The chain
$14.621 for the whole chain, at each model’s list price:
- Kit concept sheet: $0.053 ($0.053 per image)
- One picture per piece x 24: $0.96 ($0.04 per image, 24 jobs)
- 3D model per piece x 24: $13.608 ($0.525 per model, 24 jobs)
summer api estimate <model> --input '<json>', or POST /v1/estimate with the same body as the job. Prices come from GET /v1/models and change only when the provider’s price does.
The chain above is a 24-piece kit. Most of the cost is the 3D step, which is why every piece is checked as a cheap picture first.
Before you start
Sign in once, so your agent or your terminal can run jobs on your Summer account:- The style sentence. One sentence, no more: “Stylized hand-painted low-poly game art, chunky readable shapes, muted greens, warm grey stone and dark wood.” It goes into every prompt in this guide, word for word. When a piece does not match later, the first thing to check is whether this sentence drifted.
- The piece list. Every piece, one line each: “broken pillar”, “stone archway”, “wooden crate with iron corners”. Split big things into parts the player can reuse.
- The grid. Pick it before anything is made: 1 m for tight dungeons and corridors, 2 m for houses and taverns, 4 m for halls and outdoor ruins. Every wall and floor piece fits the grid.
Step 1: one concept sheet that sets the style
A concept sheet shows six to ten pieces of the kit side by side in one picture. Because one picture holds them all, they share one palette, one light and one level of detail. That picture becomes the style reference for every piece after it.- Name each piece, and ask for clear empty space between them.
- “All pieces at the same scale” gives you a first idea of relative sizes.
- A white background, even light, no ground plane. The sheet is a reference, not a scene.
- No text, no labels. Labels end up painted into the pieces.
fileUrl once you like it.
Step 2: a clean picture of each piece
Image-to-3D reads one object at a time. A sheet with eight pieces would become one fused lump. So edit the sheet once per piece:referenceImageUrl is the sheet, and the prompt names one piece and repeats the style sentence.
What image-to-3D needs from each picture:
- One whole object, centered, nothing cropped.
- Three-quarter view from slightly above. The model sees the front, one side and the top, so it guesses less.
- White background, even light, no cast shadow, no ground. Shadows and floors become geometry.
- Open where it should be open. Say “empty archway, you can see through it” or “pot with an open top”. Models close holes by default.
imageUrls (two to four views of the same object) in step 3 instead of imageUrl.
Step 3: a light 3D model per piece
Send each picture’sfileUrl as imageUrl. Two fields matter for a kit:
assetIntent: "object"treats the picture as a prop, not a character.targetPolycountsets about how many polygons the mesh gets. Without it, the model decides, and a background crate can come back heavy enough to slow the level when you place fifty of them.
running, and you read GET /v1/jobs/{id} until state is done (jobs).
Polygon budgets that work for a kit:
Keep the pieces of one kit within about twice each other’s budget. A dense pillar next to a plain wall reads as “this pillar is special”, when it should read as part of the set.
Other models for this step. Rodin 2.5 Fast makes light meshes up to 20K faces for background props at a low price ($0.10 per model). Hunyuan 3D Rapid is for blockout meshes to check layout and scale before the final pieces ($0.225 per model). Tripo P2 builds clean quad meshes at a controlled face budget when an artist will edit them ($1.10 per model). Trellis 2 is a good second opinion on thin shapes, such as a lantern post or a spear, that come back too thick. For one sculpt-level hero piece, Hi3D V3.0 has the finest detail.
Make the whole kit in batches
A kit is 20 to 100 pieces. Send it as two batches: all the pictures, then, after you have checked them, all the 3D models. A batch takes up to 500 jobs, is priced when it arrives and runs all or none, so you know the total before anything starts (batches). The picture batch is one line per piece, each with the sheet as reference and the same style sentence:result.assets[0].fileUrl. Turn them into the 3D batch, one line per picture, in the same order:
art/kit/pictures and delete the line of any piece you do not want from kit-models.jsonl. Set a different targetPolycount on the lines for hero pieces and small props, and add a title to each line to name the asset in your library. Each account runs 10 jobs at once at the start and more as it buys credits; the rest of a batch waits its turn in order, and a waiting job is not an error.
Put it in your game: scale and placement
Generated models are not at real-world size, and their origin is wherever the model put it. Fix both once per piece, and the kit snaps together.- Scale to the grid. On a 2 m grid, a wall section is 2 m wide and about 3 m tall, a floor tile is 2 by 2 m. A crate is about 0.8 m, a door about 2 m, a bench about 0.5 m high. Measure the mesh’s bounding box and scale it to the target.
- Move the origin. Bottom-center for props and floors, so they sit on the ground at y = 0. Bottom corner for walls, so they snap edge to edge on the grid.
- Turn on grid snapping at the grid size, and rotate walls in 90 degree steps.
- Collisions. Walls, floors and large props need a simple collision shape, a box or two, not the full mesh.
assetId, or drop the files into res://assets/kits/shrine/. A GLB imports as a scene: instance it in the level, do not assign it as a mesh. Make one kit scene that holds one of every piece side by side on the grid, and build levels from it. For hundreds of small repeats, such as stones or grass tufts, use a MultiMeshInstance3D. The environment-kit skill stages the kit and checks scale and pivots for you; prop-model makes a single hero prop; organic-model makes rocks and plants that break up the straight lines.
Any other engine. The GLB is standard glTF 2.0, Y up. Apply the scale and origin fixes in your import settings or in a modeling tool, then save each piece as a reusable prefab or scene.
Flat walls and floors do not always need a 3D model. A box with a good tiling texture is lighter and snaps perfectly. The seamless textures guide makes those, in a style that matches the kit if you send the concept sheet as the reference.
Common problems
Questions
Can I skip the pictures and go straight from text to 3D? Yes:kind: "text-to-3d" with a prompt works for one-off props. For a kit, the pictures are what keep the style the same, and they let you check every piece cheaply before the 3D step.
Can I use my own concept art? Yes. Upload it (send a picture) and use its fileUrl as the reference in step 2, or as imageUrl in step 3 if it already shows one piece on a plain background.
Can I use the kit in a commercial game? Yes. Every model on the Summer API allows commercial use of what it makes.
Do I need a plan? No. Jobs are paid from your paid Summer credits, your plan’s credits or a top-up. Each connected agent has its own spend limit in Settings > Connected apps.