Slash-Animation with Trails

kajinor · March 19, 2024, 12:19pm

Godot Version

Godot 4.3.dev5

Question

I have been wondering if Godot supports 3D Trails for things like Sword slashes, etc. like you can do in Unreal Engine for example without creating a custom trail-mesh in Blender. All examples I found work with Trail-Meshes created with Blender and I also worked with custom Trail-Meshes in the past but its so cumbersome.

I read that Godot 4.x now has this particle trails feature which I kinda couldn’t figure out yet as there is not much about it online yet. I also read the documentation page about it.

Before I dig deeper into this and experiment more, I would like to know if its even possible to use it for slash effects or if it serves different purposes. I am kinda pretty sure Godot is capable of doing this.

It would be great if someone could lead me to the right direction here. Thanks!

zdrmlpzdrmlp · March 20, 2024, 12:50pm

so far, the GL compatibility mode for Godot doesn’t support particles trail and even sub-emitter
the usual way to use the trail is to add it as a sub-emitter of a main particle
you might just want to find a good shader to make the slash
i just found it by just googling for that

kajinor · March 20, 2024, 2:41pm

Hey, thanks for your reply. I did a lot of research and unfortunately, it seems the particle trails cannot handle this. There have been several issues opened for this in github, a good one is this:

github.com/godotengine/godot-proposals

Add a Trail3D node to draw smooth lines for VFX

opened 03:25PM - 14 Jun 23 UTC

QbieShay

topic:rendering topic:3d

### Describe the project you are working on VFX ### Describe the problem o…r limitation you are having in your project Godot has no 3D trail node Trails are incredibly complicated to get right and require an in-depth understanding of linear algebra and geometry in order to get right. Coupled with that, they also require understanding of how to draw meshes and how to assign UVs. In addition to all of this, rendering also tends to badly deform UVs if there is no subdivisions, which complicates the code significantly for mesh building, and bridging the gap from the emission transform with the last spawned point of the trail ALSO adds complexity. **This is a hard problem that requires very complicated solutions in order to look good and existing plugins tend to not be kept up to date, or have issues** ### Describe the feature / enhancement and how it helps to overcome the problem or limitation Add a trail node (That possibly builds on top of a Line3D node proposed in https://github.com/godotengine/godot-proposals/issues/6151, but the two works shouldn't be dependant on each other) ### Describe how your proposal will work, with code, pseudo-code, mock-ups, and/or diagrams Glossary: Emitter: the (moving) point the trail is emitted from Width: the overall width of the trail Midpoints: points at which the trail is sampled, used as a base to generate geometry Segments: Geometry that is generated between midpoints ![image](https://github.com/godotengine/godot-proposals/assets/7917475/d8ae5560-2985-4058-810d-7dd28bcd2d9b) Curve glossary: ![image](https://github.com/godotengine/godot-proposals/assets/7917475/23f214a4-5d09-4859-a24a-e8509800b504) Line3D node properties: - emitting: wheter or not the trail is emitting - lifetime: how long does the trail live (when turning emitting off, it should take `lifetime` to not see the trail anymore - profile curve: a multiplier for the trail width along its length. - color gradient: a gradient that describes how the color of each midpoint changes over its lifetime. - transform align (Y_NORMAL, BILLBOARD): how trail segments are oriented. Y up will cause the trail to treat the emission Y axis as normal and X axis as binormal and Z as tangent. billboard will orient the trail to always face the camera. - minimum point distance: minimum distance between points before sampling the next midpoint. prevents artifacts. - maximum point distance: maximum distance between points before sampling the next midpoint. - UV mode (TRAVEL_DISTANCE, UNIT_RANGE): how UVs are assigned to the generated mesh. travel distance will create UVs that are in world space, while unit range will ensure that the UVs are always in range 0-1 along the visible part of the trail. **note that there shouldn't be a jump when a segment is deleted because it exceeded its lifetime** Stretch goals: - Bezier interpolation on/off - Pause: pause the trail lifetimes from running out. useful if debugging stuff in engine. NOTE: UV.x should be the length of the trail, while UV.y should be the width, in compliance with how blender organizes UVs on curve meshes by default. ### If this enhancement will not be used often, can it be worked around with a few lines of script? It can be worked around with a lot of lines of script that probably will be buggy and not work under all conditions, or that will not look as good as a skilled tech artist can make them look. ### Is there a reason why this should be core and not an add-on in the asset library? Because trails add an incredible value to any moving object and not having a well designed Godot plugin means that only projects with skilled tech artists will have the expertise to create good looking ones. This is a very hard problem to solve.

There are also several addons trying to implement a 3D Trail Renderer for Godot. For example: TrailRenderer - Godot Asset Library

If this is doable with the same flexibility and features like in Unreal/Unity using Sub-Emitters with Particle Trails, I take everything back. Anyway, I will take a closer look into it again.

Thanks so far.