3d Lighting

3D Lighting for Summer Engine

Outdoor and indoor lighting setups for 3D scenes.

Light Types

Basic Outdoor Setup

1. Directional Light (Sun)

A light is one node plus a few properties: build it with one summer_run_script call. Every scene tool takes a required scenePath, the exact res:// scene to change (get it from summer_get_project_context); the snippets use res://main.tscn. One property change on an existing light is one summer_set_prop.

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summer_run_script(scenePath="res://main.tscn", source="""
func run(ctx):
    var world = ctx.get_or_create("Node3D", "World")
    ctx.add_node("DirectionalLight3D", "Sun", world, {
        "rotation_degrees": Vector3(-45, 30, 0),
        "light_energy": 1.0,
        "shadow_enabled": true,
        "light_color": Color(1, 0.95, 0.9, 1),
    })
    ctx.save_scene()
""")

Warm sunlight: Color(1, 0.95, 0.9, 1). Cool moonlight: Color(0.8, 0.85, 1, 1).

2. WorldEnvironment (Sky + Ambient)

The Environment resource has:

• background_mode — 2 for sky, 1 for color, 3 for canvas (Environment.BG_SKY = 2, BG_COLOR = 1, BG_CANVAS = 3; default is 0, BG_CLEAR_COLOR)
• sky — Sky resource (ProceduralSkyMaterial or PhysicalSkyMaterial)
• ambient_light_source — AMBIENT_SOURCE_SKY or AMBIENT_SOURCE_COLOR
• ambient_light_color
• tonemap_mode

A sky is a Sky resource in environment.sky, with a ProceduralSkyMaterial (or PhysicalSkyMaterial) in its sky_material. summer_set_resource_property only sets properties on a resource that already exists, so build the node, the Environment, the Sky and its material in one script:

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summer_run_script(scenePath="res://main.tscn", source="""
func run(ctx):
    var env := Environment.new()
    env.background_mode = Environment.BG_SKY
    env.sky = Sky.new()
    env.sky.sky_material = ProceduralSkyMaterial.new()
    env.ambient_light_source = Environment.AMBIENT_SOURCE_SKY
    env.tonemap_mode = Environment.TONE_MAPPER_FILMIC
    ctx.add_node("WorldEnvironment", "WorldEnvironment", ctx.find("World"), {"environment": env})
    ctx.save_scene()
""")

Later, one value on that Environment is one summer_set_resource_property (resourceProperty="environment", subProperty="background_mode").

Simpler path: start from the 3d-basic template, which already has a sky, and copy its structure.

3. Fill Light (Optional)

A second, weaker directional or omni for shadow fill:

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summer_run_script(scenePath="res://main.tscn", source="""
func run(ctx):
    ctx.add_node("DirectionalLight3D", "FillLight", ctx.find("World"), {
        "rotation_degrees": Vector3(-30, -120, 0),
        "light_energy": 0.3,
        "shadow_enabled": false,
        "light_color": Color(0.7, 0.8, 1, 1),
    })
    ctx.save_scene()
""")

Indoor / Point Lights

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summer_run_script(scenePath="res://main.tscn", source="""
func run(ctx):
    ctx.add_node("OmniLight3D", "Lamp", ctx.find("World"), {
        "position": Vector3(2, 3, 2),
        "light_energy": 0.8,
        "light_color": Color(1, 0.9, 0.7, 1),
        "omni_range": 8.0,
    })
    ctx.save_scene()
""")

Many lamps (a street, a corridor) are a loop in the same script, not one call per lamp.

Property Reference

Color Format

Always use Color(r, g, b, a) with values 0.0–1.0:

• Warm white: Color(1, 0.95, 0.9, 1)
• Cool white: Color(0.9, 0.95, 1, 1)
• Orange (torch): Color(1, 0.6, 0.2, 1)
• Green (alien): Color(0.5, 1, 0.5, 1)

Baked lighting — what you can and cannot do from here

Real-time lighting (everything above) is fully scriptable. Baking mostly is too on this build — the split that matters is which process runs the bake, not whether a script can trigger it.

So when the user asks for baked lighting: add and configure the LightmapGI node, set the meshes' gi_mode, then run the bake yourself from summer_run_script — lgi.bake(lgi, "res://lightmaps/scene_lm.exr") — and check the returned bake-error enum (0 is OK; BAKE_ERROR_NO_LIGHTMAPPER means no renderer in this process, not a missing binding). Verify with a framing:"camera" screenshot, which renders the real environment. Only fall back to "press Bake Lightmaps in the editor" when no renderer is available. If they want GI with zero bake step, steer to SDFGI (Environment.sdfgi_enabled) or VoxelGI.

Note the related trap: Engine.has_singleton("EditorInterface") returns true even in a headless non-editor process, so it is not a valid capability probe. ClassDB.can_instantiate("EditorScript") returns false outside the editor and is the reliable check.

Fallback (no MCP — edit .tscn directly)

If Summer MCP isn't connected, append the lighting block to your scene file:

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[node name="Sun" type="DirectionalLight3D" parent="World"]
transform = Transform3D(0.866, 0, -0.5, 0.354, 0.707, 0.612, 0.354, -0.707, 0.612, 0, 0, 0)
light_color = Color(1, 0.95, 0.9, 1)
light_energy = 1.0
shadow_enabled = true

[node name="WorldEnvironment" type="WorldEnvironment" parent="World"]

Then create Environment and Sky resources via the inspector or load from .tres.

Collaborative protocol

This skill mutates the scene (adds lights + WorldEnvironment + tunes Environment sub-properties). Always ask before applying: "May I add a DirectionalLight3D Sun with shadows + a WorldEnvironment with a procedural sky?".

From a shell

No Summer MCP tools in this session? Run each one as a command; when summer --version is missing or below 4.0, use npx -y summer-engine@latest in place of summer. Fields are flags in kebab-case (--scene-path res://main.tscn) or one --input '<json>', and summer ops describe <op> prints the exact input. The summer-cli skill has the rest.