.

(Can a wall/floor/surface have more than one displacement map? If yes, then do they add to eachother? Usability and effects-wise, the answers to these questions hopefully are yes, then no, respectively.)

I don't think displacement maps in HL2 are that dynamic. I think you have to assign displacement maps in the editor like textures, and then in game you can switch between 'on' and 'off'. I don't think there's a way to dynamically create a displacement map for a surface in-game.

Originally posted by FictiousWill

Just for the heck of it, I drew a picture of the only decal method that would work as a render pipeliney flowchart thingy - I used this method in a d3d8 game on a less interactive level a while ago. It's not worth the effort, and it doesn't look that great. I would much prefer displacement map indentations.

I like your solution, very creative.

 

[AH_Viper]

To start off, im talking about the likes of 5.56 rounds and such, not huge holes.

Right, im thinking about this 3D texturing that is possible with DX9.

Im not sure atall how it works because i really dont have a clue and this is second hand information here, but there was a 3D cube made of marble that was cut in half to show that the texture went all the way through.

Sooooooo why not made a decal that has a depth of the wall.

In theroy its easy enough. For a start, 5.56 rounds can only go through thin-ish walls. So say the wall was 10cm thick just make the decal for that wall 10cm thick.

Tell me if im wrong here

 

[Lifthz]

Originally posted by Peks
you are...hit decals appear on the players side of the doors...opposite the side of the automatic guns. but they are only hit decals..nothing tranparent.

Well they look transparent to me. I see a hole, not just a standard decal.

It would be better to tell from higher res footage or actually playing though.

We'll see.

 

[mercer]

If you've got a wall which is only a single plane with a two-sided texture, an alpha map for tansparency would create a hole you could actually see through. (similar to how a lot of foliage is created with just a few polys). How you would overlay this with the existing texture I'm not sure - I'm not really an expert on these things.

AH_Viper - the cross section thing you saw was (I think) a layering technology geared towrds medical imaging I read about somewhere. Either that or it was referring to procedural textures - but these are still geometry dependant - they just don't need mapping coords and do "run through" the geometry.

Hope this is helpful!

Edit - oops, just realised Revenge already said a similar thing about alpha maps. Sorry dude.

About displacement - you can use texture maps to distort geometry (though not create holes) in regular 3d programs like 3ds max, but with fairly high render times. I don't know exactly how this relates to game engines.

 

[Revenge]

Yeah except I didn't know they were called alpha maps

You learn something new every day!

 

[Guest]

I think th game was on its 67.3% texture and polys so maybe in the full version game will be this full damynamic shadows:cheers:

 

[DESSTROYER]

yeah i would like something like that in hl2 or maybe like a wooden door u can have a oicw or some heavy assault rifle or machine gun and shoot the door till it breaks into pieces i made a flash movie but its pretty crappy took me like 5 minutes to make just to show how id like to see it in half life 2 (and i said its crappy it took me 5 minutes)

 

[FictiousWill]

Sooooooo why not made a decal that has a depth of the wall.

I don't quite think you understand how the displacement maps work. So hey! I'll draw a picture! hooray!

Bullet holes done this way could still use alpha penetration effects, and be "3D," without the computational load on the processor, or the 'can see through even when not looking straight' problem. It's a pixel shader effect similar to bump mapping, so it would probably be a higher video card option. I would be pleasantly suprised if this technique is used in HL2, as I believe it to be quite feasable.

edit: I just watched that flash movie, DESSTROYER, and I understand completely what you mean. That's the main problem with the previous double-alpha decal method I described, because shooting the door in half would not cut it in half (it would only draw a transparent line through the middle) Unfortunately in order to achieve such an effect hoardes of cpu power and memory is necessary because the door essentially has to be built out of separate particles.

 

[PSX]

I would be pleasantly suprised if this technique is used in HL2, as I believe it to be quite feasable.
you mean you wouldn't be surprised if this technique is going to be used in HL2?

 

[FictiousWill]

No, I would be - it really isn't a super-necessary or easily noticable effect (like ragdoll enemies are, for example) I think its a toss up as to which effect they use; standard decals or displacement map decals, but I hope they use displacement map ones just because they can with the engine (I mean they might as well, you know? )

 

[AH_Viper]

I wonder how the wood worked in the tech demo.... that seamed to pretty pixel perfect breaking in two.

Anyone know how accurate that was and how it worked?

 

[Revenge]

Well the wood is an interesting one.

According to Gabe, if you wanted to have a wooden table where you could shoot out one of the legs and have the rest of the table fall over and sit on a lean, you'd need to have created each of the legs and the table top separetly in the map editor.

Basically when you shoot a wooden object, the whole object is destroyed. The amazing wood-chipping thing-a-ma-bla must therefore be similar to rag-doll animations on dying characters. It just makes it's "death" look pretty damn cool.

My interpretation:
If I was to create a wooden fence in my map, and each plank on the fence was one object, then shooting one plank would break that plank in two where I shot it, and both pieces of the plank would fall down and be "destroyed" similar to the bits of crate in HL1 that you could keep chopping down to size after you destroyed the crate...

Similarly I could make the entire fence out of one object, and the entire fence would be destroyed when I shot out one plank.

More interestingly however, I could create each plank on my face out of 3 objects, and so when the player shot a plank, only a third of it would break away, and the peices around it would act realistically according to physics. Apparently I can even set up parent/child relationships with the individual plank pieces to each other, and to the fence posts too. Meaning I could attached them to each other as if they really were nailed on!

 

[FictiousWill]

That hits the nail on the head - that is almost without a doubt the way it will be done. Using more objects won't really be a problem either, becasue if your computer is up to playing HL2 in the first place, it shouldn't moan and groan about larger numbers of objects.