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T1KTheOneKit

t1k:unity:dots-rendering:perspective-2d-topdown

FieldValue
Moduledots-rendering
Version2.1.7
Efforthigh
Tools—

Keywords: 2D, DOTS, perspective, top-down

How to invoke

Section titled “How to invoke”
/t1k:unity:dots-rendering:perspective-2d-topdown

DOTS Perspective: 2D Top-Down

Section titled “DOTS Perspective: 2D Top-Down”

When This Skill Triggers

Section titled “When This Skill Triggers”
  • 2D top-down, orthographic camera, sprite rendering, quad mesh, Y-sorting
  • SpriteAnimationSystem, SpriteColor, SpriteSheetUV, DeathFadeSystem
  • URP/Unlit cutout, alpha clip, flat rendering

Key Concepts

Section titled “Key Concepts”
  • Simulation: XZ plane (always). All navigation, physics, AI operate on XZ
  • Presentation: Camera looks down -Y axis. Entities are flat quads in XZ plane
  • No coordinate remapping — simulation coords = visual coords (unlike side-view)

Camera Setup

Section titled “Camera Setup”
  • Orthographic, rotation (90, 0, 0), position (0, height, 0)
  • farClipPlane = CameraHeight + 50f (must exceed camera Y position)
  • Camera uses Cinemachine 3.x (CinemachineCamera + CinemachinePositionComposer + CinemachineConfiner2D + CinemachineImpulseListener)
  • Bridge: CinemachineCameraBridge MonoBehaviour reads CameraTarget singleton → proxy Transform → CinemachineCamera.Follow
  • Auto-zoom: CinemachineAutoZoom MonoBehaviour queries alive DOTS entities → XZ AABB → cam.orthographicSize
  • CinemachineConfiner2D: BoxCollider2D must be on main scene (not SubScene)
  • → See references/camera-2d-topdown-guide.md and unity-cinemachine skill

Rendering

Section titled “Rendering”
  • Quad mesh in XZ plane: vertices at y=0, spanning (-0.5, 0, -0.5) to (0.5, 0, 0.5)
  • Shader: Universal Render Pipeline/Unlit — no lighting needed for top-down
  • Material mode: Opaque + AlphaTest (cutout) — enables SRP Batcher batching
  • Team color: White base material + per-entity SpriteColor [MaterialProperty("_BaseColor")]
  • Shadows: ShadowCastingMode.Off, receiveShadows = false on all quads -> See references/rendering-2d-topdown-guide.md
Section titled “Navigation”
  • NavigationAuthoring.EnableGrounding = false — skip DOTSGroundingSystem (no Y physics)
  • RangedAttackAuthoring.ArcHeight = 0 + IsFlat = true — flat 2D projectile trajectory
  • Standard XZ NavMeshSurface on ground plane; NavMeshObstacle.carving = true for obstacles
  • MappingExtent must be proportional to arena size (200x200 arena needs ~50)

Animation

Section titled “Animation”
  • SpriteAnimationAuthoring for sprite sheet UV animation (FrameCount, Columns, FPS)
  • SpriteAnimationSystem advances frames via SpriteSheetUV [MaterialProperty("_BaseMap_ST")]
  • DeathFadeSystem lerps SpriteColor.Value.w (alpha) based on DeathAnimation.Remaining
  • Static sprites: set FrameCount = 1, FPS = 0

Common Patterns

Section titled “Common Patterns”

Quad Mesh Creation (XZ Plane)

Section titled “Quad Mesh Creation (XZ Plane)”
mesh.vertices = new[] {
    new Vector3(-0.5f, 0f, -0.5f), new Vector3(0.5f, 0f, -0.5f),
    new Vector3(-0.5f, 0f,  0.5f), new Vector3(0.5f, 0f,  0.5f),
};
mesh.triangles = new[] { 0, 2, 1, 2, 3, 1 };
mesh.normals = new[] { Vector3.up, Vector3.up, Vector3.up, Vector3.up };

Cutout Material Setup

Section titled “Cutout Material Setup”
mat.SetFloat("_Surface", 0f);     // Opaque
mat.SetFloat("_AlphaClip", 1f);   // Enable cutout
mat.SetFloat("_Cutoff", 0.5f);
mat.SetOverrideTag("RenderType", "TransparentCutout");
mat.renderQueue = (int)RenderQueue.AlphaTest;
mat.EnableKeyword("_ALPHATEST_ON");
mat.enableInstancing = true;

Gotchas

Section titled “Gotchas”
#IssueFix
1Camera farClipPlane < CameraHeight = invisible troopsSet farClipPlane = CameraHeight + 50f
2Transparent materials defeat SRP Batcher (608 batches)Use Opaque + AlphaTest cutout (28 batches)
3DetectionRadius < spawn gap = troops stand idleSet DetectionRadius > half the spawn gap distance
4Prefab regeneration wipes BDP treesAlways run “Build Behavior Trees” after “Create Unit Prefabs”
5while not if for SpriteAnimation frame advanceLarge deltaTime can skip multiple frames
6CinemachineConfiner2D references SubScene colliderBoxCollider2D for confiner MUST be in main scene
7Camera shake saturates with 500+ unitsHundreds of hits/frame × 0.03 trauma = instant max. Remove CinemachineImpulseListener from camera or set CameraTrauma.MaxIntensity=0

Cross-References

Section titled “Cross-References”
  • dots-ecs — ECS fundamentals
  • dots-rpg — SpriteAnimation, SpriteColor, SpriteSheetUV components
  • dots-graphics — Rendering fundamentals, MaterialProperty overrides
  • agents-navigation — Pathfinding, NavMesh setup
  • dots-performance — Batching, draw call optimization
  • unity-cinemachine — CinemachineCameraBridge, Confiner2D, impulse patterns

Reference Files

Section titled “Reference Files”
FileCoverage
references/rendering-2d-topdown-guide.mdSprite setup, materials, quad mesh, cutout vs transparent
references/camera-2d-topdown-guide.mdOrthographic setup, auto-zoom, bounds tracking