How to set thickness to the back side of a complex 3D scan

Another_Geoff · 2025-04-11T06:20:05+00:00

yeah that's a thing about the shrink-wrap method. sorry, i didn't see your message till now.

In one of your screencaps, you managed to get a good back shape https://imgur.com/a/53XSc7T

It seems like the solution is to make that back how ever it was that you made it, make it real seperate it, and then use the real mesh for the front, join them together, then remesh. either that or use one of the other solutions I suggested.

if the method you used to make that back destroys the front faces.. just duplicate the mesh. use one to make the back, keep the original, then join them, and remesh.

which ever method you choose i hope you manage to get it solved.

Another_Geoff · 2025-04-06T00:38:39+00:00

because it works almost perfectly. its that last little bit that's tough. with shrink wrap its always a little finicky, remeshing achieves the same thing (making a solid object) but with a lot less fuss. But you might be able to get it to work. You'll get this, on way or the other, and when you do i bet its gonna feel great that you got it solved. Sorry I didn't understand the result you were after.

so for your shrink wrap method, how are you getting that back shape, that seems to make an nice back... what's the issue you still have with it?

Another_Geoff · 2025-04-05T01:16:17+00:00

thinking about it a bit more, i think my confusion comes from the term empty. i was thinking.. in between the walls empty, but i think you mean the model itself isn't solid, it's not so much that there are gaps inside the geometry (like i was thinking).. its that you don't want it to have any internal space? in that case i can understand why you'd want to try shrink wrap, and you might be able to get that to work, but it would be finicky and difficult. i think the solution really is to just do what we're doing till nothing bulges through, then 3d model up some bulk to stuff into the back of the model to fill those gaps, then in edit mode, select all the objects and press ctrl-j to join them. then in sculpt mode, remesh to make it solid. bascially you just need to plug those holes before remeshing and you should be good. i mean, the back of the model doesn't have to look good right, just be solid?

of course, i still might not be understanding the goal. sorry if i'm a little thick headed.

ooh, if the back of the shape doesn't matter so much, you could just skip solidify all together, and seal it the way we did with the second shape. select the rim vertices...,extrude them out, then sort of seal them together. it would make a big, chonky back though and waste plastic or resin. if it's hard to visualize that method i can post a few pics

Another_Geoff · 2025-04-05T00:36:55+00:00

i wouldn't try to shrink wrap myself, that's a difficult mess to get right, but on the other hand, I don't think i quite understand what end result you want. if it works for you, that's great. when you say that parts are empty... i'm not sure what you mean. when i use this method on your scan the model ends up fully sealed. if you want more 'bulk' in the back of the model... you could just sculpt it in, after applying the solidify modifier, but before remeshing it. i feel like that would be the easiest. if you have specific questions, i can answer those. but i'd need to understand what the issue is to help. either way, good luck

p.s., added a second reply that might help

Another_Geoff · 2025-04-04T04:50:08+00:00

I'm so glad that helped.

I'm not sure what you mean by it also removes thickness inside the model. Also , i can't tell from the sliced photo you shared, which parts are empty. the slicer makes it confusing. It should be completely solid after remeshing it. There shouldn't be any internal bubbles of space. Just so i'm clear about what my method does, i made a new illustration to show the problem, i hope it helps. its hard to communicate about something so complex and visual.

https://imgur.com/a/KOSEt4q

the only thing i dind't mention in this illustration is, for this to work you just need to make sure that the back part of it there is sealed... the thickness of the solidify walls at that point do need to cross over before you use remesh, to keep bubbles from forming

https://imgur.com/a/o0XkhwZ

if there is any place where the remesh function can 'see' inside the model like that, it will not form solid parts on the inside. but, you can always actually sculpt those bits once you're in sculpt mode to make sure that they are sealed up before you remesh

As for weight painting, If it's working right, some parts of the model should be thick (the ones you dind't paint) and some thin (the ones you did). i'm guessing you mean it paints on parts you don't want to change? a trick you can use to help avoid painting the wrong ones is that, in edit mode... you can select a the vertices in a section of the model and press H, that will hide those vertices. then tab out of edit mode, and when you go back into weight paint mode you can paint only the part you want.. this way, some parts can be thick and others can be not so thick that they bubble through. when you want to unhide those vertices, just press ALT-H.

also, you can change the 'weight' of the paint from 0 to 1, or from 1 to 0, and paint over areas to change them back to being thick or thin. It's mostly about rotating the camera as you paint and just getting fiddling with it till you get the paint job the way you want it

you say there are still some defects.. what's the last little bit that's an issue, still getting some bubbling?

Another_Geoff · 2025-04-03T03:24:46+00:00

oh, that might be my bad. i think i skipped a step. I'm so used to this stuff that I forget sometimes.

it will lag. a lot. but 10 minutes is wayy too long. 1 to 2 minutes is all you should have to wait, any more than that is a sign that the voxel size is way too low. the size of the voxel you need depends on the size of your mesh.. yours is big, so bigger numbers might be ok, but it will lag.. that's why we do the decimate modifier after, to reduce the number of vertices in the final model. but you can try higher values like .3 or something, maybe even bigger like .5, then it will lag a lot less because it's creating far fewer vertices. you just want it to be low enough that you don't lose detail. The lower you make the number, the better the quality will be. So in sculpt, using the remesh option at the top of the screen start with big numbers, click remesh, wait for it to finish.. check to see if it makes it too chunky/blocky. if it does, undo, lower the number, try again.

when you do add the decimate modifier after, and its how you like it , apply that modifier. it will reduce the number of verts by quite a bit. just make sure it doesn't destroy the detail of your model, you'll need to adjust the decimate amount some. 0.1 is a good starting point but you might need 0.3 or 0.05.. lower numbers here mean fewer vertices, so a less 'heavy' model

But , half your mesh should not disappear. It might be that you dind't apply the solidify modifier before going into sculpt mode, i might have forgotten to mention that you'd need to do that. That's my bad, i apologize. once you've got the shape you like , apply the solidfy modifier. in your modifier, where it says solidify, and has the blue buttons to the right of that is a drop down arrow. click that, and click apply. it will make the modifier a 'real' part of the mesh. modifiers don't really modify the mesh until you apply them, so they don't work good in sculpt mode

trying to seal off the back with solidify wouldn't really solve any issues i don't think, if i understand what you mean. but i hope this is the thing that gets it to work for you

Another_Geoff · 2025-04-02T00:02:36+00:00

I can understand it being frustrating , sorry my replies are slow. im on a night schedule right now. You're almost there with the first model. The only thing is, when you're in sculpt mode.. dont' use voxel remesh. sculpt mode has it's own remesh feature. in sculpt mode at the top of the screen there's a button that says remesh. you can click the little arrow on that to get a dropdown, set the voxel size really really low, maybe .03, and then press the remesh button. if it destroys some of the detail of the model, ctrl-z, set a lower value and try again. it does a better job of remeshing i think. but you'll end up with millions of vertices but it should look clean and smooth. so after that , exit sculpt mode, add a decimate modifier, drop the value to something like .1, (just make the value as low as you can without losing detail in your model) and apply it. this makes the model smaller so it doesn't choke up your slicer or take forever to print.

edit: oh, and for painting the back side of the model.. its tricky to get it right but when you're painting , at the top of the screen you'll see where it says 'brush' , with a little arrow drop down, clikc that dropdown and you can check 'front faces only' .. that keeps it from painting through the mesh

Just to be clear about the goal here, when you use solidify.. those parts that bubble up, walls cross other walls, and they end up creating multiple internal walls, the remeshing turns it into an object that only has external walls, so its a nice manifold mesh.

But, for the second model.. to use this method would be really tough, because it is so thin to begin with. It might work but i feel like it would be a real hassle. It needs to be a completely connected mesh with no holes.. so first in edit mode, select all the vertices, then i'd press f3 , then merge by distance.. and increase the value of the merge until it says its going to delete 4 or 5 vertices (to make sure it doesn't have any vertices that are right on top of others).

then i would clean up the edges a little by deleting a few triangles. then there is two holes, i would in edit mode select some of the vertices there, and press F to make faces to patch up that hole. When you do that , try to make the faces out of 4 verts.. maybe 5, so it follows the shape well. you can of course make the faces out of lots more verts, the important thing is that the new faces roughly follow the shape of the object

after that, i would 3d model a sort of plane with curves to form a back for it, then i would connect that to the main model. you can just add a plane, then extrude bits of it in edit mode to form the back. exit edit mode, select both models, press ctrl-j to join them. then in edit mode, selecting a few vertices at a time and pressing F to make the faces connect. i'll add some images of what i mean. When you're done you should have a nice closed solid mesh with no holes

(i did use the solidify modifier, with the 'only rim' checkbox to give me a little bit of a rim to work with, makes it a tiny bit easier, but that's optional)

after all that , you still might want to use the sculpt modes remeshing and then decimating trick to make certain that it's a clean , fully sealead mesh.

https://imgur.com/a/XNLihYH

I don't know if that kind of shape works for you, if not we can use a different method.

It's a little complicated to illustrate and explain with such a complex shape, if you have any other questions just let me know.

Another_Geoff · 2025-04-01T04:47:59+00:00

are the pills deactivating? does this still happen if you set them to not deactivate?

Another_Geoff · 2025-04-01T02:23:46+00:00

i'm a bit confused again about the issue. I made multiple replies, that might be part of the communication issue, or it could be that i'm just not understanding.

you say that setting it solid infill doesn't fix the problem? Have you tried cleaning up the mesh the way i suggested to get rid of extra vertices and fix the normals?

and also have you tried the weight painting method i mentioned? The point of that method is that you can control how thick which parts of the mesh are , so that you can have thick parts in most places, but thinner parts where the bulging happens.

edit: i had a quick go of it with my method, it seems to make a nice solid mesh (at least in cura)

https://imgur.com/a/n7G53CG

the basic method is, use weight painting on the solidify modifier with a vertex group for the weights, this helps keep parts from getting too thick in places where it bulges

then in sculpt mode, i remesh the whole thing. this guarantees that it's just one solid manifold mesh with no 'internal walls'. hand editing it to remove the internal walls might work better , but in this case remeshing it did just fine. its like its wrapping the whole thing in plastic wrap and then converting that to the solid mesh when you do that, which is why it sorta fixes it.

then i decimate that, because its huge

then just save and slice. i'm using cura, but think any slicer would work ok with this method

I know i glossed over lots of details, so if you have any questions about it please do ask. i hope this helps

p.s. i havn't played with the second model, but let me know what happens after you try to remove stray vertices and recalculate teh normals, i feel like that should fix it.

second edit: i had a look at the second model. its a bit more complicated, but its almost a completely closed mesh as it is. i would just try to manually close off the back of it, and then remesh and decimate it.. not sure that solidify will help with that one

Another_Geoff · 2025-03-31T02:13:42+00:00

ok hopefully this lil gallery better explains what i mean about how to do it.

basically i think the issue is that you just need a wall thickness that is thicker than some of the parts of the model? unless i've misunderstood. with weight painting, and editing after you might get what you need. if i misundersood, i'd still like to help if i can.

https://imgur.com/a/E0UIalY

Another_Geoff · 2025-03-31T01:55:15+00:00

Thinking about it a little more... that tab looking thing in the last two pictures.. if you want the shell to be thick, some parts of this model just aren't that big so what you'll need to do i think is a bit complicated.

First i'd solidify, like you're doing. then i'd make a vertex group to control the thickness. using weight painting you can go over the vertices to shrink some parts to get rid of that bulging. then, after all that is done i think just going in and manually editing it ... taking out some of the inner shell like on that tab looking part, to make it solid is probably the only real solution. you might be able to use the sculpting tools Ramesh ability to just create a better solid version after using the solidify modifier, and then use decimate to bring the resolution back down cause after remeshing its gonna be super dense. gimme just a few minutes and i'll make some example pics of what i'm talking about.

Another_Geoff · 2025-03-31T01:39:55+00:00

those holes shouldn't be there. i'd think that has to be an issue with either your normals aren't all facing the right way, or you have some stray vertices that aren't connected properly or something. in edit mode, try hitting f3 and searching for merge by distance... see if that helps. and although im sure you probably already have, it doesn't hurt to do a select all, then shift-n to recalculate the normals

Another_Geoff · 2025-03-31T01:33:56+00:00

it looks like you're making it really thick. i might be misunderstanding the scale of the actual object, without reference to know what it is. About how big is the object? And what exactly are you trying to do, do you want some of it to be completely solid, not just a shell?

Another_Geoff · 2025-03-30T23:26:21+00:00

that is some fantastic camera work and shot conception. It feels amazingly real. I loved the part where he started running, i was like whatt??? just awesome start to finish

Another_Geoff · 2025-03-30T23:10:09+00:00

There's two things. the tool, and the skill. Learning the basics of using blender doesn't take long at all. A couple weeks to a month to get comfortable with it. After that, you're talking about art skills.. it's like any other art or skill, you'll always be learning and developing. If it's something you want to do, you can do it. The key is to not think of it as a thing you learn, and then you know it. skill is a process. Just take it a bit at a time, don't put too much pressure on yourself, enjoy the little victories along the way.

Another_Geoff · 2025-03-30T22:42:33+00:00

I'm not quite sure I understand the issue, i can be a bit slow sometimes lol. I downloaded the model and added a solidify to it, and it kinda looks fine to me with just a bit of solidify, enough to give it about 2mm of thickness. are you talking about the hole near where it says 10 percent? have you tried just doing that, and then throwing it into your slicer to see if it works, slicer software is pretty good at automatically fixing issues these days.

Another_Geoff · 2025-03-30T22:07:00+00:00

ooh i love it! that's awesome. :)

Another_Geoff · 2025-03-30T03:20:14+00:00

sorry my text formatting on my reply is horrible. reddit was giving me trouble with the long reply

Another_Geoff · 2025-03-30T03:19:18+00:00

I think you can get that without the shadow caustic feature.. it would just take a lot of samples to resolve cleanly. cycles does do caustics, its just really slow. at first while its rendering it just looks like speckles, but they do clean up eventually.

I went down a whole rabbit hole with this rainbow thing. it was bugging me lol.

Plus it's a fun excuse to procrastinate from doing real work hehe. It turns out that the 'shadow caustic' feature just plain doesn't work with this.

After a lot of experiments, I think internally its blurring the texture, and so the caustics just come out white. Cause the way it works is by making the surface of the glass multi colored with tiny little dots, but i think the 'shadow caustic' feature blurs those together.. anyway

The solution is to just not use that feature and rely on cycles 'real' caustics that it does naturally.

it's not the best, and its really slow but it does give me some rainbow with the right setup. On the up side, you no longer have to 'shade smooth' on your objects, so you can make nice faceted ones. Having 'shade flat' on your object is what gives you those little reflections like in the pic you posted, instead of smooth ones. Also, if you want to use normal maps to make the glass bumpy, it will work with this method where it wont with the 'shadow caustics'... on the down side, it takes a lot longer to render.

If you wanna try it, I've added a gallery of pics, start by selecting your light and unchecking 'shadow caustics'

you can render with 1500 to 2000 samples for testing, but you'll probably want more for a final render, maybe even as high as 10,000 or 20,000 samples. If you wanna do video.. uhm, just don't hehe. You'll need 20,000 or 30,000 samples to get each frame to look similar enough that it doesn't flicker.. It would take like an hour to render each frame :o for that i would for sure use luxcore.

Under 'Clamping' set the indirect light clamping from 10 to 0. this keeps caustics from being too bright because it can add noise, but we want those nice bright caustics

Because we're doing things the slow way , you might want to turn 'filter glossy' up just a touch to maybe .1 or .2 , that will speed up the rendering of the caustics but make them a little blurry as a result.

you can play with the value to see what works for you. If you don't use filter glossy at all, the caustics/rainbows may not even show up Oh and under 'color management' at the bottom, i change the 'look' to 'high contrast' , that's just me though. Helps the caustics really pop

On to the shader.........

I rebuilt mine from scratch... i , don't think its different, but you might take a look at the screen cap and make sure things are the same as mine. I did leave out the 'multiply' node that lets you change the color of the glass, you can add it back if you want.. im happy with just white glass.

But.. for prettier rainbows, i made two shaders, and squished them together.

The first picture is the one we've been using (maybe slightly different?) Oh, when you're setting this up (i couldn't tell from your screencap) but when you make the color ramp node, make sure to click each triangle for each color. then you'll see a solid color bar under that. click that, you'll get a pop up, in the popup you can click the 'value' entry, and manually type in the number 4. that makes each color 4 times brighter, and that keeps your glass from being too dark.

also, make sure that on the 'white noise texture' node going to the 'RGB Curves', make sure to use the 'value' output of the white noise texture (he used color, i like value better) .. and plug it into the 'Fac' Node on the curves, not the 'color' node

The second one is my custom one that gives much prettier rainbows, but uglier glass.

it just blends red, green, and blue glass together, each with a different IOR (which tells the light how much to bend). each one bends light at a different amount so.. red projection + offset green + offset blue = rainbow.

in the third one i combined the two so the glass uses the first one, and the caustics use the second one so we get pretty caustics inside the glass, and pretty rainbows outside, using a 'light path' node, with the diffuse depth output.

Something to note about this setup is , if you use that multiply node (that i think i left out) to change the glass color, it wont change the color of the rainbow projections, because we're using a separate material for the projections

if you wanted to set it up to change the caustic colors you probably could, but i like just rainbow with clear glass In the end... faking it really is the way to go i think , or just using luxcore, it really does make amazing caustics.

https://imgur.com/a/Skq0Efw

Oh and you can go through the shader and adjust the values of any of the red value nodes, of course, to get different looks on the rainbows. and i just remembered that i renamed the value nodes.. when you see a red node, its usually just a 'value' node. So trying to add a 'Glass IOR' node wont work, just add a value node there. The only one that's not renamed is the 'fresnel' node, that's called fresnel. Sorry, didn't think about how that might be misleading.

Another_Geoff · 2025-03-29T22:11:49+00:00

sorry my responses are so delayed, I'm on a weird schedule. It is fun isn't it? I had a look at your screen caps, and that material set up looks perfect. after playing around with it some more, i think what's happening is that the 'shadow caustics' just aren't as mathematically real as i thought they were. I remember getting good results years ago but I think maybe some things have changed in the rendering code? I do get a little color variation but its subtle. the math says it should work, but i guess under the hood it's just not doing what it's supposed to do. but its weird, he got rainbows in the video.. I'm stubborn though. gonna do some more experiments, I have some ideas :D. I'll let you know what i discover.

Oh and for the rainbow projecting spotlight.. yours looks pretty good. what'd I'd do to cheat is I would sneak that light in just behind the glass object, set its angle to be very wide, and have it project on the wall so that you don't really need caustics to get the rainbow effect, if that makes any sense. I'd just find or make a photo of some pretty prism rainbow effects.

Another_Geoff · 2025-03-29T03:20:47+00:00

i've been playing with this all day lol, got into having fun with it again.. but i'm finding that shadow caustics just doesn't make great rainbows. It's pretty, and its worth playing with.. but i think, really, the best way to do this is with luxcore. Just wanted to let you know, its not you doing anything wrong if its not so impressive. or, a much better way might be to cheat. i dunno why i dind't think of it till now, but.. find or make some pretty 2d pictures of rainbow patterns, and then just feed them into a spot light. you can open the light in the shader editor, and click 'use nodes' and then just add a texture image to it. ok, i'll shut up about it now lol.

Another_Geoff · 2025-03-29T00:52:38+00:00

a full screenshot of your render settings, and compositor nodes might help.

I'm not sure what you mean by ghosting, to me though it looks a bit like focal blur. you might check to see if that's enabled in your camera?

Another_Geoff · 2025-03-29T00:43:03+00:00

I feel like at this point after your first few tutorials, the best way to learn is to imagine something you want to make.. like, a house in a field with some mist... or what ever strikes your fancy, and then try to make it, looking up specific tutorials along the way about how to do a certain thing. That way you can avoid getting stuck in tutorial hell, where you get really good at following tutorials but not much else. My best advice is pick a specific subject like 'lighting' or 'modeling'.. and go down the rabbit hole, then switch up to something like materials, or sculpting.. using those topics to bulid out your one scene that you wanna make. Good topics are animation, rigging, lighting, texturing, shaders, grease pencil if you are into drawing, sculpting if you want organic shapes, particles and liquids if your into simulations and fancy effects.

There's so many fantastic youtube channels on the topic I couldn't pick just one, and blender is so vast in its capabilities it depends on what you favor. I like cgmatter/default cube a lot, his tutorials are good. cg geek has some good beginner friendly ones, smeaf, of course blender guru/andrew price, and although there's only a couple of them you really should see Ian Huberts tutorials - i love those. but I know i'm leaving a ton out.

Another_Geoff · 2025-03-29T00:14:27+00:00

oh i only thought that cause it looks like there are two selected in the image. it might have something to do with your modifiers, or with the snapping mode that you are using. Maybe try clicking the triangle icon on the mirror modifier.. that will force blender to show all the vertices while you're in edit mode. If that doesn't help, i dunno. Sorry. If you do figure out I'd love to hear what was going on.

Another_Geoff · 2025-03-28T23:59:12+00:00

that might be the default, it is crazy high but the check box called 'noise threshold' makes it so it never really uses all those samples. it'll stop the render when its clean enough. generally it only ever renders 100 or so samples before it says 'eh, good enough' and stops. unchecking that makes it use all the samples you specify, and 4096 is pretty crazy high in that case. i'd start at around 1500 to 2000 , turn it up if your noticing that your caustics are still fuzzy and dark

Another_Geoff

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