[Solve] How the Uv follow the object's shape and no stretching

shinakz

Hi, I have some question about uv here.
I wanna make the uv same as the camera show and not overlaping


So I cuts the uv edge and try to maintain the shape same as object and no overlap like this.


But when I use checker to check the texture is stretch too much, is anyone have some idea how to fix?


Btw, I'm using Maya.

Eric Chadwick

Why do you want the UV to match the camera? And why no overlaps?

musashidan

You can use camera projection mapping.

shinakz

Actually I’m doing internship in a small company, and there have no 3D artist. I was require to do this but my 3D skill still not a professional and I have no one can ask on company. I hope can at least get some advise in here

musashidan

What are you trying to do? Is this for a still render?

shinakz

I’m doing the model for AR Color book. User can color on the picture and use an apps to show in AR 3D. They said user color actually is doing texture, color on its UV, so the UV next to same as the picture / camera show.

Obscura

I don't think you need to hand make such uvs. A shader can be made that uses the screen coordinates to do this kind of projection. In theory, you don't even need uvs. Or maybe I misunderstand what you are trying to do. 

Once I made a mesh painter application and you could paint the mesh just like in any 3d texturing software. In my case, I needed regular uv map with no overlappings. 

But maybe your thing is totally different from how I imagine it.

I would assume that you can turn and go around the projected ar mesh right? in that case you would need normal uv layout. Because otherwise the back faces would be badly textured.

shinakz

https://m.youtube.com/watch?v=32lQxcIjxMU
Im doing something as this video show.

This guys is using 3DS and I using Maya so I’m not sure the UV editor is the same or not. And I see this guys doing no stretching but he skip the uv part so I not sure how to do with no stretching. 

Obscura

Okay I see now. Aaand. You are actually doing it right. don't put a checkerboard on it. Just try to make a snapshot from the uvmap, or make a render from the projection camera, and paint over it. You will see that it works like in his example. And yes, other than the camera angle which was used for the uvmap, it will definitely show stretchings. This is why I was asking if you can rotate the target mesh in the painting app. Because then only that certain camera angle will show it "correctly". It is correct otherwise too, it just doesn't look any good.

And actually he shows the full uv process in the video even though he does it really badly. He makes a snapshot from the viewport, puts that into the uv editor and hand aligns the vertices. This is just bad. I'm pretty sure it can be done with a few clicks, just like you did in maya.

shinakz

I'm doing like that but my boss said the user probably will draw a door or something on it so don't do it with stretching and use checker to check.

And actually I'm quite new in maya, so I also follow the video and do it with hand aligns. Can I know if there have a way to speed up my work on it uv?

Obscura

Have you actually tried painting over your uvmap?  About the better way - i typed maya camera projected uvs into google and the first link was a tutorial about the process. 

shinakz

I had try to draw something on uvmap make sure it doesn’t look stretched, but some part is still stretching and I’m not sure how to fix.

musashidan

That workflow the guy is using in the link is terrible. As I said in my first post, look into camera projection. It's what it's used for in VFX/matte painting. I don't know much about AR colouring, but I assume you can rotate and colour in 360?

The guy in the video is basically trying to do manually what camera projection will do with a few clicks. It will project your 2d image in world space based on the camera angle.

shinakz

If I use camera projection uv won't it overlap when color on texture?

Obscura

Jesus... There is no way to do this without overlapping. If it can be seen only from one angle in ar, overlapping isnt a problem. If it can be rotated, or it turns based on your view, it is a problem, and then you should just do a regular uvmap with no overlapping. The guys uvmap in the video was overlapping too though. 

Obscura

I think its about time for you to properly research how does this coloring book tech works in the reality. Because if it simply paints by taking the uv coordinates under the pen,finger, or whatever, then technically any uvmap would work more or less. And i have a feeling that it does what i described. This would save all of us from the headache including yourself.

Alex_J

I think this is an issue of lacking fundamental knowledge of the common methods for UV mapping, and thus any answer given will likely go over-the-head. It's no fun, but sometimes you just got to go back, hit the books (i.e. read the manual, video tutorials, archived threads and articles, etc), and take all the time necessary to build a breadth of knowledge about the subject, starting at the very basics. Even if you believe you're past that.

Every time I have done this in my own learning, I end up learning a boatload more than just what I intended, and this ends up multiplying my technicals and exploding my confidences. Big time. 

So, TL:DR, it seems like you need to get a better understanding of how UV's work at the fundamental level. Most likely some review is going to enable you to come up with your own answer much faster than even a team of top level Polycount scientist can by poking the details out of you. Check out the wiki!

shinakz

Ya, I’m not really know so much about the uv since my college also didn’t teach too much about it. I try to do some research on internet and watch the tutorial video, but mostly is is teaching unfold, I learned it but isn’t what I want in doing this project.

But, yea you’re right, finally I come out answer with my own. Even tho, I need to thanks everyone who willing to reply this post and  helping me, give me advise in doing this. Thank you everyone.

musashidan

Here is a Disney research paper on the subject from 2015, and the techniques they used to make this work. They used a fully unwrapped mesh and a lookup map that matches pixels based on UV regions and fills in the areas of the mesh that don't exist in the 2D colouring book image. Might be worth a read. Good luck.

https://www.disneyresearch.com/publication/live-texturing-of-augmented-reality-characters/