[VRChat] Light Probes and Reflection Probes: Brightness and Reflections for Moving Objects

You baked the room's lighting and got clean shadows on the floor and the walls. But the cup on the desk is still oddly dark.

The same goes for pickups, moving doors, and avatars. The walls are bright while the things standing in front of them look sunken.

This article sorts out why, then places Light Probes to fix the brightness of moving objects. We'll try metal reflections once too.

What You'll Learn

• Why only moving objects go dark
• How to place Light Probes, and what heights to aim for
• That a rebake is required after placing probes
• Reflection Probes, which put the room into metal

Start from a room you've already baked. If you haven't, build it in lighting and baking.

---

Burnt-in light can't be pasted onto moving objects

Baking burns light onto the surfaces of floors and walls. Put another way, it pastes a photograph made for things that don't move.

Moving things like cups and pens have no such photograph. So however bright the room is, they have no way to know how much light falls on them.

That's what Light Probes are for. Picture them as light meters hung in the air.

• Baked walls = a photo of the room pasted onto the wall
• Light Probe = a light meter hung in the air
• A moving prop = borrows the value from the nearest meter to light itself

With no meters at all, props end up with "only the sky's brightness, indoors" or close to pitch black. Bright walls with a sunken cup isn't a malfunction — it's this mechanism working as designed.

The roles split three ways. Lightmaps cover brightness on static surfaces, Light Probes cover brightness on moving objects, and Reflection Probes cover reflections on metal and glossy surfaces. Mixing them up means fixing the wrong thing.

Hands-On: Place Light Probes and rebake

Hang light meters in your baked room and confirm that prop brightness gets fixed.

1. Place a sphere to compare against

First, set up something where the change is visible.

Create a "3D Object → Sphere," name it ProbeTestBall, and put it around (0, 1, 0), midway between a bright area and a dark corner.

Don't set Contribute GI on this sphere. We want it excluded from the bake and treated as a moving object.

Press Play and look. The room is bright, but the sphere should be flat and dark. That's the state we're about to fix.

2. Place a Light Probe Group

Right-click empty space in the Hierarchy and choose "Light → Light Probe Group."

Pressing the Edit Light Probes button in the Inspector lets you edit the yellow points. You can't select points without pressing it. A common accident is trying to move points without it and shifting the whole group.

Eight points start out arranged in a cube. Build up from there.

1. Select one point, copy it with Duplicate Selected, and move it into position
2. Select a completed row and duplicate that
3. Change the height and make another tier

Duplicate Selected duplicates the points you have selected. With nothing selected, nothing gets added.

3. Decide where they go

Filling the room evenly isn't the goal. Place them where moving objects travel, and at boundaries where brightness changes.

For a small room, 12–20 points is plenty. Rough guidance:

Height	What it's for
Near the floor (5–20cm)	Props set on the floor, dropped items
Hand height (70–90cm)	Props on desks, held items
Head height (140–170cm)	Avatars themselves

Across the plan, put them at the room's center, under the lights, and in dark corners. Where brightness changes sharply (near a window versus the back of the room), place points on both sides of that boundary.

Delete any point buried in a wall or below the floor. Leaving them makes props and avatars passing nearby suddenly go dark. Check the Scene view from above and from the side.

Avoid laying them flat in a single tier. That can't capture vertical variation, so crouching and standing come out identically lit.

4. Rebake

This is the easy part to forget. Placing probes alone does nothing.

Open the Lighting window and press Generate Lighting again. Now each probe records the brightness at its location.

When the bake finishes, press Play and look at ProbeTestBall. Blending into the surrounding brightness means it worked.

Move the sphere between a bright area and a dark corner and confirm the brightness changes too. Values changing with position is the proof that probes are working.

Note that moving probes later also requires a rebake. Moving alone leaves the old values in place.

Reflection Probes handle reflections

Even with brightness fixed, metal and glossy surfaces still look wrong. They're reflecting the sky.

That's because without reflection information, Unity reflects the sky (the Skybox). Reflecting sky indoors doesn't read as metal.

To fix it, place a Reflection Probe.

1. Create "Light → Reflection Probe" in the Hierarchy
2. Put it at the center of the room, a little above eye level (around (0, 1.6, 0))
3. Confirm Type is Baked in the Inspector
4. Fit its area of effect (Box Size) to the room
5. Run Generate Lighting again

To check, set ProbeTestBall's material to Metallic 0.9 and Smoothness 0.8. Before baking the sky reflects; after, the room does.

Turning Box Projection on calculates the reflection along the box's shape, giving a reflection that reads as a room. Off, it reflects like distant scenery.

One Reflection Probe is enough. Add more only when the room is large, or when some areas differ wildly in brightness.

Common Pitfalls

• Placed probes but nothing changed → You haven't run Generate Lighting. Placing alone does nothing
• Some areas suddenly go dark → There are probes buried in walls or floors. Find and delete them with Edit Light Probes
• The sphere stays pitch black → Check whether Contribute GI is set on it. If it is, it's treated as a static object and won't use probes
• The sky reflects in metal → There's no Reflection Probe, or you haven't rebaked
• Points won't select → The Edit Light Probes button isn't pressed

Bonus: Good to Know Up Front

• Avatars are affected by probes too: A visitor's avatar is a moving object, so it looks dark without Light Probes. Always place them where people stand
• More points isn't automatically better: Each one adds bake time and data. A uniformly lit room needs few
• Interpolation ignores walls: Probes are linked in straight lines and interpolated, so probes on both sides of a wall leak the neighboring room's brightness. Place them room by room
• Reflection Probes cost too: Setting one to Realtime calculates every frame and gets heavy. Baked is plenty indoors
• Brightness and reflection are separate problems: "The prop is dark" is Light Probes, "the metal looks wrong" is Reflection Probes. Split by symptom

Summary

Baking alone doesn't light moving objects.

• Burnt-in light can only be pasted onto the surfaces of static objects
• A Light Probe is a light meter hung in the air. Moving objects borrow brightness from it
• Place them where moving objects travel and at brightness boundaries. Three height tiers, 12–20 points
• Nothing is recorded until you run Generate Lighting after placing them

The question that splits the symptoms is: "Is it dark, or is the reflection wrong?" Dark means Light Probes; reflections mean Reflection Probes.

Once the brightness is settled, add sound in BGM and spatial audio, or review the weight in making rendering lighter.