Flipping Indices - Geometry Nodes Tutorial

[@Erindale]

One day I'll publish a book of these thumbnails

[@Smartroid]

The booking open yet? I'm tryna pre-order 😂

[@jaybah8039]

and t-shirts!

[@masterxeon1001]

obligatory comment about sample index node being the node for transfer attributes now. Excellent and timeless video. Lovely.

[@amritbhakta8498]

Holy cow man, this is exactly what I needed for a project I am working on right now lol, thanks so much!

[@JT11111]

I watched this in its entirety eventhough ive never encountered an instance where I need to flip my indices, hopefully my brain can recall this video the day I encounter that issue

[@Erindale]

You never know when it might jump out!

[@Alumx]

Mom , erindale has been posting those thumbnails again 💀 edit: I love these kind of theoretical tutorials, tbh I was more blown away by how you transferred attributes from grid to line, like I understand how it works but holy hell i'd never reach that just by myself. Geo nodes are already so deep its pretty crazy

[@workflowinmind]

"I see them"

[@Erindale]

Yesss that transfer, once you know how it works with the index, you can do so much!

[@thezachlambert]

Thank you for being my math teacher! I love learning about weird functions through videos like this where I get to see a practical example right away rather than wonder what the heck I would use it for.💕

[@joshudecartier7652]

Thank you, Thank you. For both the example and the Math behind. I've been using Grasshopper for the past 5yrs where Flip Matrix is just a standard component. TBH I didn't realize that there was a simple Math way of doing this.

[@Erindale]

Yeah it's one of those things I'm sure will be added to geometry nodes natively in the fullness of time but for now, a little bit of maths goes a long way! You can actually do most high level things with math nodes. I saw someone make a full curve deform node to make arbitrary meshes follow curves and that was all just maths.

[@georgegibson707]

Thankyou so much, I had to do exactly this to reorder some point indices, and it worked perfectly.

[@Erindale]

Great! Glad you found the video

[@fabbrobbaf]

I figured out by myself the U indexing but the V was by far out of my mental reach eheh...you're amazing Erin! Thanks for sharing

[@Erindale]

Hope it's useful!

[@mdriaz2002]

This is such a good resource! I remember working my ass off to figure this out and even though I did, this would've been a good video to have!! Love your videos man keep up the good work!!!

[@Erindale]

Yeah same it took like an hour to actually reach a solution for me 😅

[@noahmcmahan2196]

Awesome video erin!

[@Erindale]

Thanks Noah!

[@jaybah8039]

This is a perfect example to demonstrate how great is Blender for learning math. Also a question: how do you determine that you should use nothing else but modulo or divide+flooring in these cases? What's the logic behind this?

[@Erindale]

If we think of the values like a gradient I think it's a bit easier. So if we have a gradient and we want it to be split into repeating gradients then we want fraction (0..1), modulo (0..n), or wrap (n..n). And for stepping for the rows you can use snap to get even blocks and then divide to get the step size to 1. Or like we did here, divide first and then floor (which is faster than snap). You just need to identify if you're making repeating ramps or steps.

[@jaybah8039]

@@Erindale yeah, this approach will help to understand it better. Thank you 😊

[@jimmyjames6913]

Hey Erin, Do you know of a way to compare vectors in Geometry nodes? I use Rhino with Grasshopper at work, and there the List handling is pretty good and relativley easy to understand. I have a Curve,Iused the Curve to Ponts Node, which gives me a number of Points on that curve. It also gives me the tangent vector for each of the points. My idea is to compare a list(field) of Tangent-Vectors, to a shifted List of the same Tangent-vectors- in Grasshopper there is a shift List node, which prettymuch shifts the Indices of that List, and therefore lets me compare each tangentvector with its neighbour. Is there a way to do that in Geometry nodes as well? Or do you know a different way of comparing each vector of a list of vectors to its direct neughbour? Greeting, James

[@Erindale]

Lists is something I'm sorely missing in Geo Nodes and why I'm still using Sverchok a lot. It's slower but it's based on Grasshopper. What you can do is take your tangents into whatever you're using to compare eg vector math node. Then take a Transfer Attribute node, set to points, vector, index. Plug your points into the source, tangents into the attribute, and index into the index. But you want to use math nodes to offset the index and you might need to also modulo with the domain size if it doesn't loop around to 0 properly. You can then plug this transfer into the other socket of your vector math node. It's not a "nice" workflow but fields don't exist without geometry, they're just referencing it. Different to Grasshopper where your lists are actual lists of data.

[@jimmyjames6913]

@@Erindale Thanks Erin, I will Try that out- yes, the fact that Lists are not a thing of its own in GN, seems pretty weird. + there is very little documentation on many Nodes so far... that makes it quite hard/abstrakt to get Into Geometry nodes. Is there a dedicated Discord server for geometry nodes, where I can ask questions like these?

[@__leoayres__]

Could you instance the index number(turned to string) on each point?

[@gergelypifko2123]

Hey, do you think it’s worth learning geo nodes, when u could just learn houdini instead? It seems to me hat Houdini has way more to offer especially when it comes to simulations.

[@Erindale]

If Houdini is an option to you then definitely it's worth learning! It has a lot more options because it's been around for more than 20 years longer

[@gergelypifko2123]

@@Erindale Thanks for the quick answer, and for not being biased towards Blender, keep up the good work!

[@bzikarius]

Okay, I knew similar method when I built 2d and 3d arrays from line. not actual flip but good to know

[@mirko124]

Thank you! Is there also a way to shuffle indices?

[@Erindale]

There technically is! Someone came up with a solution on my Discord that manages to do non-repeating shuffling

[@hugoantunesartwithblender]

Im still really noob at geo nodes since i have too much work, But would be possible to use geometry nodes and drivers to get reduced levels of decimate modifier the closer i am to something? For exemple like the nanite system, but only the part of geometry, the close iam to something, the less steps/percentage of decimate modifier i would see

[@Erindale]

Not currently possible as geo node output attributes can't be accessed via drivers. Potentially possible once there's a decimate node though

[@hugoantunesartwithblender]

@@Erindale That would be so cool ! I will propose decimate modifier node on right click select, maybe it gets picked haha

[@Erindale]

Doing a decimate live in blender would be very slow btw. It's totally different to the mesh streaming that nanite does

[@PCgmesforever]

Welcome to another ASMR video

[@Erindale]

Lmao happy little node trees

[@abluzuma2331]

Interesting trick! An alternative to `floor(index/u)` could be `(index-(index%u))/u`

[@Erindale]

This works too! Floor is an extremely fast operation though so definitely worth using when you can 👌

[@JohnWesleyDavison]

Bless your math brain

[@Erindale]

Thanks! I love little dexterity challenges like this

[@workflowinmind]

❤️

[@sphere1810]

flipped thumnail