LOD Meshes and Normals/MIP maps...

Hanzz

Been trying to figure out something for awhile now.

Since normal rendering is the result of model surface normals co-inciding with normal map data burned from a high rez mesh into the normal map, LOD meshes present a problem. When the game switches from LOD-0 to LOD-1, the reduced polygonal data of the LOD-1 mesh will no longer co-incide with the normal map as originally burned, and will cause softening of edges. So...

Is there some way to manually pack individual normal maps into a MIP map, each one burned individually from the surface of LOD meshes? Or is there some other way around this that I'm not aware of...?

Quack!

Hanzz wrote: »

Been trying to figure out something for awhile now.

Since normal rendering is the result of model surface normals co-inciding with normal map data burned from a high rez mesh into the normal map, LOD meshes present a problem. When the game switches from LOD-0 to LOD-1, the reduced polygonal data of the LOD-1 mesh will no longer co-incide with the normal map as originally burned, and will cause softening of edges. So...

Is there some way to manually pack individual normal maps into a MIP map, each one burned individually from the surface of LOD meshes? Or is there some other way around this that I'm not aware of...?

You are talking about a unique new texture created for each LOD. This may never happen in a production environment, way to time consuming and resource intensive for very little payoff.

If this is for a portfolio, just don't use lod's.

Neox

it's not entirely unlikely to hapen, you can pack the lod normalmap into the mipmaps.
And i saw this happen in productions - with the dds plugin for PS you can do it by hand.
but this should happen automatically and not be done by hand at all - it's been some time since we last did LODs by hand, many productions use simplygon these days.

thankfully

Hanzz

Thanks for the info. I guess if an art director is wanting to avoid unnecessary collapse of LOD meshes, hand-reduction is still the only recourse. I just chafe at the idea of having to burn 4 normal maps to avoid softening of edges on increasingly reduced meshes. But looking back at my AGR art test, only the very lowest one really shows it. Any thoughts on using just 1 smoothing group on a model versus uv-matching smoothing groups? For me, I try to eliminate compound vertex streams wherever possible, and 1 smoothing group helps that effort over having multiple SG's.

EarthQuake

The thing with LODs is they pop in when the model isn't taking up much screenspace, so the nastyness of the lowpoly no longer matching the high is usually moot at that point.

Even if you packed LOD normal maps into the mip chain, you would run into all sorts of other problems. What if your LOD mesh and Mip settings don't match exactly? Then you've got the wrong map on the wrong model anyway. What if the player turns down the texture quality settings? Now you've got an LOD normal map applied to the highest geometry level, which would be much worse than the other way around.

Hanzz

hahahah! Good points, indeed. Hmm. So it might be better to leave mips levels to themselves. Here's hoping the Unity engine (not my preference, btw...) handles LOD efficiently and cleanly. Thanks for the insights, guys.