Need advice on approaches bevel the geo or use normal map for bevels? and some workflow questions

lockey1995

Hey all, 

Not been on here for a while I actually took a little break for a while and I've come back I've been doing more higher poly product viz style, but i seem to be jumping around everywhere currently and it's always good to learn .  Anyway before I start happy new year to you all . 

Ok so I'm going back on re doing one of my mod tracks for assetto corsa (Racing game)  now i feel more comfortable on the modeling front the only thing I'm confused about is how you'd generally go about approaching assetts in terms of beveling the geometry it self or baking out a normal with the bevel. So i did have a little play around the other day with a crash barrier and a quick electrical box I knocked up. I'm just confused on which methods to use I stil lurk here allot and the amount of information is overwhelming with all these techniques etc. I'm guessing on some it's multiple factors dictated by a team so it'd be tricky to figure out your own. 

The first image i have two the one at the front is baked with a unique uv and the second one is I think medium poly? with a trim as I didn't feel it really needed unqiue detail.  I've read on here personally found that one faster to do than the sub d for the bake. The bake isn't the best as i whipped it up pretty quick lol. I've heard the medium poly models can be tricky to lod out though? 

I've been using trims now and I did on another track i did for someone following polygonacademys tutorial minus the z brush and that sped things up for me big time. So in closing yeah my main question is what dictates the approach you take? I think one takeaway i've definitely learned now is plan,plan,plan which i don't do enough of. 



Here is the second example of the electricbox 


A trim I did from a previous project:

poopipe

Block it out roughly and test it in game.  If you don't get close enough to see the geometry you'd put in for a bevel, the geometry doesn't need to be there

lockey1995

poopipe said:

Block it out roughly and test it in game.  If you don't get close enough to see the geometry you'd put in for a bevel, the geometry doesn't need to be there

Cheers that clears up a few things , the barriers you can actually see pretty decently with a bevel when drifting around and i think it does look better. So i will keep it in for that and the basic trim style texture other stuff I'll be pre planning with your advice

lockey1995

poopipe said:

Block it out roughly and test it in game.  If you don't get close enough to see the geometry you'd put in for a bevel, the geometry doesn't need to be there

I do have one question that's been bugging me, i'm totally new to lods overall pretty much and never even added them before oops. It still ran well but i would like to learn what's the best approach? I'm on Maya if that helps but what was bugging me is how could i lod on a bevelled model? 

I'm guessing lod 0 is your main model and you'd want lod 1 with no bevels at all.

Eric Chadwick

poopipe probably has more experience with LODs, but here's my 2 cents.

LODs can be pretty aggressive in a racing game, as the player is generally moving quickly, so popping is less obvious.

You can probably just lose those bevels in the second level (LOD1). 

If you baked the bevels, you could reuse the same normal map, and see a blurred bevel. Or you could simplify the LOD1 shader and drop the normal map completely.

gnoop

Smooth lod switch is extremely important for a racing game as Eric said.   Geometry bevels you do on  such objects  usually have to be propagated up to  next few lods.   Otherwise  you instantly see certain shading switch.     So my choice usually is bevels baked into normal maps .  Even if it looks not that great  at close.  

If you want visible geometry bevel at close  and the normal map is still necessary   some clever  normal editing   keeping vertex normals  close to what  next lod would be  could make the trick .

   But it does take time and  requires a lot of  thinking beforehand .    Usually you have to think  at lod02 level when baking the normal map.        Don't expect it to be perfect  in all situations anyway.   So it rather a strategy question  of work hours vs quality.

lockey1995

gnoop said:

Smooth lod switch is extremely important for a racing game as Eric said.   Geometry bevels you do on  such objects  usually have to be propagated up to  next few lods.   Otherwise  you instantly see certain shading switch.     So my choice usually is bevels baked into normal maps .  Even if it looks not that great  at close.  

If you want visible geometry bevel at close  and the normal map is still necessary   some clever  normal editing   keeping vertex normals  close to what  next lod would be  could make the trick .

   But it does take time and  requires a lot of  thinking beforehand .    Usually you have to think  at lod02 level when baking the normal map.        Don't expect it to be perfect  in all situations anyway.   So it rather a strategy question  of work hours vs quality.

Cheers, yeah makes a little more sense now considering it's one thing I've never done. So ideally I'd need to create them by hand not use mayas reduce tool etc?

poopipe

Definitely lod hard surface stuff by hand, it's not worth the hassle of using autolodders 

Your basic aim with lodding is to ensure that you never have a triangle on screen that is smaller than a pixel - that's the point where things become inefficient to render. 
As such you will likely want to drop thin bevels at the first lod but as with everything else it's really just a case of iterating carefully on a few assets until you get a feel for what works for your circumstances. 


Despite the fact our two esteemed colleagues appear to be arguing opposite points I'd suggest they're both correct.

Gnoop makes good point about shading pops - these will be very obvious on shiny stuff like barriers. 
 my (albeit  limited ) experience with fast paced games is that you tend to notice that more than you do popping based on silhouette - which supports Eric's position.

You can mitigate against shading pops and be very aggressive with lods if you project normals up the lod chain - i.e you bake to a low(ish) lod and project it's mesh normals onto higher lods rather than baking to the high lod.

As an example...
Let's say you choose to remove the ripple shape from your armco barrier at Lod 3 - this naturally changes the way light interacts with the surface when lods switch from 2-3 quite dramatically. 
But...
If you bake your high Res to the Lod 3 mesh and project mesh normals from that up to lods 2,1 and 0  you'll see no (or at least minimal) change in lighting when the lods switch. 

 

gnoop

 I still suggest  to  bake  to lod01 or lod02.   Lod 03  may just have not enough geo to support proper baking at all.     Just edit/project vertex normals  the way  they  would stay  in same direction through lods.    I usually just  copy/paste vertex normals  from one lod to another.    Thanks to Blender it's IMO easier there than in Max .   

 

It sometimes makes those bevels baked into normal maps  look less perfect shading wise  i.e  still with seams due to more extreme angle  with now strongly edited vertex normals .  

From what I remember about U4 engine  they may look perfectly ok  initially  but once you have  screen /distant field /whatever  ambient occlusion  on,   they are not that perfect anymore.  Check it on your own .  Kind of another reason for not baking  the normal map for too distant lod

Anyway you would usually end up with redoing your lods several times and solving this puzzle for each and every thing.    Yeah. nothing is easy in racing genre    Even those damn barriers which may look simple like 2x2 initially.