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Things to watch for when making AUTOTOPO curves?

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So, when the dialog box for AUTOTOPO pops up it admonishes one to avoid things like crossing curves and having curves too close together. Yet, when I watched the related video featuring the rat character the author (after showing various methods that don't work) shows using many, many splines that cross each other in multiple places, and they are numerous and placed close together.


Which approach is preferred?


I tried an auto test on this dragon model I imported from Lightwave and got some ugly topology. Then I tried defining more numerous and precise splines, including many that crossed as the rat video said I should, and after nearly five hours of calculating (I started it and left to do stuff elsewhere) I came home to find it still unresponsive and had to force quit the app.


Some insights, please? Many thanks in advance!

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The rat tutorial is very old and is outdated on how to use the auto-retopo routine. Go by the current guidelines for setting your curves. Start with a few and then add more if needed. After working with the routine for awhile through various models, you will start to know when and where to put them darn curves at...  :dash2:


The auto-retopo routine stills needs some polishing but it can be workable...


The below is my method but you of course might find your own method that works and it also depends upon a per model basis.


I do not know if your model is a voxel or surface mode model so I will give the tips below.


My own preference is not to run the routine on a surface mode model as it is possible in your sculpting that interior holes were created. If you know your model is clean, then it should be no problem. 


I clone the model and the switch to voxel mode. I am here not worrying about capturing all the fine details when switching over to voxels but getting enough resolution to least least capture the main shapes or medium details. If you have very thin areas of the model then give plenty voxel resolution in that case. The routine runs better if thin areas have lots of voxel resolution.

Hide the surface model object. Do now worry here. You will be using the surface mode object for the baking.


Under the Vox Tree tab, in voxel mode run close holes.. If there are any interior holes in the model they will be filled. Interior holes will play havoc with the auto-retopo routine and the routine might never compete, just keep running.

CaptureDetails--- very important... If you have a lot of noise detail on your model set it lower as you just want to catch the main shape of the model. look at my setting in the attached image which is 25.

I find 1.2 on the Auto-Density seems to work best in a number of situations.


Decimate model can be left at 40 to 60, the higher the number the longer the calculation and might not get any better results but you can test...

Smooth Resulting Mesh Tangentially, Your call... I will keep it off a lot of times, just do what works best for your model.

If your model is symmetrical be sure to turn symmetry on.

If you paint any density on the model, I set my number to 5 but that is what I feel works best, your mileage may differ.


Run the routine and see what you get. My model had no guides. If it looks good, great.

If not start with adding a few guide strokes, follow topology. Paint some density if needed.


Once you are done getting your low polygon retopo mesh, hide the voxel model and unhide the surface mode model with all the fine details.

Now you are ready to create your uv seams and uv set and bake.


Last Note :The calculation on the routine runs fairly quickly but if it is taking a long time then something is wrong.


Nothing beats manual retopoing and more so for animation. Do expect some spiral loops, they are a lot less now but you will still get some. I hope that the 3DC development team will fine tune the auto-retopo routine at some point.

Last image is the baked normal map. image quality is a little low because of the jpg compression.

Opps forgot to add the auto-retopo baking panel. corrected now.

I know this was a long read but some important tips needed sharing... I hope this helps you to obtain a better auto-retopo mesh...




Edited by digman
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Most excellent advice, and long is good when information is involved!  :yes:


Heading out to the gym but when I get back later this morning I shall follow your workflow and see what I can come up with. I understand and agree that manual retopo is always going to yield more animation-friendly results, my main agenda here is to see how close I can get with auto first and then delete the high detail areas and do them manually. Just want to leverage the auto to speed up the low-deformation portions of the new mesh. I like working out new techniques, it's part of what makes this job fun!  :moil:

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"I like working out new techniques, it's part of what makes this job fun!"   :moil:

Ah, you are a digger also... That is reason for my name Digman... :)


Jurassic Park--- Hammond is a digger like me!, said the miner to the lawyer..


EDIT: In my first post I stated "Close holes" I should have said "Fill Voids". It was late when I wrote the post.

Edited by digman

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To go with the above postings.

Another model... bake to the paint room for a normal map... 8200 polygons.

Non symmetrical and no guide strokes...

Same auto-retopo settings as the first model shown in post.

Last attached image from the sculpt room.



Edited by digman

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Post "4" I hope you do no mind me throwing more into your thread... 

The thread sparked my interest in testing some more using auto-retopo...


It appears with thin objects that surface mode works better at least in some cases so far in my limited testing. The vertices do not snap to the wrong areas of the mesh.

The model needs to be clean with no interior holes / voids or mesh intersections.

Same settings as before but less polygons, appox 2000

Attached image shows the baked normal mapped model.


Edited by digman

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Post 5 and final...


43,000 retopo mesh, sculpt was a 6 million polygon scan. I felt this was more of a complicated mesh for the routine to work on. A few problems at the hooves, my fault there and some on top of the hat. I just did not fix them.

I add to cut off the reins and stirrups but those can be modeled back in and made a separate mesh. Plus I cut off the stand which can have it's own separate retopo mesh.

I am almost enjoying auto-retopo now...  ;)


Attached images.

The sculpt

The auto-retopo mesh

The normal map with one of Riddels fine wood PBR materials.


And if you missed this in my many post... 

EDIT: In my first post I stated "Close holes" I should have said "Fill Voids". It was late when I wrote the post.

Sorry about writing the wrong words there... 




Edited by digman

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David, do I understand, no curves were drawn by you? The mesh looks great and the repairs would be simple. I've had good results with reducing the polygons.

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Cool stuff! 


I went back to my original Lightwave model and made a fresh start importing into 3DC, sculpting and then trying AUTOPO.  In the course of my experiments I found numerous places where the original model could be better, and I made some bad decisions in the original export that also came out during sculpting. With lessons learned this one came in much cleaner.  Here are some screenshots.


Sculpted model:



My AUTOPO settings:



The focus shading I used:




The first AUTOPO run, no guide splines:




I decided it could be a lot better so I added some guide splines:




And this was the result with guides:




Still needs a ton of cleanup but with the guides the flow around the head and limb joints started out much better which will make blending in the manual retopo stuff easier once I've ripped out the problem areas.


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@ tony... no guides as this was just used as a static model and I had enough polygons to cover the all areas. This helped in the areas where the polygons are going somewhat counter to the edge flow. All in all for the more complicated model, it did a decent major edge flow job. The model would be fine for a static render. I also put some guide strokes in later but have not shown a screen shot of that one. I still am testing to further improve my autopo skills.    

I ran the model at 10,000 polygons too but did not post that one. That model was decent as well.


What I appear to be finding is that the "Capture Details" appears to be an important setting for better edge flow. There seems to be sweet spot depending upon the model. Too high of a number the more the routine gets caught up in trying to capture many details and loses in the edge flow area... Too low of a number you get overall coverage but the edge flow here again loses.  


The mongol stature has 39,000 polygons... Autopo setting was "capture details' set at 20 and decimate set at 35. Auto density set at 1.2. The auto retopo came out pretty darn good. No guides, but that is only because of what testing parameters atm I am using.

His face not so plus a few small areas need a little help but there were other larger details the routine was going for based upon my settings. That is ok, I can fix the face and the other few areas easy and then it is baking and fun time in the paint room. 


@SpinLand... Ya getting the hang of it :) ...Running the model at times without guides first, gives you the areas where the edge flow needs help. One of the reasons I do it but not all the time.


Edited by digman

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Yeah, I think I'm starting to get a feel for how 3D Coat does stuff. Besides the dragon sculpt I'm also working on a gargoyle character. I built this guy in Lightwave as well and am adding him to my list of projects for doing sculpt work on. Like the dragon, the wings are already built but the structures are straightforward and there was no reason to do any sculpting on them. I'll just stitch them onto the retopo meshes before I UV map the models and start painting the diffuse and normal maps.






Here's my start on doing the manual retopo of the face. A few false starts here and there as I get used to the workflow but I'm starting to get into a groove.




Both of these characters are going to be featured in some animated shorts so I need to make sure they're ready to rig and that they deform well.


This is a quick test run of part of the short the gargoyle will be in, using a low-res proxy model for now.



Edited by Spinland

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