Valve's techniques

[Paria]

I was having a look round cp_badlands yesterday to check out how they did the buildings /design/texturing etc, a couple of things i spotted that i didnt really understand how/why

some of the roof's are displacements the ones with /\ shaped roofs - some are displacements others are standard geometry - why?/when? to use each - is it just personal taste or is there reasoning behind it - i've spotted a few feature buildings in well that had displacement roofs in the past, and more intriguing were the roofs that were displacements and made to look like rickety old shacks via displacements, do they use a solid brush and displace all 6 sides? and how do you get it to then look like a /\ shape but with various changes to the levels to make it look like an old rickety roof, being a total nubbin at displacements this left me puzzled

and finally on the sides of the main large outdoor buildings they use 4-5 small window props up near the top - running through the buildings themselves are blocks of no draw that extend into the window itself - behind the building is the skybox - i was expecting some kind of impressive effect when i went back into the game to check what this resulted in - to me they just looked like normal window props

 

[YM]

You can use the 'raise to' feature of the geometry paint to make precise shapes with displacements, its tricky but I'm pretty sure its how they made the huge dish in hydro. so you'd make the displacement and raise the middle row of points most, then the next row slightly less then the next row slightly less untill you have a nice /\ shape, you can of course tweak it slightly afterwards to make it look bent or distorted.

Not sure what you are talking about with the nodraw brushes, they might be to block shadows, vis or just be a guide..

 

[VelvetFistIronGlove]

First, here's a pic that shows what Paria's talking about:

some of the roof's are displacements the ones with / shaped roofs - some are displacements others are standard geometry - why?/when? to use each - is it just personal taste or is there reasoning behind it ... and how do you get it to then look like a / shape but with various changes to the levels to make it look like an old rickety roof

I imagine the choice between disps and func_detail brushes is mostly one of choice. To get that shape though, they would have started with brushes shaped /\, then turned the faces into disps.

on the sides of the main large outdoor buildings they use 4-5 small window props up near the top - running through the buildings themselves are blocks of no draw that extend into the window itself

This is a smart idea, which didn't occur to me but should have. You see, the window props they use have to sit partially within the wall; so you can't make the wall one solid brush or it obscures part of the prop. But if you cut the wall around the window, you can make the face that would obscure the window nodraw. In-game, the window is rendered in that spot so you don't see the HOM. What I have done in the past was cut the wall, and then indent the brush behind the window a little, but unlike nodrawing it, this adds extra faces (and likely another visleaf) just for the window.

 

[YM]

ahhh I see now. yeah I hadnt thought of that either but it does make much more sense.

 

[Paria]

yep that probably explains it, only thing that bugged me was the no clip was partially visible from the outside in my decompiled version- is the vis blocked by something other than the visible part of the model?:blush:

 

[Armadillo of Doom]

I would imagine so. Also keep in mind that decompiled maps often have missing pieces, so you might find anomalies like that.

 

[Half-Life_Maniac]

As for the displacement roofs, I believe displacements are cheaper to render than plain old world geometry, or func_details. That'd be one reason for using them. I could be mistaken however..

The most obvious reason though, would be for adding all dents and twisted bits in those old tin roofs. This can of course be done with multiple brushes, but again, the diplacement would be cheaper.

 

[Vilepickle]

Most likely the sole reason for using a displacement roof like that is because of those detail supports. If the roof were a brush, the "waterindices" (which increases with the more T-Juncs you have) would probably go up on the summary list, which is fairly easy to max out with a lot of detail (I did it with Castle). The intersections with the detail supports would raise this number, and they obviously have a boatload of other detail throughout the level, so it's just budgeting.