I have been messing with this tire all night. No matter what of projection I use. I will not produce the normal map of the tire correctly. Ive attached a screenshot. I've moved the the original tire beside the low poly one, so you can see the type of tread it should be and on the right in my uvw editor, you can see the normal map it produces.

does anyone have any idea why this happening.

www.billa1.com/images/pics/tire_screen.jpg

Did you reset your cage first and then adjust it to incumpus the high rez tire?

Thanks for replying, yeah i did, after looking at it more closely, it seems the normal was producing the rest of the tire, it just wasn't as detailed as I had hoped

It looks like the details you have on the tire are almost at an exact 90degree of the surface. And since said details are marked with a mere hard edge (smoothing groups/split normals), it won't show at all. You can try running a relax on all your verts, or bevel all your edges altogether. Faces parallel to the projection plane will now be at an angle, thus showing on the normal map (normal map = 'angle map')

[edit] By the way! How did you model that tire? Using some sort of radial symmetry technique?

Hi Pior,

Thanks for the help, but I may be coming back to you on that becuase that pretty much went right over my head.

for the high poly model, i chose one strip of the tread that I knew I could tile, modeled it completely, from one side to the other. the arrayed that object 85 times. attached all of them together and welded the verts.Then just applied a bend modifier. If you want to see some images of the process let me know.

High poly modeling has never been my problem, its this god-forsaken low poly modeling that im struggling with

Thanks again for the help

edit, I read that again, You mean i need to bevel all my edges on the high detail car. Jesus that will take a while

I think what Poir is getting at is that, the edges themselves don't have much to define them from the rest of the shape when you take a straight-on shot (what RTT does) of the tread there isn't much of a chance that it will pick up the inner sides of the tread. So it looks like one smooth surface. The only real reason you see the tread now is because you've moved the camera off to the side.

If you beveled the edges there would be a tiny bit more detail that might make it into the normal map. You can also angle the "walls" of the trenches in thread so they stand a better chance of being captured by RTT when it takes it straight on shot. Which I think Bevel/relax should do the job, of giving you more edge detail and angling the walls.

Also, a lot of the tread detail looks like its smaller then one pixel on the actual map? Which will give you problems because it will have to choose. Considering its a 2048 I'm not sure you want to increase it much higher, so I think you should think about exaggerating the tread detail a bit.

Personally I would un-bend the tire, make the changes, and render it as flat geo. It would help minimize the minor cage issues that sometimes pop up when rendering round objects. I would probably relay more on the diffuse texture with quite a bit of AO to sell the tread. But then you have to ask, how important is it really to see the tread? Is it really worth a 2048 or where you just trying to get a higher pixel density?

Or just paint the normal by hand...

For some pics that explain the issue, see section 4. of this tutorial:
Modeling High/Low Poly Models for Next Gen Games by João Costa

More info in the wiki, if it helps.
http://wiki.polycount.net/Normal_Map

when you make a normal map you can't really have 90 degree things you have to angle the edges so the projection can see them ie.. "\_/" NOT "|_|"

ah ok I see now, thanks for explaining that guys

I quick way to deal with this is to just use one strip before you rotated it 85 times and just bevel everything there. Another way to deal with this is to place the hi res as a flat strip like is you were unwraping and texturing. The clone it so you have enough of the pattern, then bake.

Alex

Wow, that's cleared up a lot of the questions I've had about how people get such good normal maps when mine would lose a lot of details. Thanks guys.

Thank you Sage