Normal map issues.

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How Normal maps work is complicated, who knew? :P

So there’s been an issue I’ve noticed with normal maps which I could not figure out.  I know not too many people around here use normal maps as regularly or as extensively as I do but I figured I’d post this in the event someone else runs into this issue and it could save them some time figuring out what’s happening.

So basically any edit, or resizing of a normal map I’ve generated will cause the way the map displays to break, or at least how’s displayed in 3ds max.

I found some relevant information on editing/resizing normal maps here, unfortunately this was not the cause of my issue but is still worth reading:

http://www.bencloward.com/tutorials_normal_maps12.shtml

I made a post on the auto desk forums asking for help where a solution was posted for me:

https://forums.autodesk.com/t5/3ds-max-forum/problems-resizing-editing-normal-maps/m-p/9305841/highlight/false#M183454

It turns out the cause was 3ds max’s gamma/LUT correction.

 

 

I’ve also been trying to research/experiment with methods of baking hard surfaces.  With normal maps it’s very easy to get distortion along UV seams particularly where two hard edges on a model meet.  This generally isn’t an issue with more organic-like models like characters where the model has all it’s UV seams hidden at the back and typically share 1 smoothing group.  The most challenging scenario is when you want to take a low poly model that has hard edges and project smooth edges onto that.  There are a number of methods of going about trying to achieve this,  some people suggest chamfering edges to make the hard edge of the low poly model smoother but the drawback for this is increased poly count (by a fair amount).  The other common way to do it is to separate hard surfaces in both UV layout as well as smoothing groups, so your smoothing group edge borders/seams should match the UV seams.  This page outlines this in more detail:

https://80.lv/articles/best-practices-for-hard-surface-normal-map-baking/

 

So this is why the goldeneye helicopter has been taking me so long,  I expected to have it done by now but running into these issues stalled me in my tracks because I just couldn’t move on without some answers.  One thing I’ve started to get a better idea of is the idea that models with rounded edges need to have those edges exaggerated quite a bit in order to make a nice bake.  It ultimately comes down to pixels,  with an exaggerated edge the bake has more room to pack information into pixels in the normal map.

 

Another thing I’ve learned the hard way, is normal maps don’t like symmetry modifiers too much, I used symmetry for the UV layout of the helicopter to try and save on space and have increased resolution in the texture maps.  Once I brought the model into VP however it’s obvious the lighting is acting differently on one half of the model since it’s being mirrored, in VP it shows a harsh line down the center and lighting is not even across the center symmetry line.  So for VP at least I would recommend not using symmetry for UV layouts if you’re planning to use a normal map.  The model will look fine with symmetry so long as it doesn’t have a normal map.

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