A couple general environment art questions

jordank95

Hi guys. Just a couple general questions regarding environment art. 

1. I see people talk about using a “second UV channel” for things like rocks. Is this the same as just overlaying a tiling detail normal on top of your base textures in UE4? 

2. When building modular, I see people say “it will scale up nicely” when using a power of 2. I get the principle behind that. But Why would you want to scale up any modular pieces at all? Like buildings or interior modular pieces, why would those ever need to be scaled up or down? 

Neox

regarding 1. usually the second channel is used for lightmap info
2. not sure how it corelates with power of 2, i guess i would need more context

Obscura

1. ^
2. No that would be dumb. All game engines uses metric unit system now. So then if you would have a 128 unit length wall you would need to apply 0.72 scale to get a 1m wall. However, having a 1m wall would enable you to easily scale to 2m, 3, or whatever, with simple numbers and no math needed.

Eric Chadwick

Powers of two for texture sizes, yes. For model sizes, no.

Mark Dygert

1) Like Neox said the 2nd UV channel is usually reserved for lightmaps. Some engines create this channel for you and do an automatic unwrap of your objects which in most cases works just fine so you don't even need to think about any other channel than the first. The automatic unwrap will assume that every face is equally important and it will add a significant amount of padding which is usually just fine but there are some models where  you might only really care about shadows on a handful of faces so you scale those up and the rest can be scaled down. Engines don't know about that kind of prioritization... yet... so you have to handle those cases on your own.

You can add a 3rd or a 4th channel to do different kinds of blends if you need to. It does add to the overall vert count of your model and there are some shader/rendering costs associated with extra UV channels but that doesn't stop you from doing it when you need to.

More info about lightmaps in Unreal:
https://api.unrealengine.com/INT/Engine/Content/Types/StaticMeshes/LightmapUnwrapping/index.html

2) I haven't heard of too many modular systems being built with power of 2 dimensions. That seems kind of odd. I can see scaling organic sets like rocks, rubble, cliffs, dunes, bushes and trees but I don't see how power of 2 would play into that. There might be some obscure mathematical reason? I would definitely ask more questions of whoever was saying that.

jStins

Mark Dygert said:

2) I haven't heard of too many modular systems being built with power of 2 dimensions. That seems kind of odd. I can see scaling organic sets like rocks, rubble, cliffs, dunes, bushes and trees but I don't see how power of 2 would play into that. There might be some obscure mathematical reason? I would definitely ask more questions of whoever was saying that.

Wasn't the grid in UE3 based on powers of 2? As in the default grid could be changed to 8, 16, 32, 64 units etc... Maybe OP came across some older material about 'staying on grid' and the powers of 2 values caused some confusion. Just a guess... 

zachagreg

Obscura said:

1. ^
2. No that would be dumb. All game engines uses metric unit system now. So then if you would have a 128 unit length wall you would need to apply 0.72 scale to get a 1m wall. However, having a 1m wall would enable you to easily scale to 2m, 3, or whatever, with simple numbers and no math needed.

I have heard about people using power of 2 grid because it makes all of your textures equally divisible, or because it maintains a texel density of 1 pixel per cm or something like that because it's cleaner but that goes out of the window as soon as you up the texel density so I don't know. 

I do know that you can set UE4 to use a power of 2 grid as well since UDK used this. But that doesn't change the rest of the scaling in Engine so now like you said you're just doing calculations on everything. Again it just makes everything more complicated to build. Especially for corner or non-straight pieces. Metric is just easier. 

This article states otherwise though so *shrug*
https://www.gamasutra.com/view/feature/130885/creating_modular_game_art_for_fast_.php

poopipe

that article was written in 2005 

zachagreg

poopipe said:

that article was written in 2005 

tru