Mob Flame effect

The mob flame effect is used by the Blaze when it's charging up to hurl fireballs. This is a flip book flame effect that rises over time.

Unlike the earlier particles, this is a regular emitter. It is tied to an entity, thus uses the entity_aabb shape, as we want the flames to appear all over the blaze. As the effect is tied to the charged state, the activation expression is used, tied to the EntityFlag::CHARGED entity variable. This causes the flames to appear when the Blaze is charging, then to disappear when it isn't.

In this case, we use the texture width/height to make the texel "resolution" be one frame of animation, thus allowing advancement of the frames to be just 1:

{
  "format_version": "1.10.0",
  "particle_effect": {
    "description": {
      "identifier": "minecraft:mobflame_emitter",
      "basic_render_parameters": {
        "material": "particles_alpha",
        "texture": "textures/flame_atlas"
      }
    },
    "components": {
      "minecraft:emitter_local_space": {
        "position": true,
        "rotation": true
      },
      "minecraft:emitter_rate_steady": {
        "spawn_rate": "Math.random(15, 25)",
        "max_particles": 50
      },
      "minecraft:emitter_lifetime_expression": {
        "activation_expression": 1,
        "expiration_expression": 0
      },
      "minecraft:emitter_shape_entity_aabb": {
        "direction": [ 0, 1, 0 ]
      },
      "minecraft:particle_initial_speed": "Math.random(0, 1)",
      "minecraft:particle_lifetime_expression": {
        "max_lifetime": 1.25
      },
      "minecraft:particle_motion_dynamic": {
        "linear_acceleration": [ 0, 1.0, 0 ],
        "linear_drag_coefficient": 0.0
      },
      "minecraft:particle_appearance_billboard": {
        "size": [ 0.5, 0.5 ],
        "facing_camera_mode": "lookat_xyz",
        "uv": {
          "texture_width": 1,
          "texture_height": 32,
          "flipbook": {
            "base_UV": [ 0, 0 ],
            "size_UV": [ 1, 1 ],
            "step_UV": [ 0, 1 ],
            "frames_per_second": 32,
            "max_frame": 32,
            "stretch_to_lifetime": true,
            "loop": false
          }
        }
      }
    }
  }
}