Dont reinvent the wheel -- A quick method for shrink wrapping pre-made body parts to hi-res meshes
grand marshal polycounter
I am sure this is not a novel technique, but I haven't seen it described anywhere so I thought I would share.
How I came up with the technique:
After working on retopology for the first time, I found the process to be egregiously time consuming. Probably the biggest reason is because I am not very good at rerouting topology and thus spend a lot of time chasing down n-gons and triangles...anyway, I spent a lot of time doing trial and error with the shrink wrap deformer in Maya trying to speed up the process for the hands.
First I tried just shrinking cyclinders onto the fingers, but then I still had to use quad draw to connect up the hands. I imagine a pro modeler could do this with their eyes closed, but even that will still take a bit of time. Finally, after looking around online for references of clean hand topology (and not just clean, but well set-up for animation too), I realized that there was probably hundreds of models, many for free, that I could simply just download and use. Somebody else has already done the hard work, why reinvent the wheel, right?
But, of course, these generic models won't fit yours just exactly. It's just that nice topology you want to apply to your model. So here is how I did that.
The Technique (Maya 2018):
Bring your low-poly, premade hand model (or whichever part you are doing) into your scene. You can either make that yourself and save it to a library, or you can probably find one online depending on what it is.
To get it front and center on the hi-res mesh you'll be copying it to, have the move tool engaged (press W), hold V, and wiggle the cursor over any vertices on the high res mesh. Your currently selected object will snap to that point.
Rotate, scale, and then roughly adjust your lo-poly model so that it is lined up with the hi-res as much as possible.
Now comes some tedium, but it is not near as much as drawing a hand from scratch. You are going to have to move points around, but you don't need to do any thinking whatsoever so you can just turn some music on, relax, and get this part done. What you need to do is adjust the vertices on the low poly so that it is just a bit larger than the hi-res mesh. Try to make the low-poly mesh fit over the hi-poly mesh like a glove. If you are working on something like the human hand, this will involve a lot of camera rotating, working in wireframe view, and getting really close.
Refer to the picture below. As you can see, on all but the pointer finger I have adjusted the vertices so that the lo-poly hand sits over the hi-poly hand like a glove. Took me about 15 minutes. Try using soft-select at first to make big adjustments, then go back and fine tune individual vertices.
Now, select the hi-res mesh, and press the small magnet icon up on the toolbar to make it live. It will become green like in the picture below. If you aren't familiar with this, please google it and read the documentation. In a nutshell, a live object is, like the icon suggest, magnetic, and makes things stick to it.
Now, select your low poly mesh via object selection, not component, and press quad-draw tool. This will turn it blue, like you see in the picture below. Now, simply hold down shift which engages the smooth function, and run your cursor over the mesh. The vertices will snap onto the hi res mesh underneath. Wah-la!
You are likely to encounter a few small problems. If you have vertices very close together, like one finger adjacent to another, they may jump to the wrong finger. Simply grab that individual vertex and pull it back into place.
I don't think this is the fastest technique for all parts of the retopology, but it sure has saved me a lot of frustration for the hands. Of course, this is cheating in a way, and I think a good modeler should know how to route topology with their eyes closed, but if you are eager to get through these tedious parts and onto the fun stuff like painting your model, I hope this might help you.
How I came up with the technique:
After working on retopology for the first time, I found the process to be egregiously time consuming. Probably the biggest reason is because I am not very good at rerouting topology and thus spend a lot of time chasing down n-gons and triangles...anyway, I spent a lot of time doing trial and error with the shrink wrap deformer in Maya trying to speed up the process for the hands.
First I tried just shrinking cyclinders onto the fingers, but then I still had to use quad draw to connect up the hands. I imagine a pro modeler could do this with their eyes closed, but even that will still take a bit of time. Finally, after looking around online for references of clean hand topology (and not just clean, but well set-up for animation too), I realized that there was probably hundreds of models, many for free, that I could simply just download and use. Somebody else has already done the hard work, why reinvent the wheel, right?
But, of course, these generic models won't fit yours just exactly. It's just that nice topology you want to apply to your model. So here is how I did that.
The Technique (Maya 2018):
Bring your low-poly, premade hand model (or whichever part you are doing) into your scene. You can either make that yourself and save it to a library, or you can probably find one online depending on what it is.
To get it front and center on the hi-res mesh you'll be copying it to, have the move tool engaged (press W), hold V, and wiggle the cursor over any vertices on the high res mesh. Your currently selected object will snap to that point.
Rotate, scale, and then roughly adjust your lo-poly model so that it is lined up with the hi-res as much as possible.
Now comes some tedium, but it is not near as much as drawing a hand from scratch. You are going to have to move points around, but you don't need to do any thinking whatsoever so you can just turn some music on, relax, and get this part done. What you need to do is adjust the vertices on the low poly so that it is just a bit larger than the hi-res mesh. Try to make the low-poly mesh fit over the hi-poly mesh like a glove. If you are working on something like the human hand, this will involve a lot of camera rotating, working in wireframe view, and getting really close.
Refer to the picture below. As you can see, on all but the pointer finger I have adjusted the vertices so that the lo-poly hand sits over the hi-poly hand like a glove. Took me about 15 minutes. Try using soft-select at first to make big adjustments, then go back and fine tune individual vertices.
Now, select the hi-res mesh, and press the small magnet icon up on the toolbar to make it live. It will become green like in the picture below. If you aren't familiar with this, please google it and read the documentation. In a nutshell, a live object is, like the icon suggest, magnetic, and makes things stick to it.
Now, select your low poly mesh via object selection, not component, and press quad-draw tool. This will turn it blue, like you see in the picture below. Now, simply hold down shift which engages the smooth function, and run your cursor over the mesh. The vertices will snap onto the hi res mesh underneath. Wah-la!
You are likely to encounter a few small problems. If you have vertices very close together, like one finger adjacent to another, they may jump to the wrong finger. Simply grab that individual vertex and pull it back into place.
I don't think this is the fastest technique for all parts of the retopology, but it sure has saved me a lot of frustration for the hands. Of course, this is cheating in a way, and I think a good modeler should know how to route topology with their eyes closed, but if you are eager to get through these tedious parts and onto the fun stuff like painting your model, I hope this might help you.
Replies
I have a question: if you're going to work on the entire low-poly to refit it to the hi-res, why do you need the hi-res at all?
Wouldn't it save time if, instead of creating a hi-res to shrinkwrap to, you just reformed the low poly directly to whatever body type you're going for? (Using sculpting tools, soft selection etc. on the low poly)