Basically just a slash effect particle that spawn after upswing on better combat attack.

Forge need Sinytra Connector and maybe a Forgified Fabric API .

Forge doesn't need Sinytra in version 0.0.3!

This mod is possible with only client!

Better Combat Particle on latest Better Combat!

This mod was originally the way for me to give an idea to Better Combat. Since Better Combat dev are interested, now it is merged with Better Combat!. Now i will focus on 1.20.1 only until Better Combat add its own weapon trail to 1.20.1. The way particle work here and there are different. In here the particle info are read through assets, in better combat it read through config. If you have your own particle info simply just copy paste it to the better combat weapon trail config.

About Particle Optimization:
Seems like some particle optimization mod will make this particle not visible in first person because it is too close to camera and decide to not render the particle plane. the only thing you can do is to disable the culling for now.

ABOUT CONFIG:
Config also available in config/bc_particle. there is an option to disable and enable the particle. also the transparency of the particle on lit or non lit.

ABOUT CUSTOMIZATION:

You can check and learn it on assets("data" in v0.0.1)/bc_particle(mod_id)/bc_particle/.json

if an animation doesn't have the particle, it means you don't have it registed on the particle_settings.json. you can make your own resource to add that. example: assets("data" in v0.0.1)/malfu_combat_animation/bc_particle/particle_settings.json

particle_type: type of slash texture. there is slash45, slash90, slash 180, slash270, and slash360.

"x_addition": left/right (right bigger float)

"y_addition": up/down (down lower float)

"local_yaw": local rot of the texture (bigger clockwise)

"roll_set": roll rotation of the plane.

"pitch_addition": pitch add. usually i combine it with y_addition.

{
  "replace": false,
  "values": {
    "malfu_combat_animation:axe_updown_lr": [
      {
        "particle_type": "slash90",
        "x_addition": 0.0,
        "y_addition": 0.0,
        "roll_set": 210.0
      }
    ],
    "malfu_combat_animation:two_handed_up_lr": [
      {
        "particle_type": "slash90",
        "x_addition": 0.0,
        "y_addition": -0.30,
        "local_yaw": 20,
        "roll_set": 130
      }
    ]
  }
}

you can also add more than one particle, you can check the example on bc_particle assets or malfu combat animation for more info.

there is also enchantment_settings.json and weapon_settings. this contain a color settings and light set for enchantment and custom weapon. simply put the enchantment id and its color and light. well just check on the example in bc_particle data. same with particle_settings.json you should be able to make the datapack.

for color_hex and color_hex_sec. you can put string "remove" to set alpha to 0, basically remove the particle. just in case you want to remove particle for some custom weapon or enchantment

Texture is bad? i've reworked it so many times didn't manage to make it really good, can't paint. well just replace it with your own made texture pack.