Coincident faces mess up normal map?

scourgewarper

I am currently working through 3d palaces awesome ED209 tutorial (hope its ok to say that) however i'm at the normal mapping stage and am getting a lot of normal map errors.

To brush up I've been reading through the normal mapping sticky and there was one point brought up - when baking your normal maps in max (I'm using 2009) make sure there are no coincident faces between your hi and low poly models?!?

My understanding was this was irrelevant; as long as your projection cage encompassed the high poly model with no intersections then your normal map should be ok all things considered (depending on model complexity/recess considerations etc)

I can post up the shots of the errors if required but suffice to say this is happening on a relatively simple 64 poly toe piece of ED although I did notice that many of the faces of the high and low poly are flush to each other. The fella on the normal mapping thread recommended adding a push modifier and applying a tiny 0.001 amount to your high poly model which I did and then I got an all black render :S

Any advice?

Ott

Show us what you are trying to bake, with your low and high. I'm confused what you are talking about exactly. The idea behind putting a Push modifier is so that you ensure that your low is under your high, but I'm not sure why you would be getting black renders.

make sure there are no coincident faces between your hi and low poly models

I'm lost on this statement.

Ott

Oh, sorry....it's the English teaching me English...I was lost on the use of the word coincident :P

I presume he means "occupying the same space", and technically you can get away with it. The normal projections go up AND down to a certain amount, but the safest bet is to always have the low just under the high....(even though this isn't always feasible or possible.)

I've been told that adjusting the "Height Map" Min and Max values in the Projection options is the amount of leeway you have with the actual cage detection distances up or down, but if I am way under or over the high poly, ill add geometry to the low to fix it.

scourgewarper

Yer sorry probably should have made it clearer I meant that many of the polygons of my high and low poly model occupied exactly the same space creating that quirky artifact where they are both competing to be rendered in the viewport.

I was trying to actually hide the low poly or make it non-renderable during the bake to avoid the normal map errors but that didn't work. I'll have a play around with the min and max values in the projection options and see if that works cheers mate.

pior

Low and High being at the same point in space shouldn't cause any issues. The problem lies elsewhere, most likely in the render settings, or maybe a bug in the renderers engine itself (ala mentalray black AO spots where the lowpoly shows through)

(I have succesfully baked a lowpoly normals to themselves without any artifacts recently)

Hope this helps!

MoP

Yeah, there shouldn't be any issues if your high/low are in exactly the same plane, overlapping each other. That should still bake fine.