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Show HN: Visual diff for 3D printable models

127 points by iamwil 14y ago

iamwil 14y ago
These are STL files, which are used commonly in 3D printing. The models were generated by OpenSCAD (programming language for 3d modeling). As I've worked more on 3D models for 3D printing, I've been wishing for visual diffs in order to make it easier to collaborate with others. Right now, it's a pre-populated demo of a robokitty (because the internet needs more cats). But soon, you'll be able to push to your own repos using git. Let me know if you have some feedback. Thanks!
- acidx 14y ago
  Pretty useful. Although it would be better if you could just send the diff over the wire when trying to look a previous version -- it takes way too much time to download the whole model. Being able to continue inspecting the model in the same position it was before loading another version would be nice as well.
  - iamwil 14y ago
    Ahh, yes, that makes a lot of sense. And then if someone jumps around, send the whole model, but if it's sequential, just the diff will work.
    - delinka 14y ago
      Is this not what git does?
      - iamwil 14y ago
        My understanding of his question was how I rendered the diff of the models. While git does calculate textual diffs, it does not calculate visual diffs of 3D models, which is what I've managed to do here.
        delinka 14y ago
        I'm not talking directly about your method versus the git method. What I was alluding to: if you're planning to use git to distribute your models eventually, perhaps you should have an eye toward optimizing the models and their diffs for use with git. Then, git transmits only the diffs as needed, when needed.
uncoder0 14y ago
This is perfect. We've been using GitHub + OpenSCAD and have been looking for a less hacky way of doing 3D diffs. Signed up!
- iamwil 14y ago
  Awesome! I'll have the accounts up soon, so you can get started on pushing to your own repo.
- bdickason 14y ago
  Awesome. What are you guys using GitHub+OpenSCAD for?
bri3d 14y ago
Neat! Looking forward to seeing OpenSCAD and STL diffs together on the same page - that'd be a powerful OpenSCAD learning tool as well as a good change-management / collaboration tool. Definitely cool to see where this goes - I've been wanting "GitHub + Thingiverse" for a while.
- iamwil 14y ago
  Do you mean OpenSCAD and STL diffs side by side, and live edited, so when you change the code, you see the model change?
  - bri3d 14y ago
    That'd be most powerful as a learning tool (and a sweet "oh wow!" demo). However, just a GitHub-style +/- diff view on the OpenSCAD files next to the STL diff view would be awesome (basically like the GitHub commit-range/pull-request "files" view, but with STL support).
    - iamwil 14y ago
      Yes, I agree. I'll have to find space to fit it, but it makes sense to do so.
  - kanzure 14y ago
    > Do you mean OpenSCAD and STL diffs side by side, and live edited, so when you change the code, you see the model change? Well, there's always openjscad. I don't think it was a direct port, though.
    - iamwil 14y ago
      Yup, OpenJsCad has the ability to do live editing, but it tends to render a bit slow when the models are somewhat more complex. It sends work back and forth to a background worker to generate the polygons, but it still has to send it all back to the main thread. Unfortunately, OpenJsCad doesn't seem to have a high rate of adoption among 3D printing modelers...at least not yet.
mbell 14y ago
Interesting demo. I don't know anything about this space but it seems to download a ton of data every time I look at a different diff (like 8-10 MB). Is there any way to reduce this? As an outsider I don't even understand how that much information could be needed to render this thing.
- iamwil 14y ago
  Yes. I think eventually, I'll have it generate a photo first, and not use webGL as a default. I did it mostly as a shortcut, because it would have been more work to figure out how to make the server generate and cache a picture of the 3D model. In addition, someone else mentioned that I can probably just send the diffs, rather than the whole model.
  - swalsh 14y ago
    Since you seem to understand already the changes in the file, perhaps it would be possible to download (and merge) only the changes?
    - andrewcooke 14y ago
      i suspect it renders the model twice, in different colours, and what you end up with is the "diff" (one reason i think this is that there seem to be artifacts due to rounding error where the two meet). this has the advantage of requiring little processing on the server and, on the client, you can use a generic renderer. i imagine calculating actual 3d diffs is quite complex (and so cpu expensive). the diffs that are being suggested to reduce file size are, i think, just textual diffs on the source. they won't have valid syntax as graphical deltas in their own right. someone please correct if wrong, just guessing here...
      - kanzure 14y ago
        These are definitely not "semantic" diffs on the original source code (in this case, OpenSCAD barf language). When people say that visual diff is hard, they are usually referring to the semantic aspects, not so much the problem of coloring missing or added triangles..
voltagex_ 14y ago
Hope your bandwidth is cheap - how compressible are these files? Also there's a few suggestions to just send the diffs after the initial model which is a really good idea.
- iamwil 14y ago
  It's just using regular gzip. I'm sure I could do more work to further compress the files, but for the time being, I just wanted to get something out to show people, rather than optimize prematurely. :)
vj44 14y ago
that's cool.
nrp 14y ago
I did something similar using Thingiview.js as a base: http://n0r.org/thingiview.js/examples/client_side_diff.html http://n0r.org/thingiview.js/examples/client_side_diff.html Source: https://github.com/nrpatel/thingiview.js https://github.com/nrpatel/thingiview.js
- iamwil 14y ago
  Cool. I did happen upon you solution a couple months ago when I was researching the topic. :) I checked out your snow globe and the augmented reality stuff you're doing in open hardware. Pretty neat!
drone 14y ago
This is really cool. Especially with the potential for ordering parts/BOM management. How are BOM vendors to be chosen?
- iamwil 14y ago
  For now, that's a ways off, but I was picturing the BOM vendors be crowdsourced based on what people have been using to build the project.
  - drone 14y ago
    Cool deal - good luck with it, I'll keep an eye as you move forward. Could be useful to us!
tathagata 14y ago
This is very good. Some suggestions - you should make the the camera point to the center of the model. Also fixing the light to the eye (not transforming it with the model) will make the rendering look good from all angles. Zoom and pan would be nice. Also maybe an orthographic projection will make better sense as the 3D printed models are likely to be quite small.
breckinloggins 14y ago
Feature suggestion: be able to drag your mouse left and right to create a "swipe diff" line that reveals or hides the old version on the left vs the new version on the right. Maybe that's in there, but I didn't spot it.
- iamwil 14y ago
  Ahh, like a cross-fade slider? It's not in there, but I've heard this a couple times now. Thanks for the feedback!
kaib 14y ago
Nice work, really impressive! A few comments: - You actually have at least four diff states you need to visualize, it's like a matrix. One axis is boolean operations (add, sub etc) the other axis is difference between revisions. For example it's hard to see form the diff if material was added or removed between revisions. You can naturally just highlight where things changed but it's a trade off you need to consider carefully and probably sketch out the most common use cases. - I thought for a long while that transparency is an easy way to solve problems like showing diffs. My more graphics savvy co-founder managed to convince me that transparency is usually not a good solution. When you have a transparent surface on top of another surface it feels like you can suddenly get more information on the screen. However, this is obviously not true, you still have 24 bits of color information on the screen however you slice it. What is happening is that you have divided your bits between the front surface and anything behind it. Our experience is that users have a very hard to grasping even basic 3D shapes on a 2D monitor, making it harder using transparency is usually not beneficial. - If you want to do transparency right you need to do something about the render order, I noticed you are rendering the transparent surfaces in a fixed order. If you haven't checked it out already take a look at our project Tinkercad at http://tinkercad.com http://tinkercad.com. Even if the UI uses a direct manipulation paradigm the underlying operations tree is isomorphic with OpenSCAD.
jozefdobos 14y ago
You might want to look at http://3drepo.org http://3drepo.org for a robust integrated solution including diffing and tailored 3D version control.

127 points by iamwil 14y ago

These are STL files, which are used commonly in 3D printing. The models were generated by OpenSCAD (programming language for 3d modeling). As I've worked more on 3D models for 3D printing, I've been wishing for visual diffs in order to make it easier to collaborate with others. Right now, it's a pre-populated demo of a robokitty (because the internet needs more cats). But soon, you'll be able to push to your own repos using git. Let me know if you have some feedback. Thanks!

acidx 14y ago
Pretty useful. Although it would be better if you could just send the diff over the wire when trying to look a previous version -- it takes way too much time to download the whole model. Being able to continue inspecting the model in the same position it was before loading another version would be nice as well.
- iamwil 14y ago
  Ahh, yes, that makes a lot of sense. And then if someone jumps around, send the whole model, but if it's sequential, just the diff will work.
  - delinka 14y ago
    Is this not what git does?
    - iamwil 14y ago
      My understanding of his question was how I rendered the diff of the models. While git does calculate textual diffs, it does not calculate visual diffs of 3D models, which is what I've managed to do here.
      - delinka 14y ago
        I'm not talking directly about your method versus the git method. What I was alluding to: if you're planning to use git to distribute your models eventually, perhaps you should have an eye toward optimizing the models and their diffs for use with git. Then, git transmits only the diffs as needed, when needed.

uncoder0 14y ago

This is perfect. We've been using GitHub + OpenSCAD and have been looking for a less hacky way of doing 3D diffs. Signed up!

iamwil 14y ago
Awesome! I'll have the accounts up soon, so you can get started on pushing to your own repo.
bdickason 14y ago
Awesome. What are you guys using GitHub+OpenSCAD for?

bri3d 14y ago

Neat! Looking forward to seeing OpenSCAD and STL diffs together on the same page - that'd be a powerful OpenSCAD learning tool as well as a good change-management / collaboration tool. Definitely cool to see where this goes - I've been wanting "GitHub + Thingiverse" for a while.

iamwil 14y ago
Do you mean OpenSCAD and STL diffs side by side, and live edited, so when you change the code, you see the model change?
- bri3d 14y ago
  That'd be most powerful as a learning tool (and a sweet "oh wow!" demo). However, just a GitHub-style +/- diff view on the OpenSCAD files next to the STL diff view would be awesome (basically like the GitHub commit-range/pull-request "files" view, but with STL support).
  - iamwil 14y ago
    Yes, I agree. I'll have to find space to fit it, but it makes sense to do so.
- kanzure 14y ago
  > Do you mean OpenSCAD and STL diffs side by side, and live edited, so when you change the code, you see the model change? Well, there's always openjscad. I don't think it was a direct port, though.
  - iamwil 14y ago
    Yup, OpenJsCad has the ability to do live editing, but it tends to render a bit slow when the models are somewhat more complex. It sends work back and forth to a background worker to generate the polygons, but it still has to send it all back to the main thread. Unfortunately, OpenJsCad doesn't seem to have a high rate of adoption among 3D printing modelers...at least not yet.

mbell 14y ago

Interesting demo. I don't know anything about this space but it seems to download a ton of data every time I look at a different diff (like 8-10 MB). Is there any way to reduce this? As an outsider I don't even understand how that much information could be needed to render this thing.

iamwil 14y ago
Yes. I think eventually, I'll have it generate a photo first, and not use webGL as a default. I did it mostly as a shortcut, because it would have been more work to figure out how to make the server generate and cache a picture of the 3D model. In addition, someone else mentioned that I can probably just send the diffs, rather than the whole model.
- swalsh 14y ago
  Since you seem to understand already the changes in the file, perhaps it would be possible to download (and merge) only the changes?
  - andrewcooke 14y ago
    i suspect it renders the model twice, in different colours, and what you end up with is the "diff" (one reason i think this is that there seem to be artifacts due to rounding error where the two meet). this has the advantage of requiring little processing on the server and, on the client, you can use a generic renderer. i imagine calculating actual 3d diffs is quite complex (and so cpu expensive). the diffs that are being suggested to reduce file size are, i think, just textual diffs on the source. they won't have valid syntax as graphical deltas in their own right. someone please correct if wrong, just guessing here...
    - kanzure 14y ago
      These are definitely not "semantic" diffs on the original source code (in this case, OpenSCAD barf language). When people say that visual diff is hard, they are usually referring to the semantic aspects, not so much the problem of coloring missing or added triangles..

voltagex_ 14y ago

Hope your bandwidth is cheap - how compressible are these files? Also there's a few suggestions to just send the diffs after the initial model which is a really good idea.

iamwil 14y ago
It's just using regular gzip. I'm sure I could do more work to further compress the files, but for the time being, I just wanted to get something out to show people, rather than optimize prematurely. :)

vj44 14y ago

that's cool.

nrp 14y ago

I did something similar using Thingiview.js as a base: http://n0r.org/thingiview.js/examples/client_side_diff.html http://n0r.org/thingiview.js/examples/client_side_diff.html Source: https://github.com/nrpatel/thingiview.js https://github.com/nrpatel/thingiview.js

iamwil 14y ago
Cool. I did happen upon you solution a couple months ago when I was researching the topic. :) I checked out your snow globe and the augmented reality stuff you're doing in open hardware. Pretty neat!

drone 14y ago

This is really cool. Especially with the potential for ordering parts/BOM management. How are BOM vendors to be chosen?

iamwil 14y ago
For now, that's a ways off, but I was picturing the BOM vendors be crowdsourced based on what people have been using to build the project.
- drone 14y ago
  Cool deal - good luck with it, I'll keep an eye as you move forward. Could be useful to us!

tathagata 14y ago

This is very good. Some suggestions - you should make the the camera point to the center of the model. Also fixing the light to the eye (not transforming it with the model) will make the rendering look good from all angles. Zoom and pan would be nice. Also maybe an orthographic projection will make better sense as the 3D printed models are likely to be quite small.

breckinloggins 14y ago

Feature suggestion: be able to drag your mouse left and right to create a "swipe diff" line that reveals or hides the old version on the left vs the new version on the right. Maybe that's in there, but I didn't spot it.

iamwil 14y ago
Ahh, like a cross-fade slider? It's not in there, but I've heard this a couple times now. Thanks for the feedback!

kaib 14y ago

Nice work, really impressive! A few comments: - You actually have at least four diff states you need to visualize, it's like a matrix. One axis is boolean operations (add, sub etc) the other axis is difference between revisions. For example it's hard to see form the diff if material was added or removed between revisions. You can naturally just highlight where things changed but it's a trade off you need to consider carefully and probably sketch out the most common use cases. - I thought for a long while that transparency is an easy way to solve problems like showing diffs. My more graphics savvy co-founder managed to convince me that transparency is usually not a good solution. When you have a transparent surface on top of another surface it feels like you can suddenly get more information on the screen. However, this is obviously not true, you still have 24 bits of color information on the screen however you slice it. What is happening is that you have divided your bits between the front surface and anything behind it. Our experience is that users have a very hard to grasping even basic 3D shapes on a 2D monitor, making it harder using transparency is usually not beneficial. - If you want to do transparency right you need to do something about the render order, I noticed you are rendering the transparent surfaces in a fixed order. If you haven't checked it out already take a look at our project Tinkercad at http://tinkercad.com http://tinkercad.com. Even if the UI uses a direct manipulation paradigm the underlying operations tree is isomorphic with OpenSCAD.

jozefdobos 14y ago

You might want to look at http://3drepo.org http://3drepo.org for a robust integrated solution including diffing and tailored 3D version control.