Isoplanar2D – 3D assets, strictly planar camera, iconic 2D look (Unity URP)

This package sets up a “2D-but-richer” pipeline: you author in 3D, render orthographically, and enforce a crisp, iconic style via toon ramps, optional matcaps, inverted-hull outlines, and a lightweight posterize pass. Camera moves are strictly isoplanar (pan/zoom only; no tilt/roll/orbit).

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0) Prerequisites

• Unity 6.x (URP)
• URP Forward Renderer asset assigned in Project Settings → Graphics
• A URP Renderer Data (e.g., ForwardRenderer) referenced by the URP Asset

Project switches (recommended):

• Disable TAA; use MSAA (2x–4x) for edges
• Disable SSAO and screen-space shadows for a cleaner graphic read
• Keep shadows hard or short-radius soft; low distance

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1) Camera Setup (Strictly Isoplanar)

1. Create an empty scene.
2. Select the Main Camera:
   • Projection: Orthographic
   • Rotation: (0,0,0)
   • Add IsoplanarCamera component.
3. (Optional) Use Cinemachine:
   • Add a Cinemachine Virtual Camera set to Orthographic.
   • Use Framing Transposer for follow, Confiner 2D for bounds.
   • Lock camera rotation to identity (0,0,0).

Axis:

• WASD pans (via Input axes).
• Mouse wheel zooms (clamped between minSize and maxSize).

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2) Parallax Layers

For any background/foreground group you want to drift subtly:

• Add Parallax2D to that GameObject.
• Assign cameraTransform (defaults to Camera.main).
• Set strength:
  • Background: negative (e.g., -0.2)
  • Foreground: small positive (e.g., 0.1)
• Keep Z locked in sensible tiers (e.g., -6, -4, -2, 0, +2, +4) to retain 2D read and deterministic sorting.

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3) Materials & Shaders

Toon Ramp

• Create a Material using Isoplanar/ToonRamp.
• Generate a ramp via Isoplanar2D > Generate Toon Ramp (256x1).
  • Assign Generated_ToonRamp.png to _RampTex.
• Tune:
  • _RampStrength (0→1) blends toon banding onto base.
  • _ReceiveShadows scales contribution from main light’s shadow map.
• Optional _MainTex supports flat UV color or low-frequency paint.

Matcap Toon (optional)

• Create a Material using Isoplanar/MatcapToon.
• Generate matcap via Isoplanar2D > Generate Simple Matcap (256x256).
• Assign to props/characters for a controlled “inked” highlight that doesn’t depend on scene lights.
• Use _MatcapStrength to mix with the base color/texture.

Outlines (Inverted Hull)

• Duplicate the mesh (or add an additional material slot).
• Assign Isoplanar/OutlineInvertedHull material to the back (lower index) slot, the main toon to the front (higher index).
• Tweak _Thickness for stable outlines; keep it above sub-pixel at target resolution.
• This method is robust in orthographic and avoids screen-space wobble.

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4) Posterize Post Pass (URP Renderer Feature)

1. Select your URP Renderer Data asset (e.g., ForwardRenderer).
2. Click Add Renderer Feature → PosterizeRendererFeature (appears if scripts compiled).
3. Set:
   • Shader: Hidden/Isoplanar/Post/Posterize (auto-assigned)
   • Steps Per Channel: 4–8 (fewer = bolder bands)
   • Injection Point: AfterRenderingPostProcessing (default)
4. Ensure camera is using this Renderer (check on the camera’s Renderer override if applicable).

Tip: Posterize works great with MSAA and no TAA, keeping silhouettes crisp without temporal ghosting.

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5) Lighting Discipline

• Use one Directional Light for the scene key (fixed azimuth).
• Prefer hard shadows; clamp distance to prevent crawl.
• If you need soft fill, add a dim secondary light or use environment lighting at low intensity.
• Keep materials low-specular; iconic looks degrade with glossy micro-highlights.

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6) Asset Production Rules

• Value bands: aim for 3–4 discrete lightness levels per palette.
• Textures: prefer flat color or large shapes; avoid micro-detail (it shimmers in ortho).
• Transparency: minimize; for compound sprites/props use SortingGroup and Z tiers to avoid sorting noise.
• Shadows: either use blob quads on a catcher plane or the toon ramp + main shadow map. Be consistent.

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7) QA Checklist

• Multiple resolutions: test 720p and 1080p with TAA off; verify no texture crawl.
• MSAA: 2x/4x acceptable cost on desktop; confirm on your floor GPU.
• Outline thickness: never sub-pixel at smallest target resolution.
• Ramp sanity: confirm no banding flicker as camera pans (use clamp wrap & point filter on ramp).

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8) Known Failure Modes (and fixes)

• Shimmer on thin details → remove micro-textures; raise mip bias (+0.5 to +1); reduce anisotropy; thicken forms.
• Muddy look → disable SSAO/TAA; increase posterize strength; reduce texture complexity.
• Transparency sorting → avoid overlapping alpha; quantize Z tiers; use SortingGroup.
• Outline z-fighting → increase outline thickness slightly or push mesh by normal; ensure outline renders before main (lower queue).

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9) Extending

• Add a LUT grading pass (3D LUT) for palette enforcement if desired.
• For characters, you can bake skeletal animation to sprite sheets for perfect pixel lock while keeping 3D layouts.
• If you must hint depth, switch to Perspective with FOV 5–10° but keep camera level and only pan/zoom → preserves isoplanar motion.

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10) Quick Start

1. Create new URP scene.
2. Add IsoplanarCamera to Main Camera (orthographic).
3. Add a few cubes/planes at Z tiers (-4, -2, 0, +2).
4. Generate Generated_ToonRamp.png, create a ToonRamp material, assign to meshes.
5. Add PosterizeRendererFeature to the Renderer.
6. Hit Play: pan with WASD, zoom with mouse; add Parallax2D to BG for drift.

You now have a 3D-authored, 2D-reading, strictly planar pipeline with bold, iconic rendering.