Organic Model

Organic Model — Easy-Mode 3D Generation

Organic shapes (trees, rocks, mushrooms, coral, alien flora, crystals, vines, bones) are the most forgiving category for AI 3D generation. Lumps look natural. Asymmetry looks natural. Smoothing-group artifacts read as bark texture. The "melted" look that ruins vehicles and characters is fine on a mossy boulder.

This is the cheapest, fastest way to fill out a scene. Use it liberally — it's the recommended go-to when the user says "this scene feels empty". Each generation is ~$0.30–0.50, and the failure rate is the lowest of any 3D-asset family.

Backing tool: summer_generate_3d. Default hunyuan is great here, but trellis is faster and quality difference is mostly invisible on organic shapes — trellis is the recommended pick when generating many at once.

When to use

• "Make me a pine tree."
• "Generate five different rocks I can scatter."
• "I need glowing mushrooms for the cave."
• "Fill this forest scene with foliage."
• "Alien plants for the planet surface."
• "Coral for the underwater level."
• The user wants visual density without spending a lot of money or time.

When NOT to use

• Character (humanoid, even if "tree-person") → summer:3d-assets/character-model (rigging matters).
• Vehicle, weapon, hard-surface object → summer:3d-assets/prop-model or summer:3d-assets/vehicle-model.
• Tileable ground (grass field, sand) → summer:asset-pipeline/asset-strategy Pipeline 2 (textures, not meshes).
• Animated organic (Venus fly trap that opens, breathing pod) → generate static here, animate in-engine with bones or shape keys.
• A single hero-tree centerpiece (Yggdrasil, the One Tree) — generate via summer:3d-assets/prop-model with higher polycount and detail attention.

Polycount targets

Organic geometry tolerates aggressive polycount cuts because the silhouette is irregular — viewers can't spot poly-count drops the way they spot a low-poly cylinder.

| Use case | Tris | Pass via | |---|---|---| | Hero tree (mid-distance, prominent) | 4k–8k | target_polycount: 6000 | | Background tree (forest filler) | 1k–3k | target_polycount: 2000 | | Distant tree (use billboard imposter) | 200–500 | target_polycount: 400 | | Large rock / boulder | 800–2000 | target_polycount: 1500 | | Small organic (mushroom, fruit, crystal) | 300–1000 | target_polycount: 600 | | Vine / branch decoration | 200–500 | target_polycount: 400 |

Generating a forest? Make 3 hero trees + 5 background trees + 3 rocks at low polycount, then scatter via MultiMeshInstance3D for hundreds of copies at near-zero rendering cost.

Steps

1. Search before generating

summer_search_assets(query="", assetType="3d_model", source="all")

2. Build the prompt

Pattern: + + + isolated suffix. Organic prompts are shorter than prop prompts — the model already knows what a tree looks like.

| Goal | Prompt that works | |---|---| | Pine tree | A tall pine tree with dense green needles and a straight trunk, slight lean. Game asset, stylized low-poly game art, white background, isolated object. | | Oak tree | A wide oak tree with sprawling branches and seasonal autumn leaves in orange and red. Game asset, stylized, white background, isolated object. | | Boulder | A large mossy boulder, irregular weathered surface, patches of green moss on top. Game asset, stylized, white background, isolated object. | | Glowing mushroom | A cluster of three bioluminescent mushrooms on a small mossy base, pale cyan glow, translucent caps. Game asset, stylized, white background, isolated object. | | Alien plant | An alien spiral plant with tendril-like fronds, deep purple with glowing pink tips, growing from a bulbous base. Game asset, stylized, white background, isolated object. | | Coral cluster | A branching coral cluster, bright orange and pink, sea-fan shapes, multiple branches. Game asset, stylized, white background, isolated object. | | Crystal | A jagged amethyst crystal cluster growing from a stone base, deep purple with translucent facets. Game asset, stylized, white background, isolated object. | | Vine | A hanging jungle vine with broad green leaves and small white flowers, ~2 meter length. Game asset, stylized, white background, isolated object. |

Organic prompts that DON'T work:

| Bad prompt | Failure mode | |---|---| | a tree | Returns a generic tree, but inconsistent species across regenerations — the scene looks chaotic. Always specify species. | | a forest | Returns one fused mesh of multiple trees → impossible to scatter. Generate one tree, scatter via MultiMeshInstance3D. | | realistic tree with photoreal bark | Realistic = expensive polycount, ugly when stylized assets surround it. Match scene style. | | a tree on a hill | The hill becomes geometry. Always say isolated object. |

3. Confirm and call

> About to generate pine_tree_01 via trellis, target ~2k tris. ~$0.30, ~30s. OK?

For batch generation, batch the confirmation:

> About to generate 3 trees + 3 rocks + 5 mushrooms (11 generations, ~$3.50, ~5 min). All low-poly via trellis. OK?

summer_generate_3d(
  prompt="A tall pine tree with dense green needles and a straight trunk, slight lean. Game asset, stylized low-poly game art, white background, isolated object.",
  model="trellis",
  options={ target_polycount: 2000 },
  wait=true
)
summer_get_asset(assetId="")
summer_import_asset_by_id(assetId="", path="res://assets/organic/pine_tree_01.glb")

4. Generate variation, not duplication

If the user wants "five rocks", don't generate one rock and copy it five times in the scene — generate five subtly different prompts:

"A medium boulder, mossy granite, rounded shape"
"A medium boulder, weathered limestone, sharp jagged edges"
"A medium boulder, dark basalt, flat-topped"
"A medium boulder, sandstone, layered horizontal striations"
"A medium boulder, mossy granite, tall narrow shape"

Then scatter all five with random rotation. Five unique meshes + rotation = looks like 50 unique rocks.

5. Wire into the scene

| Use case | Wiring | Notes | |---|---|---| | Single hero tree, mid-scene | MeshInstance3D under Node3D | One per scene; nothing fancy | | Forest scatter (50+ trees) | MultiMeshInstance3D with one mesh ref | Single draw call for all instances | | Foliage variety (3 species) | One MultiMeshInstance3D per species | Each species is one draw call | | Distant trees | Billboard imposter (Sprite3D with a tree image) | Switch from mesh to billboard at ~50m via LOD | | Rocks with collision | StaticBody3D parent + CollisionShape3D (ConcaveShape from mesh) | Only for rocks the player can walk into | | Rocks without collision (background) | Just MeshInstance3D | Most distant rocks don't need it |

Hero tree:

summer_add_node(parent="./World/Forest", type="MeshInstance3D", name="HeroOak")
summer_set_prop(path="./World/Forest/HeroOak", property="mesh", value="res://assets/organic/oak_tree.glb")
summer_save_scene

Forest scatter (MultiMesh): create a MultiMeshInstance3D, assign a MultiMesh resource referencing the tree mesh, set instance_count to e.g. 100, and populate set_instance_transform() from a script with random positions + rotations. See summer:scene-composition for the scatter pattern.

6. LOD and billboards

For dense forests, the cheapest fix beyond MultiMesh is the billboard imposter:

1. Generate the tree mesh once at high polycount.
2. Render it from one angle to a transparent PNG (Godot's EditorScript can capture a viewport).
3. Use that PNG as a Sprite3D with billboard = enabled.
4. Swap from MeshInstance3D to Sprite3D at ~50m camera distance via Godot's VisibleOnScreenNotifier3D or a custom LOD script.

For a 200-tree forest, ~10 close trees are real meshes, 190 are billboards. Frame budget saved: ~80%.

Anti-patterns

• Generating "a forest" as one prompt. Returns a single fused mesh — useless for placement. Always one species per generation, then scatter.
• Regenerating the same species 5 times for variety. Generate 5 different species/states/colors for true variety; identical regenerations don't differ enough.
• High polycount on background organics. A 30k-tri rock used 50 times in the background tanks the frame rate. Cap distant organics at 2k.
• Ignoring MultiMeshInstance3D. 100 individual MeshInstance3D nodes = 100 draw calls. 100 instances of one MultiMesh = 1 draw call. Same visual result.
• Adding collision to every leaf and pebble. Player only needs collision on things the body can hit. Skip it for distant scenery and small ground litter.
• Using meshy (legacy). No reason to — trellis is faster and hunyuan is higher quality.

Edge cases

• Animated foliage (wind sway). Generate static here, then add wind sway via a vertex shader on the material — summer:vfx/shaders (when available). No animation rig needed.
• Underwater organics (kelp, anemones). Same flow; expect Hunyuan to add a "ground attachment" base unless you say floating, suspended in water.
• Branching meshes (vines, roots) come back too thick. Specify thin tendril, fine branches, or accept and scale Y down in the editor.
• Snow / ice / frozen variant. Add covered in snow, frosted, ice crystals to the prompt — works well on trees and rocks. For temperature variants of the same scene, generate the variant rather than retexturing.
• Crystal/glass organic. Mesh comes back opaque. Generate the geometry, then assign a StandardMaterial3D with transparency = ALPHA and emissive in the editor.
• Bones, skulls, dead trees. All work great — organic forgives them more than props would. Add weathered, sun-bleached for desert / tundra feel.

Fallback (no MCP)

1. Run prompts at the Summer dashboard or any 3D-gen web playground (Hunyuan, Trellis, Meshy).
2. Download .glb files into res://assets/organic/.
3. Build scatter scenes manually in Godot.

For totally free / offline alternatives: Quaternius (free stylized organics), AmbientCG (rocks + textures), Sketchfab free filter, Polyhaven (HDRIs + scans).

Handoff

After the organic models are scattered:

> Forest scatter ready: 3 species at res://assets/organic/, 100 instances each via MultiMeshInstance3D in ./World/Forest. Next: > - Wind shader (sway in breeze): summer:vfx/shaders when available, or hand-write a vertex displacement shader. > - Ground texture (grass beneath the trees): summer:asset-pipeline/asset-strategy Pipeline 2 for tileable ground. > - Lighting / fog (forest mood): summer:3d-lighting for ambient + directional sun + volumetric fog. > - Ambient audio (forest birds, leaves): summer:audio/ambient-bed. > - Hero props (a stump, a fallen log, a shrine): summer:3d-assets/prop-model for the hand-placed standouts.

See also

• summer:3d-assets/prop-model — for hand-placed standout pieces.
• summer:3d-assets/environment-kit — pair with this skill: kit pieces give the architecture, organic gives the natural softness.
• summer:asset-pipeline/asset-strategy — meta-router; ground textures and skyboxes go to Pipeline 2 / panoramic gen.
• summer:scene-composition — MultiMeshInstance3D scatter pattern.
• references/mcp-tools-reference.md — summer_generate_3d schema.

Source & license

This open-source skill is cataloged on AgentStack and links to its original source — we do not rehost the code.

• Author: SummerEngine
• Source: SummerEngine/summer-engine-agent
• License: MIT
• Homepage: https://summerengine.com/

Install and usage instructions live in the source repository linked above.