qhenshaw/unity-model-icon-renderer

Item icons rendered from 3D models

Turn the game's own prefabs into consistent icon sprites from code: an isolated preview scene, an orthographic camera with three directional lights, a pose chosen per model, a 2× supersampled render, premultiplied downsample, and a dark outline so icons read on any background. Re-runnable - regenerate whenever art or item shapes change.

Workflow

1. Check the pipeline. The template targets URP (UniversalAdditionalCameraData). For Built-in, delete that block; for HDRP, use HDAdditionalCameraData and disable post-processing the same way.
2. Copy templates/Editor/ModelIconRenderer.cs into an editor-only folder/asmdef (references URP runtime if using an asmdef) and rename the namespace.
3. Decide the mapping from game data to jobs: which prefab represents each item, its cell footprint (1×1 for plain icons; the item's grid shape for grid inventories), and the output path. Keep that mapping in the project's content code, not in the renderer.
4. Call ModelIconRenderer.RenderBatch(jobs) from a menu item or the content build step, then assign the resulting sprites to the item data (AssetDatabase.LoadAssetAtPath<Sprite>(path)), SetDirty, SaveAssets. PNGs are imported as sprites (alpha is transparency, no mipmaps).
5. Look at every icon with scripts/icon_sheet.py and fix outliers per item (see Review loop) rather than tweaking the global heuristics.
6. Commit the PNGs via Git LFS. Don't commit icons rendered from licensed art to public repos.

How the pose is chosen

• Elongated models (longest axis > 1.6× the middle one: swords, staffs, arrows, wands) are laid along the slot's long axis - vertical in tall slots, horizontal in wide ones, diagonal in square slots - then spun 25° around that axis so the side faces the camera.
• Compact models (gems, potions, books, chests) start from an upright 3/4 view, then a sweep of yaw (−90…90), pitch (−50, −25, 0) and roll (0…135) renders a tiny probe and keeps the view with the most silhouette pixels. Pixel coverage rather than bounds avoids thin diagonals winning; dead-on views are penalised 7% because they look flat; the automatic pose gets a 10% bonus so it's only replaced by a clearly better view.
• Compact model in a long slot (coverage < 30%, slot ≥ 3:1): copies are tiled along the slot with slight rotation/scale variation (three shards in a 1×3 slot) instead of one tiny model.
• Facing: most packs (Synty included) author props facing +Z; the camera looks along +Z, so models get a 180° yaw first (Options.facingCorrection). Change it if a pack faces another way.

Review loop

Never trust a batch you haven't looked at. One sheet catches what a hundred log lines won't.

1. Sheet: python scripts/icon_sheet.py <icon_folder> sheet.png --match ^Armor_ Shield --strip-prefix, then view the image. Icons keep their aspect ratio, so a 3×1 item shows as a strip, as it will in the grid.
2. Classify each bad icon - the fix differs:
   • Side-on / lying down / back facing camera → pose it with rotationOverride. It is applied as Euler(override) * facingCorrection, so (0,0,0)-ish values mean "as authored, facing the camera": small tilts like (-5, 15, 0) give an upright 3/4 view. (0, 180, 0) shows the back. Zero means "auto", so use a tiny non-zero value if you want the authored pose exactly.
   • Edge-on flat thing (shield, plate, coin) → the prefab usually has a rotated child (weapon display prefabs often rotate the mesh 90° on X so it lies flat in-game). Log the child's localEulerAngles before guessing; cancel it in the override and add a roll to lay the long side along the slot, e.g. (0, 90, 80) for a flat oval shield in a 3×1 slot.
   • Wrong silhouette for the slot (a tall thin model in a square slot: training dummies, armor stands, banners on poles) → no rotation fixes that; swap the model.
3. Audition replacement models in one render: temporarily point several existing items at candidate prefabs (item.iconModel = candidate, zero override), render, sheet, pick. Then put the winners in the content code - if the content build re-assigns models on every run, the temporary assignments are overwritten anyway.
4. Record poses in the content code, not only on the assets, so a rebuild with "overwrite data" keeps them. Apply a recorded pose only when the item has none of its own, so hand-tuned poses in the Inspector survive.
5. Re-render and re-sheet until every icon reads at a glance.

Good model sources for wearables: static modular-character parts (e.g. Synty Modular Fantasy Hero Characters_ModularParts_Static/Chr_Torso_*_Static) make far better chest-armor icons than props such as armor stands or training dummies - they fill a square slot and read as "armor" immediately. Character attachment prefabs (helmets, shoulder pads, capes) work well for the smaller slots. Static parts use the pack's ordinary texture material, so they convert to your shader like any prop.

Gotchas

• Preview scenes have no environment lighting or skybox - without the fill and rim lights, the side away from the key light renders black.
• Post-processing and MSAA break alpha. Disable post on the icon camera (tonemapping/bloom write alpha = 1) and supersample instead of MSAA.
• Set cam.scene = previewScene or the camera renders the open scene too.
• Strip colliders, disable Animators, particle/trail/line renderers on the instance - VFX children and bind-pose animators otherwise inflate bounds or show up as smears.
• Premultiply when downsampling, or transparent edges pick up dark fringes from the clear colour.
• Skinned characters render in bind pose (T-pose); give them a rotationOverride or a posed prefab variant.
• Palette-textured low-poly models look grey if their palette textures have mipmaps (see the unity-asset-pack-extraction skill).

Files

• templates/Editor/ModelIconRenderer.cs - RenderBatch(IconJob[], Options), IconJob(model, cells, pngPath, rotationOverride), menu Tools > Icons > Render Selected Prefabs (1×1 icons into an Icons/ folder next to each prefab).
• scripts/icon_sheet.py - labelled contact sheet of rendered icons, filterable by name (needs Pillow).