How I built a realistic grass shader in UE5! Shader driven bend, clump, tilt, wind and more!
ฝัง
- เผยแพร่เมื่อ 25 มิ.ย. 2024
- Files available as a Tier 3 reward on my Patreon: / ghislaingir
Twitter: / ghislaingir
Mastodon: @GhislainGir@mastodon.gamedev.place
Links:
Ghost of Tsushima Tech Talk: • Procedural Grass in 'G...
Tech Art Aid - Shader Optimization: • Shader Optimization - ...
0:00 Intro
1:00 Context
2:28 WPO - Base Setup
4:37 WPO - Cards Rotation
11:00 WPO - Clumps
15:50 WPO - Wind
17:52 WPO - Bend
20:25 WPO - Camera Facing
25:53 WPO - Landscape Mask
27:53 Normals
34:55 Opacity
38:41 Pixel Depth Offset
40:00 Color, Spec & Roughness
40:34 Conclusion & Outro
Hey! I'm back with some more shader shenanigans... I hope the breakdown makes sense, I tried my best! :D
Cheers, thanks for your support :) - เกม
![Your Triplanar is wrong. Here's how to make one that works. [UE5]](http://i.ytimg.com/vi/Cq5H59G-DHI/mqdefault.jpg)
Your channel is such an excellent resource for someone learning tech art. I can't believe something this quality is just posted for free on YT. This is now the definitive UE grass tutorial for me. So much depth, yet delivered in an easy to follow package.
Thanks, much appreciated!
haven't seen yr channel for some reason. now I'm big fan, sir
This looks amazing!!!
Wow you are really talented, here i am trying to understand how all these work and yet you were able to create them all from scratch (with years of experience ofc :D )
I was just browsing TH-cam and this randomly poped out. I have never before subscribed so fast. This is gold.
Ty :D
Great video. You are so tallented. Best of luck
Incredible!!! Liked and subscribed. Thank you so much!
Ty! :)
Thank you very much! Very interesting!
Wow this is brilliant!
the Goat. Thanks Ghislain
Beautiful grass
Thanks for the most amazing grass I've ever seen, Ghislain! It's really great and so interesting. When will you publish the announced final part of the journey? I look forward to it.
Thanks! Not sure about the final part :) Working on it, amongst other things...
Thank you sirrr ✨🙏
Lights out killer.
thanks
Nice one! :D
Ty :D Keep up the good work!
For grass alpha, I like to use a distance field alpha instead of playing with mips.
You can easily thicken the grass blades by adding to the alpha and you can fix a lot of shadow problems in the shadow pass that way too.
You can also easily implement a distance fade that “shrinks” the grass blades into nothingness when they are close from the camera with a simple subtraction on the alpha.
Distance field alpha also look smoother than a typical 1bit alpha (which is why they are used for fonts)
Yep! DF alpha is very commonly used and has tons of use. It's a technique I briefly explained in my stylized grass video :)
That's cool! Does that help at all with overdraw or is it the same performance hit?
@@evanlane1690 Quite the contrary, DF alpha is used to gradually increase the amount of masked pixels, thus increasing the amount of overdraw.
Amazing work yet again🔥 I put in a request for a volumetric fog and cloud showcase/tutorial!
Environmental effects are super important and definitely on my todo list. That list is ten foot long at this point tho... no ETA :)
@@ghislaingirardot understandable😂
I was going to subscribe then realised i was already subscribed
😄
Regarding your issue for the geometry script at 8:20, if you generate the final mesh with PCG from random grass blades instead of doing it in blender, you could generate LODs yourself and run the geometry script per instance instead of per mesh component.
Then you also have to encode pivot point in UVs from geometry script.
Interesting! I haven't yet fully explored PCG so this is good information :D
That is indeed, a very fluffy looking grass.
I have had great success with using a distance blend for the forward vs upward normal debate. I always let at least a little bit of the up normal in, but by the time the grass is at its cull distance the normal should be fully upward in my opinion. This ensures the shading is fully consistent with the underlying terrain when the blades are culled. You can use the per instance fade to offset the blend which will break up the transition and prevent a noticeable radius.
Contact shadows (aka screen space shadows) are also often a good option for grass, as after a certain distance I find they're often nearly indistinguishable from shadow maps. I've been using proper cast shadows for the near LoDs but disabling them and using contact shadows instead for farther LoDs. This also helps make it more feasible to use virtual shadow maps, as the WPO cache invalidation is limited to only the nearest grass.
Very good points! I totally agree with the upward normal making the distance culling a bit easier to deal with. Contact shadows can be a life saver for grass as well, yup :D
I hide the transition by simply sinking the grass blades into the ground at a distance.
It's super cheap (just a Z axis offset) and it allows you to pop grass meshes out of existence at much shorter distances (as long as your grass color matches the landscape).
Using PCG, I also distribute grass with a very high cull distance on top of slopes and edges, where you need the grass silhouette to be visible.
@@cedric7751 Both are great approaches I've also used - although I haven't tried using PCG to automate the process of placing the higher draw distance grass - that's a great idea, thanks.
I'm sorry that I can't afford to get into Patreon as I am a student right now. I was super amazed by your work, and I am currently trying to replicate it using the pivot painter addon. I figured out most of the ways across on how to use the pivot painter addon however I have one key questions that I can't seem to figure out.
How did you create the super weird looking grass models? I thought of creating one by one but I am not much confident whether I can achieve similar results and it is super time consuming
I understand that you have a patreon for a person like me to by pass these difficulties but I seriously can't afford to use money as it is my parents. Would you please just teach me on how you created the models.
Kind Regards
Kota
Wow, pas spécialement concerné par le sujet, je lance la lecture par curiosité, juste pour jeter un oeil, et pouf 44 minutes plus tard je suis positivement ravi de m'être laissé entrainé par la richesse de la présentation : tout simplement passionnant ! Merci maitre !!
Merci pour le message! 🙂
Welcome to our environement !
when is the grass model tutorial, its awesome
Let's say it's a work in progress... :p The scope of that third video changed and requires a lot of work. I'm trying to finish other things first.
Looks so realistic & cool.
This should be default behaviour of Megascan grass.
Ty! But no, not something that can applied to existing assets. Grass mesh has to be modeled with this very specific approach in mind :) Plus, it's probably too costly to be the "default" grass.
@@ghislaingirardot ohhh…
Is there anything that can be done to Megascans/existing assets?
Stationary megascan looks great but when wind effects are applied they look so weird and unnatural.
@@IamSH1VA I don't know, I don't actually use megascan assets. I doubt megascan assets have baked pivots tho, so there's only so much you can do with them.
@@ghislaingirardot thanks for the info…
Yes that looks great but let me give you a new challenge: realistic lawn grass. It's something I've really struggled with.
Where is the 10h loop with asmr wind sound, crickets etc.? 😌
Hehe, I'll have to think about it :D
Hey Ghislain,
The content is excellent! I've been following all the tech talks you mentioned and watched the Visual Tech Art video on grass-thanks a lot for bringing the GOD x Ghost grass to Unreal with such a clear process.
However, I'm a bit stuck on one part of the implementation. Why use cards that all face the same direction? I get that it's not just for encoding data in the normal channel since you override that anyway. And since you're encoding the rotation in the normal channel anyway, you end up with static rotations.
Is the reason for keeping the cards unrotated because you need to access their rotation programmatically in the shader? Having rotated cards would make this more complicated, right?
Why not leting the card rotated, use the normal to get the rotation and compute a random rotation relative to that one?
It would avoid recomputing the normals, no ?
Thanks. The x-aligned cards are to programmatically roll cards along their up axis to best face the camera and increase pixel coverage. I mention that in the video somewhere :D That way I can also easily compute the cards forward vector and modulate the wind effect based on it
@@ghislaingirardot Ok I got it! That point on getting better pixel coverage made a lot of sense when I've been watching this part (I binge watch all your videos on grass).
I will get my head around why recomputing that X vector from normal orientation is a more complex idea, I still not quite understand all the vector manipulations.
I will use PCG to generate clumps and the script you shown for geometry scripts which I'm super familiar with.
Exact reason at 18:55, the shader code bends the mesh around the X axis!
@@Jbbriant-Ardaria oh yeah, that reason first and foremost :D I already forgot most of that video tbh
How's performance? It's for big projects?
How to get random vertex normal in maya
Could this grass shader be applied as a material to an imported site model that is a static mesh actor?
No
I'm trying to get this to work on my custom landscape I made with a heightmap. Is there a good way to achieve this?
What's the issue exactly? This grass shader isn't tied to the landscape in any way, besides the grass/dirt layer trick I explained.
Why your wind texture uv can scroll by it texture node self without any time node? 16:01
It doesn't scroll, it's a render target generated via my wind system. I made a video about it.
@@ghislaingirardot oh! Thanks!
Does this grass properly move when a player character walks through it? I apologize, but I watched the video and I still am not clear if it's physicalized in this manner.
No but it would be fairly easy to implement thanks to the way wind is added. You can inject extra offset at the same time as wind, for things like interaction and let the shader do its thing.
@@ghislaingirardot My 2 cents for your next video! 😀😅🤣
@@Pengman19 My existing advanced grass interaction system/video outputs a velocity map that could simply added to the wind offset as-is. No need for an extra video :)
@@ghislaingirardot I will check it out
i was wondering if you have time for personal mentorship, i want to learn shaders for games, tech art in general. I have no resource or a complete solution for learning tech art, unlike texturing and sculpting where you gradually get good at these skills, i find math in general is difficult to self teach.
No mentorship, sorry.
@@ghislaingirardot can you recommend me some sources where I can learn tech art? Online schools, courses or maybe someone you know who teaches?
@@devjitpaul1191 I don't know any TA that offers mentorship and I'm unfamiliar with game dev schools. It's a way too broad of a domain to recommend one 'course' or one specific way to learn being a TA. I fear you just gotta be curious and start figuring shit out on you're own like we all did :D good luck