Visual Density Heatmap

Verify placement density and performance hotspots instantly with a SceneView grid overlay

High asset density is the leading cause of frame rate drops in Unity environments. Over-clustering prefabs leads to severe GPU overdraw, excessive draw calls, and physics collision lag. However, identifying these performance-heavy hotspots visually in a complex 3D scene is incredibly difficult.

The Visual Density Heatmap provides an instant, interactive diagnostic overlay directly inside the SceneView. By partitioning your scene bounds into a grid and analyzing object density, it color-codes regions so you can spot dead zones and over-scattered zones immediately.

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Technical Architecture

The heatmap engine runs a spatial partitioning grid check across the active scatter boundaries.

Grid Partitioning & Hotspot Analysis

1. Spatial Bounds Query: The system calculates the world-space bounding box containing all objects under the active scatter parent.
2. Grid Baking: It partitions this bounding box into a 2D grid (default is $32 \times 32$ cells).
3. Density Calculation: For each cell, it calculates the number of active scatter instances overlapping the cell’s horizontal boundaries: \(\text{Cell Density} = \frac{\text{Objects in Cell}}{\text{Cell Area}}\)
4. Color-Code Mapping: Cells are rendered in the SceneView using a color ramp based on target density thresholds:
   • Blue (Low / Under-saturated): $0\% - 20\%$ of expected density. Indicates barren ground or failed raycasts.
   • Green (Optimal / Balanced): $21\% - 70\%$ of expected density. Safe range for gameplay performance.
   • Yellow (High Warning): $71\% - 90\%$ of expected density. Performance warning—LOD setups recommended.
   • Red (Critical / Over-saturated): $>90\%$ of expected density. Hotspot zone containing extreme draw calls or overlapping colliders.

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Editor Window Interface

Access this window via Tools → Decnet → Visual Density Heatmap. The window displays real-time statistics and drawing options:

• Grid Resolution: Configures the subdivision density (from $8 \times 8$ up to $64 \times 64$ cells).
• Overlay Opacity: Adjusts the transparency of the SceneView grid tiles ($0\% - 100\%$).
• Analyze Scene: Bakes the active scene layout and updates the density metrics.
• Auto-Refresh: If enabled, the heatmap dynamically updates as you paint, scatter, or erase objects.
• Hotspot Statistics Panel:
  • Total Bounds Area: Total square meters analyzed.
  • Average Density: Average objects per square meter.
  • Peak Cell Count: The highest number of objects crammed into a single cell.
  • Performance Alert Index: A color-coded status bar highlighting whether the scene is optimized, moderate, or critically heavy.

[SceneView Heatmap Visualizer]
┌───┬───┬───┬───┐
│ B │ G │ G │ Y │   B = Blue (Sparse)
├───┼───┼───┼───┤   G = Green (Optimal)
│ G │ R │ R │ G │   Y = Yellow (Dense)
├───┼───┼───┼───┤   R = Red (Over-saturated Hotspot)
│ G │ G │ B │ B │
└───┴───┴───┴───┘

[!WARNING] Keep the heatmap overlay closed or disable Auto-Refresh when scattering over 100,000 objects. While the partition algorithm is highly optimized, rendering tens of thousands of transparent Handles in the SceneView every frame can impact editor response times.

[!TIP] If you see large red zones in the heatmap, run the Static Mesh Combiner on those specific regions or reduce the Density slider in the main scatter window before re-generating.