(Noob) Baking High Poly Normal Map to Low Poly Normal Map

Devon M

Hello everyone. I spent my spring break learning zBrush and xNormal. I did a tutorial and I *thought* I understood how to do this. Clearly, something is happening. So here is my problem.

I made a high poly sculpt in zBrush approximately 1 million polys. I duplicated it, and decimated it to 248 polys. I now have a high poly and low poly mesh. In zBrush, I UV'd the high poly mesh by polygroup (it became one single UV mesh). I export them both, put them in Maya. I then UV map my low poly mesh and get it nicely in a 0-1 UV space. I export them both. I bring up xNormal and place the high poly in the high poly section, and the same for my low poly. I select to bake out only a normal map, and this is the result.

http://puu.sh/o2Hie/0b8465adc4.jpg

Here is a picture of the UV of my low poly mesh.

http://puu.sh/o2Hk2/827a7c918e.png

Here is a screenshot of the low poly and high poly together.

http://puu.sh/o2HlV/94488725b0.png
http://puu.sh/o2Hpq/be0faca040.jpg

Now, the only thing I can think would be a problem would be that my high poly and low poly meshes UV's are different. Other than that, I'm kind of clueless. Like the topic stated, I'm a noob =P This is my first time doing something in zBrush that didn't involve a tutorial, so I really hope you guys can enlighten and teach me something to help me improve. Thank you all for taking the time to look at this.

Bartalon

The high poly does not have to be UV mapped to bake a normal map.  There are very few situations where you will ever need to UV map a high poly mesh.  A normal map is a 2D representation of the high poly's physical surface curvature in relation to your low poly's surface curvature and vertex tangents baked into the UVs of your low poly's UVs only.

My guess is your high poly and low poly are not occupying the same physical space when xnormal goes to bake maps.  Be sure when you export your models from Maya, they are both sitting right on top of each other with the pivot set at origin (0,0,0 XYZ) and you have the transformations frozen (Modify > Freeze Transformations).

Additionally, to get a correct normal bake, certain rules must be followed.  The short version is to set hard edges where you have UV seams and soft edges everywhere else (it really depends on how you are baking your maps, but this isn't a bad place to start).  The long version, which is seriously recommended you read in order to understand/solve normal baking problems, is here: http://polycount.com/discussion/107196/youre-making-me-hard-making-sense-of-hard-edges-uvs-normal-maps-and-vertex-counts#latest

Scruples

Highpoly doesn't need UV's, lowpoly UV's have more seams than necessary and it's little space inefficient but should be fine. Are your models overlapping correctly, check by using xnormals 3d viewer. You mentioned that you haven't looked at any tutorials, the internet is littered with them, please watch/read some,
here's one.
https://www.youtube.com/watch?v=jq_3URQjYxs

Devon M

@Bartalon: Thank you for the suggestions, I'll check all of that. 

@Scruples I must have worded it incorrectly. What I meant to say is I have done tutorials for this already and I thought I understood what I was doing because I completed the tutorial just fine. I thought I could apply those same ideas on my own project without the help of the videos. But I ran into these problems. Thank you so much for your suggestions. I'll look into them right now. 

I'll respond if I figure it out or not. Thank you both so much. 

Devon M

@Bartalon and @Scruples thank you both. I read the forum thread you linked me and watched the video on page one. I also watched the video you posted here, Scruples. Once I deleted type history, placed both meshes on top of each other, froze transformations, center'd pivots, my normals came through. 

Thank you both so much and for the advice. I especially didn't know about not having to UV the high poly mesh. 

musashidan

Devon M said:

 I especially didn't know about not having to UV the high poly mesh. 

Best to find out on your first bake rather than in 2 years time.... As has been mentioned the sole purpose of the high-poly is to capture its details.

Devon M

@musashidan Thank you for the sound advice sir! I've been sculpting more models today and so far it's been smooth sailing.