In this lesson, you will learn how to leverage Scene View debug modes to visualize complex lighting data and isolate performance bottlenecks in your rendered environment.
When your scene looks "off" or performance dips, it is often because the lightmap resolution is too high or your Light Probes are not sampling correctly. Instead of guessing, you can use the Scene View Draw Mode menu located at the top-left of the Scene window to peek under the hood of your rendering pipeline.
Visualizing Lightmap Density
If your frame rate drops during light-heavy sequences, the Lightmap Density mode is your first line of defense. By selecting it from the dropdown, Unity highlights your geometry based on the Lightmap Resolution set in your Lighting settings.
- Blue/Green areas: Healthy texel density.
- Red/Hot areas: These objects have unnecessarily high lightmap resolution.
Lowering the Scale In Lightmap property on the Mesh Renderer of these "red" objects can significantly reduce your VRAM usage and bake times without a noticeable loss in visual quality.
Inspecting Light Probe Influence
To verify how dynamic objects receive baked lighting, switch to the Light Probe visualization mode. This mode draws lines connecting the probes in your scene, creating a tetrahedral grid.
- If an object is moving through a massive void where no lines exist, it will not receive proper indirect lighting, causing it to look "popped" or detached from the scene.
- If you see excessive flickering, use this view to ensure your probes are placed densely enough near transition areas between indoor and outdoor zones.
Checking Shadow Map Coverage
Finally, use Shadow Cascades mode to see exactly how your shadow maps are distributed. If your "near" cascade is too small, your shadow quality will suffer as the camera moves. Conversely, if your far cascade is too large, you are wasting rendering power on distant shadows that the player can barely see.
By cycling through these modes, you transition from subjective "artistic" adjustments to objective, data-driven optimization.
Key Takeaway: Use the Scene View Draw Modes to visually audit your lightmap texel density and probe distribution, ensuring you only allocate performance budget where it is visually necessary.