Intro to Simulation Nodes - Geometry Nodes Tutorial

Advanced Geometry Nodes course: www.canopy.games/p/advanced-g...
Grab the beginner course: www.canopy.games/p/bcs-geomet...
Take part in the TrueVFX Winter Wonderland competition: true-vfx.xyz/
In this tutorial we have a play with the experimental simulation nodes builds. Learn to build a responsive, growing, branching system in Geometry Nodes.
Blender Experimental builds: builder.blender.org/download/...
(mine will be an archived build from 10th Dec 2022)
Final lesson file: / 76351567
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Geometry Nodes Toolkit: gum.co/erintools
Merch? erindale.threadless.com/
Discord: / discord
My Courses:
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www.canopy.games/p/advanced-g...
www.canopy.games/p/bcs-geomet...
www.canopy.games/p/procedural...
Contents:
00:00 - Intro
01:30 - TrueVFX competition
02:00 - Input Mesh
05:05 - Looped Extrusion
11:25 - Noise
14:40 - Branching
22:50 - Direction lerp
28:36 - Following a surface
35:40 - Skinning the splines
38:00 - Controlling radius
47:25 - Adding caps
52:24 - Animation control
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[@mickyr171]

If you use a double cross product you can get a better result as the mushrooms grow upwards still but follow the surface instead of growing side-wards when they sense the surface, so, instead of just a cross product which will give you a vector pointing 90 degrees along the surface and give you that spiraling issue, you take a cross product of that cross product mixed with the surface normal again to point upwards but follow the surface if that makes sense lol, essentially creates a tangent to the surface while still moving in the same direction instead of turning to flow horizontally across the surface

[@mickyr171]

If you find it doesnt work for you, try flipping one of the cross products inputs and it should work fine, forgot to add that bit

[@AnittaDeady]

omg i just googled it, so (double cross product)is a thing, i learned somthing today❤

[@martinhaugen8515]

Amazing, worked like a charm! Thanks for the tip!

[@Erindale]

Merry Christmas and a happy New Year!

[@naughtynome4491]

Merry Christmas, thank you for your amazing geo node magics

[@leoz96]

Merry Christmas!

[@nicholascureton933]

Merry Christmas!

[@elschilling]

This is so cool, inspiring and fun! Best Christmas gift of the year! Now I feel encouraged to try simulate the growth of my passion fruit climbing plant :))) I'm very grateful, thanks a lot for sharing!

[@fakecubed]

Some tips for anyone else who wants to play with this branch: 1) Don't be shy about using attributes. Use lots of attributes. Use attributes for everything. Attributes are your friend. My experience with custom attributes before trying out this simulation branch was limited. I forced myself to learn a lot more about them because for simulations they become so incredibly powerful. 2) In particular, I find that boolean attributes that let me branch off geometry based on these booleans is a really powerful workflow. You can take your simulation input geometry, split it off into branches that use a delete geometry on anything not that boolean attribute. Then, right before the simulation output, rejoin your branches. It basically lets you do parallel simulations in one tree, but fully interactive between the branches as you need to pass around values and geometry and such. 3) Store the current frame number on any newly created geometry in the simulation. You can set the ID to this, if you aren't using the ID for anything else, or use a custom attribute. This way you can delete geometry that gets over a certain age with a simple compare and some basic math, or you can use the age of a point to drive a shader. Or anything else like that. Knowing how old things are in the simulation is a really useful data point with infinite uses. 4) Geometry switches don't allow fields in for the boolean input, but you can use the attribute statistic node and compare nodes in various combinations to make switching possible. In particular, you can join in the results of a switch where the true value is some new geometry you want added, and then leave the false empty. You can do stuff like find the nearest point to a particular other location, and then only create new points at the location of that point, when a certain event happens during the simulation. 5) Save often. The branch is really unstable right now, and it's also easy to accidentally create way too much geometry way too quickly, start running the simulation, and crash.

[@briansnider7391]

Wow! Another of your videos just popped up in my feed. This too, is very relevant to something I need to implement in my upcoming project!

[@totochandelier]

very serious approach, appreciate, thx a lot !

[@ramennoodles7328]

Absolutely fantastic tutorial

[@__leoayres__]

Thanks for this great Xmas gift! 💝

[@Hadrhune0]

This is exactly what I was looking for a month. Thank you for sharing, Erindale, and have some good times in Christmas time.

[@Erindale]

Thank you! Hope it helps

[@kenjinks5465]

Merry Christmas, love to see you talking about vector math. I should try some of this stuff out, it is getting interesting.

[@Erindale]

I think you'd get on well with it

[@mdriaz2002]

Ur stuff is so amazing! Everytime I think I know something, you're somehow able to blow my mind!!! Also the vertex neighbor thing is so smart, I dealt with it by initializing the boolean before the loop but ur method is much smarter! Tysm for the great vid and I hope you have a great Christmas and a happy new year!

[@Erindale]

Thank Riaz! Hope you have a great break

[@danialsoozani]

merry christmass and once again my mind couldn't handle all the tricks cuz i'm new to this but I really enjoyed the 1h journey. the problem solving ability you have is amazing!!

[@Erindale]

Thank you! Merry Christmas

[@FarukAhmet]

Awesome Christmas gift, thank you!

[@Erindale]

Merry Christmas

[@rosedaveproductions1528]

I learned so much from this video, as well as some of the youtube comments. Thank you Erindale for a great educational resource!

[@b105cz]

What an insanely helpful tutorial. Thanks a lot! I need to dust off my knowledge of vectors it seems :)

[@todesdigga3891]

Baaaam! Wow this is so great! To be honest I hit my limits pretty quickly when it comes to deeply understanding what you did there (always been bad at math), but I am eager to copy this and play around with values to get a grasp on the possibilities. I am so happy that geonodes keep evolving and that there is such a great community pushing its limits. Thank you for this tutorial, the shrooms look great.

[@Erindale]

Yes! Enjoy - it's real fun what you can get when you start playing

[@nyuh]

YIPPEEEE A SIMULATION NODE TUT THANK YOU AND MERRY CHRISTMAS

[@Erindale]

Yaaaas merry Christmas!

[@nastyartist5806]

I need more tutorials like this

[@brurpo]

Hey there! Always awesome videos! On the split, you dont need to store that block attribute. You can use a modulo. Basically you add one to the value you want to split and use it as modulo. Change the comparison to equal. So for 10 you have trailing>modulo11>equal10. After that to prevent more than one split, you use vertex neighbours and compare to less than 2, and just use an and operation after the equal. You can also multiply the equal comparison to a random value, before the and comparison. This way you add the randomness, but the split value becomes a minimum length to split.

[@UTubeSuhail]

This is so mind blowing Erin!! I would have never thought of using cross product to walk along a surface. Hopefully someday I will be able to think like you haha.

[@Erindale]

Thanks Suhail! Your learning curve is ridiculous so you’ll surpass me easily

[@Tony-cm8lg]

Yeah the cross product of two vectors gives the normal of the plane containing those two vectors. It’s magnitude is also the area of the parallelogram having the two vectors as sides. On the other hand the scalar triple product of three vectors gives the area of the parallelepiped with those three vectors as sides. Maybe that’s useful too

[@timdub_cg]

Wow, that looks like a more efficient way to grow something instead of trimming curves. Thank you, this is very helpful for me.

[@Erindale]

Glad it's useful!

[@crisishotl1ne]

I did this exact thing with the funny buffer workaround so this is a great reference for switching over to sim nodes !!

[@crisishotl1ne]

RE branching What I did is pretty much what you did, but I extruded certain vertexes instead of duplicating them. This difference mostly doesn't matter but for the method I was using to reduce the amount of points it ensured that I could keep it connected to the rest of the mesh. Of course that means the mesh island thing doesn't work but I think I used something else for the seed values for noise and stuff so that didn't matter

[@Erindale]

As soon as you convert to curves it makes them separate anyway 🤷‍♀️ glad you did something similar though, I was worried there would be a much simpler method

[@joaomacaumaia3834]

your videos are great!!!!

[@totheknee]

29:06 - "If you aren't that familiar with vector math..." *LEARN* VECTOR MATH! You won't be sorry. I'm not joking.

[@OnePatrix]

I followed some tutorials about Simulation Noded And I was able to understand them besides one thing : Why People used 2x store named attributes in simulation nodes and before simulation nodes with the same name. Now i Understand why - Because of First simulation iteration. Thanks that you explained it to me :D

[@Erindale]

Glad it's making sense! That's the secret to these loops

[@yuvaraj8492]

😍Wow, Now we can create a universe inside blender.

[@gomdemon]

very smart but very impatient, bro, you go very fast

[@nicolanarracci]

Amazing.

[@heyjude9537]

thank you for this

[@Erindale]

Thanks

[@dialectricStudios]

amazing

[@nealgrieb6660]

Merry Christmas Erin. I wonder if the explosion of branches happens because of the way the newly generated island indices are stored. Can you output the island index as a named attribute and plot them? I'd be curious to see the results. What happens if you set the seed with the island index value instead?

[@garthtingey8061]

I think I have a solution to the massive branch explosion at around 21minutes. The block value is only applied to vertices that have already branched of. If a vertex hasn't been branched off of, then it still could be branched off of again. I don't know why this happens, but I have a solution: automatically set block to true for any vertex that isn't at the end of a branch. This can be easily done using the Boolean math nodes. Take the top output from the extrude mesh node. Plug it in to a Boolean math node set to NOT. Then take the output of the NOT node and plug it and combine it with the input to the node that stores the block attribute using another Boolean math node set to OR. I tried this and it was very successful.

[@johnsonbaugh6878]

This was really great. The "spline explosion" is just an exponential growth curve, right? By setting the probability low you stay below the "knee" of the curve within the time of the animation but if you ran it for a few hundred more frames you'd end up with thousands of splines regardless. Also this is a small thing but you could avoid the "point selection" box by initializing your top attribute before the loop input.

[@omri2398]

hey about the explosion at 21:20: i think it happens because the branched vertex recieve their random value from their "parent", so if their value is 1 for example, they will branch out every frame

[@Erindale]

Yeah I think you're right. It's just not very intuitive when you first encounter it 😁

[@rethburg]

Absolutely amazing tutorial! Mind blown! My only question is: Is there any way to counter the flickering tangent? Some sort of interpolation?

[@Erindale]

You'd have to maybe try averaging the tangent over several points 🤔 that might work

[@quackers969]

an hour long Erin tutorial lezgoooooooooooo

[@Erindale]

Truly a gift

[@martinhaugen8515]

This was amazing to follow! Great tutorial! Did my first geometry node based on this, works like a charm! Say I want to add a function that makes the branches follow an empty, like it being attracted to it, is there a way to achieve this?

[@Erindale]

Certainly is! The direction right now is based on the noise biased in the Z direction. You want to read the location of an empty with an object info node. If you do “empty location - position” then you’ll return the direction from the branch to the empty and you can use this instead for the growth direction

[@Tony-cm8lg]

I don’t know how much maths you know but when I was in grad school i read Elementary Differential Geometry by O’Neill and Differential Geometry of Curves and Surfaces to learn some basics of differential geometry. The latter book is easier in my opinion and has beautiful illustrations and I think would be more geared towards applications in modeling, the first one jumps into differential forms which I don’t think is useful in blender. The background has enhanced my Blender experience slightly but I can’t imagine the crazy stuff you could do with all of that. You could probably also look into differential topology which talks about properties of smooth manifolds. I have no idea if this kind of pure maths would be helpful to you, I’m not anywhere near your expertise in Blender and geo nodes so I really don’t know what your thought process is, but just a thought! Merry Christmas, God bless 🙏

[@Erindale]

That sounds super interesting! I got on okay with maths at school but I don't have any formal education in it beyond that. Everything I know about vector math etc I only intuitively understand by observing it in Blender. I couldn't tell you what cross product is actually doing or how to solve it with pen and paper. I "know" about as far as arithmetic and trig 😅 I'll definitely have a look at that book! Merry Christmas

[@Tony-cm8lg]

@@Erindale Oh really! you seem pretty proficient to me! You’d be amazing at it then, I mean you’ve got such good intuition for how the operations work. I would also recommend as a more introductory text looking at a multi variable calculus (which is basically, loosely speaking, calculus in three dimensions) book then, you’d have a lot of fun with it (as far as math can be fun). A lot of students struggle with multi-variable calculus because they can’t visualize what’s going on in three dimensions, but you’re obviously a master at that already!

[@horiamoldovean6074]

Hey there Erindale, considered recreating some of the complex goemetry nodes from Albin Merle? I know he provides files but would be very interesting to hear and see an explaination on how the effects work and the thought process? Cheers!

[@Erindale]

Cool I'll have a look

[@VerminWorm]

15:20 were there any changes in geo nodes to invalidate this setup as I cannot seem to follow along with the trailing effect shown in this tutorial.

[@rewindcat7927]

🤩

[@sander-wit]

Hi Erin, I tried recreating this setup in 3.6 Alpha (Feb 28 build) but my 'top' named attribute is messing things up, it gets checked for all new verticles, not just the latest top verticles. So each frame my total vert count just about doubles. I tried removing the named attribute before setting it again, but that didn't work for me. Do you know a workaround for the new Blender build?

[@grafgrantula6100]

I had the same problem, and actually posted a comment including a screenshot of the workaround, but I think it was deleted since it's an external link. I'll give you the short version, you'll likely be able to figure the rest out yourself: You need to subtract all points that have two neighboring vertices from the "Top"-Selection socket of the Extrude Mesh node, because that way you only get the beginning and end points of the "splines". You need to do all that in between the Extrude Mesh and Store Named Attribute nodes. You can get that done using three additional nodes: 1. "And" Boolean Math node to remove unwanted points from the selection 2. "Less than" Math node to compare the neighbor count to less than two 3. "Vertex Neighbors" node to get the vertex count I hope this is helpful enough.

[@sander-wit]

@@grafgrantula6100 Thanks for taking the time to explain! I will check your technique later today. Cheers!

[@DerWavezz]

@@grafgrantula6100 Good thing i found your comment, i was questioning my sanity for a while. It works, thank you.

[@condopony1242]

@@grafgrantula6100 This solution works for me. The AND node goes between the OR node and the selection. The other input of the AND node is connected to a Less Than (Compare), which in turn is set to 2 and also connected to a Vector Neighbors node.

[@nobutanaka4434]

This tutorial video was truly fantastic. There were many insightful points to learn from, such as the clever techniques involving branching, bifurcation, and control over growth speed. It was highly educational. Currently, I'm attempting to add color to each mushroom in my project, but it's not going well. When I assign an index to each vertex initially using mesh islands, it seems to get mixed up around the final stages. In the rendering view, the colors appear to be blending or mixing in an undesirable way.

[@Erindale]

Is it flickering as if there’s intersecting geometry? If so and you’re assigning an index in geo nodes and using that as a seed for colour in the shader, you could try assigning the colour in geo nodes and then just read that attribute directly in the shader

[@nobutanaka4434]

OMG！you are so amazing!! it worked! thank you! I initially used white noise in the shader, but it didn't seem to work well. Really appreciate it! Keep up the good work!@@Erindale

[@Erindale]

Great! This is a known bug so hopefully they’ll fix it some time. As far as I’m aware, because shaders don’t have integers the seed attribute is being brought in as a float and then floating point precision errors ends up putting a very slightly different value for each pixel and it’s causing that flicker. Glad the work around is working 🙏

[@nobutanaka4434]

Thank you so much for the detailed explanation. I understand it very well. Let's continue to enjoy Blender together in the future!@@Erindale

[@shmuelisrl]

for the radius thing you did, it would probably be easier to just make a loop index and map range or math it. it'll be much easier, fewer nodes, and faster.

[@Erindale]

Hm that is a good idea actually! It would work in this case but not if you have branches terminating before the simulation ends 🤔

[@shmuelisrl]

@@Erindale what do you mean?

[@MsGe5]

❤

[@1NightInParisOfficial]

How do you get the little timers above the nodes? Thanks for the upload

[@Erindale]

Up in the node tree overlays drop down you can turn on node timings

[@kapil4457]

It was a great tutorial...loved it....but when I was trying to export it as a .glb file I could not see colors in the output...can you please show your export setting or the steps required to export it as a .glb file where we get all the materials and textures applied

[@Erindale]

Wouldn't you need to store your materials as vertex colour for a gltf export? Or maybe just using base colour. Either way I'm not sure geometry nodes has all the things in place right now to export properly. I tend to export alembic cache, import that, do what I need to materials and then re export it

[@christopherandrews7615]

All of your explanations about how to get the right value to use to compute the radius at the branch points was well done... but also unnecessary. In your math, the branch index value is canceled out. The value you ultimately calculate is the number of points down from the tip, so whether there is a branch point or not is irrelevant. Other than that, this was fun and I learned some new things.

[@andsgiant]

Let me buy you nasi goreng.., for teaching the essential "branching" and other tricks..!! Merry Christmas to you..!!🧤🧦

[@Erindale]

Thank you!

[@3drwny]

noise subtract Z = 0.2 is amazing branching is amazing cross product is amazing .. all of them

[@Erindale]

Thank you! Can’t wait to see what you’ll make

[@PotatoImaginator]

He looks totally different without his headsets , like he got a haircut lol

[@Erindale]

I always forget online people almost never see me without headphones 😂

[@justnoname._.8350]

previous versions of your toolkit had the "Attribute to instances" function. Where did she disappear to?

[@Erindale]

We no longer need it. Just use a Capture Attribute node before a Realise Instances node and the attribute will be inherited

[@justnoname._.8350]

@@Erindale oh. thanks for such a quick response!

[@fireme2008]

Hi All, Not sure what I am doing wrong here, but when I extruding the points with the "top" "selection" setup with the named attribute, like Erindale's all same values on every node. I'm looking at 10+ million rows at frame 20 which results in a blender crash shortly after But Erindales is at 2,400 by frame 118. The only difference I can see is the "Store named attribute" node now has a selection input now?

[@Erindale]

You should be able to find the solution in the comments here. Someone definitely posted it about a week ago or so to someone else's comment

[@AnittaDeady]

21:20 not (greater than) i think you should use (equal)

[@Nicolaskaw]

Viewport preview works fine and nice but in render (animation) it resets and doesnt do any simulation - when doing stills, the simulation shows up? i have no idea whats going on. :(

[@Erindale]

Sounds like it could be a bug... Does it happen for all render engines? Does a viewport render animation work? I'd probably report a bug if you're having this issue with the latest simulation nodes build

[@Nicolaskaw]

@@Erindale yeah, i am using your exact build from dec10! tried switching the render engines and somehow it works in eevee. normally, i only bother with cycles. when looking closely, you can see the tips from the curves move in tiny bits, but then resetting after 2-10 frames (in cycles.)

[@Nicolaskaw]

@@Erindale okay so, i have no idea how thats correlated but when turning off motion blur, it works:D blender stays a mystery

[@Wa_Animation]

I can't find the Simulation Noded version of blender available for download, can anyone help me out？

[@Erindale]

You should find a branch build here from the 23rd or if you want the same build I used, it's under the Archived Builds link at the bottom builder.blender.org/download/experimental/

[@AnittaDeady]

44:34 Isn't this the same as directly subtracting (Index) from (Point Count)?😹

[@AnittaDeady]

(A+B)-(C+B)=A-C

[@fatralphslippyfist6285]

Does anyone know how to stop the simulation at a certain frame?

[@Erindale]

Use a switch node and a scene time node. Switch from your calculations to just the sim input socket after a certain frame

[@fatralphslippyfist6285]

@@Erindale Thank you, ended up using scene time->less than->switch

[@joaomacaumaia3834]

explodes because is exponencial

[@no-one3795]

Blendini

[@jeffreyspinner9720]

I was wondering if you have considered in your competition event, that ppl with monster computers (e.g., HeelvsBabyface has a non-melting 4090 and only does stuff like stream the updated Witcher 3 game... what a waste of a 4090 that doesn't melt) have an advantage over others that may be more creative and just better, but can't execute the high level things (TT biomes sometimes makes my GPU clutch its chest and die unceremoniously) the guys with monster computers can? Isn't this like Pay to Win? Like Formula 1 racing,* or MMA, is there a way to limit by horse power and/or stratify by weight class... have a global limit of "horsepower" in one competition class, and/or create "weight class" winners like "honorable mentions?"** Merry Christmas and a Happy New Year or later Happy Three Kings day! Or belated Happy Hanukkah. ______________________________________________ * "...a modern F1 engine is no longer called that, it’s called a ‘power unit’ - and that’s because it’s a hybrid. It consists of a petrol internal combustion engine and electric motors powered by an Energy Recovery System." ** Btw, the genesis of this comment happened because you shocked the hell out of me when your clothes changed. It shocked me into thinking, when I was gonna watch this more as "entertainment only" on Christmas day while eating lunch drinking Coquito... one of the few things positive from my marriage.

[@Erindale]

Not my competition but afaik there's nothing to say you can't modify / down res the assets... The main thing that'll get you through is composition, lighting and post processing imo

[@jeffreyspinner9720]

@@Erindale I followed up with the True VFX guys, I was on their server, but to my surprise I left, Idr that... Cool video, I was too afraid to try to start using the "mesh island" node... onwards and upwards (!)

[@unveil7762]

[@unveil7762]

you explain some nice concept here in a really simple way!!! i ll try to do this in vertex shaders in TD ... thanks !!!!!!!

[@Erindale]

Good luck!

[@oodoodoopoopoo]

Aww, you shouldn't have ☺️

[@Erindale]

Enjoy responsibly

[@arktessellator_10]

Again no much explanation just telling😪

[@Erindale]

Feel free to ask questions if you have any :)

[@arktessellator_10]

@@Erindale sorry to put you in this spot, actually I understand everything you do but that comes only after thinking really hard and partially because I come from engineering background (so I am used to such graphics software and its process) with good hold over maths. The thing that bogs me to comment such is the empathy of putting myself into someone who is very mild (pure artist) at such thing and if I with such knowledge could take such long time to understand I wonder how the others with my apposite characterstic but a will to understand do! Anyways not focusing more on problem but what solution we could offer here? Like how we could improve this teaching of procedural flow (which I believe is truly magical) tuned to it's actual and much better right way of teaching.

[@vstreet7583]

Just brilliant! Watch video, try to understand, LOOP x100 times. SWITCH. TRUE. Understand a little, try to create and follow the master. FALSE. Watch video, try to understand, LOOP x 100 times. Repeat. Just brilliant! Absolutely brilliant! Thank you! Dg

[@alejandrocambraherrera8242]

I think you could avoid the staggering when interpolating the branching start by setting the Map Range to some smoothing mode.

[@Erindale]

Would be interesting to try! Let me know how it goes