Normal Map Issue (Details appear 'slanted')

szhafri

Hi
Im having some Normal map issues that has been happening to me for quite sometime now. This is regarding baking normal maps form high poly to low poly. Basically my issue is that most of the time when i bake my normals from high to low poly , some of the details will appear 'slanted'. For example, a screw that's suppose to face upwards is now facing sideways.

Here are some screenshots of my issue:

As you can see, the red circle is the screws that is not facing up for some reason.







This is the model(white: high poly/ black :low poly)


As u can see the screws lighting are off.




Any reason on why is this happening ? The only light source that I use is skylight.

I can provide few additional screenshots from my other models .but basically all my normal map issue is similar to this. usually on small details.

PS: im using 3dsmax

Cheers,
Zhaf

myles

Hey Zhaf, this issue is to do with your lowpoly not having the supporting edges for the tangents projecting the cage to hit the screws properly. Personally I don't think its such a big deal, but a good way to fix it on this occasion is to just add a single vertex in the center of each screw to allow the projection to hit the screw from the right direction.

I know your not looking for feedback on this, but I suggest you increase the smoothness of the edges so the normal map picks it up better, also increasing the padding would be advisable.

mLichy

nevermind...

Joshua Stubbles

Yep, you need more supporting geometry on the edges in order for the tangents to align with those straight floater details, OR, you need to use different smoothing groups on those surfaces, in order to break the tangent and have it align with the flat face. Keep in mind, if you break that with a smoothing group, you'll need to break that edge in the UV map, or you'll get a normal seam. The problem with adding the edges with a chamfer would be that the long, thin triangles are tough on renderers.

Next

hi there!
As myles mentioned the face normal interpolation of the rays are not straight at the bolts thus they are baked wrong and have somekind of angular view in the normalmap.
there are more less 2 ways to deal with it.
1 add bevel to the edges at the sides where the wrong direction is.
2 bake with an actual geometry cage of your lowpoly and adjust it so the rays to the sides of the gun project normal to the surface of the bolts.
...and 3 you can optimize solution 2 by adding different smoothing groups to the top bottom and side faces of the lowpoly gun and split the uvs according to this and bake then.
3 gives best results quality-wise but smoothing groups and split uvs will increase the actual triangle count on the graphics card....which is not so important in your case i guess.

before i forget:http://wiki.polycount.com/NormalMap?highlight=%28%5CbCategoryTexturing%5Cb%29 ...very useful info ! Read it if you havnt.

cheers

szhafri

Thx for the reply guys! Will try them out and will keep u guys updated on this.

Mark Dygert

The issues can be seen visually if you turn on cage display in the projection modifier and turn on "point to point". It will show you the angle of the ray projection at each vertex. You can also tweak these points to get better angles (which impacts other areas so do it carefully).

More than likely your cage is going around a sharp angle and the rays are doing their best to project around it. Like others have said you can:
- Add supporting geometry to help ease the ray projection around the corner and straighten them out so the rays aren't skewed over the bolts.
- Adjust the points on the cage so they straighten out the rays over that section, probably heavily skewing the rays in other places.
- Bake the bolts separately with just a plane, then combine that in your normal map manually.

Either way turning on point to point will help you work out the best possible solution since it helps visually explain the angle of the ray projection.