fire

fire — Animated Particle Flames

Fire in games is almost never a video clip and never an AI-generated sprite. It's a pile of additive billboard quads emitted from a cone, each running a noise-distorted UV through a hot color ramp (red → orange → yellow → smoky alpha-out). Think Skyrim torches, Doom Eternal's pyre, BotW's bonfires — all built from this same recipe with different dials. This skill writes the shader, the controller, and the node tree, then wires them into the open scene. Authoring, not generating.

When to use

• "Add fire to this torch."
• "Make a campfire / bonfire / hearth flame."
• "Light the brazier."
• "I need a candle flame on this candlestick."
• "The dragon needs a flame breath" (use this for the persistent emitter; pair with a one-shot muzzle-flash for the burst).
• The player set something on fire and you need a continuous, physically-anchored flame.

When NOT to use

• The user wants an object to burn away (mesh disintegrating with a fire edge) — route to dissolve. Fire is a separate effect; pair them.
• The user wants smoke without flame — go straight to smoke. (Most fires want a smoke trail above; spawn this recipe and add smoke on top.)
• The user wants a one-frame muzzle flash from a gun — that's muzzle-flash, not fire.
• The user wants 2D fire on a UI element — use canvas_item shader; this recipe is spatial/particles.
• The user wants stylized magic flame (blue, purple, ethereal) — use this recipe and load the magic-fire variant in the cookbook below.

Recipe

1. Files to create

addons/vfx/fire/fire.gdshader              # spatial shader for the visual quad
addons/vfx/fire/fire_process.gdshader      # particle shader for the simulation
addons/vfx/fire/fire_controller.gd          # parameter dials + lifetime
addons/vfx/fire/fire.tscn                   # reusable scene (instantiate per torch)

2. Visual shader code

addons/vfx/fire/fire.gdshader:

shader_type spatial;
render_mode unshaded, blend_add, depth_draw_never, cull_disabled, shadows_disabled;

#include "res://addons/vfx/_building-blocks/noise-3d-fbm.gdshaderinc"

uniform vec4 color_hot   : source_color = vec4(1.0, 0.95, 0.55, 1.0);
uniform vec4 color_mid   : source_color = vec4(1.0, 0.45, 0.10, 1.0);
uniform vec4 color_cool  : source_color = vec4(0.85, 0.10, 0.02, 1.0);
uniform vec4 color_smoke : source_color = vec4(0.05, 0.04, 0.04, 0.0);

uniform float noise_scale     : hint_range(0.5, 8.0)  = 3.0;
uniform float noise_speed     : hint_range(0.0, 4.0)  = 1.4;
uniform float distortion      : hint_range(0.0, 0.6)  = 0.20;
uniform float emission_energy : hint_range(0.0, 8.0)  = 3.5;
uniform float soft_edge       : hint_range(0.01, 0.5) = 0.20;

void vertex() {
    // Billboard the quad toward the camera (view-space).
    MODELVIEW_MATRIX = VIEW_MATRIX * mat4(
        INV_VIEW_MATRIX[0],
        INV_VIEW_MATRIX[1],
        INV_VIEW_MATRIX[2],
        MODEL_MATRIX[3]
    );
}

void fragment() {
    // CUSTOM.x is particle age 0..1 (set by the process material).
    float age = CUSTOM.x;

    // Distort UVs with scrolling 3D noise so the flame writhes.
    vec3 np = vec3(UV * noise_scale, TIME * noise_speed);
    float n = fbm3(np);
    vec2 uv = UV + vec2(n - 0.5) * distortion;

    // Soft round mask, hottest at the bottom-center, cooler toward the top.
    vec2 c = uv - vec2(0.5, 0.15);
    float r = length(c * vec2(1.0, 0.55));
    float mask = smoothstep(0.55, 0.55 - soft_edge, r);

    // Color ramp by particle age (0 = hot bright, 1 = smoky alpha-out).
    vec4 col;
    if (age < 0.33) {
        col = mix(color_hot, color_mid, age / 0.33);
    } else if (age < 0.75) {
        col = mix(color_mid, color_cool, (age - 0.33) / 0.42);
    } else {
        col = mix(color_cool, color_smoke, (age - 0.75) / 0.25);
    }

    // Add the noise as a brightness modulation so flames flicker.
    float flicker = mix(0.6, 1.2, n);

    ALBEDO = col.rgb * flicker;
    EMISSION = col.rgb * flicker * emission_energy * (1.0 - age);
    ALPHA = col.a * mask * (1.0 - age * age);
}