Remember yesterday’s “TERRAIN NOT RENDERING” commit? Turns out the terrain was rendering just fine. We were looking at the wrong problem.

The misdirection

The symptom: after pressing Start on the title screen, the player appeared in a void. No terrain visible, no rooms, nothing. Natural conclusion: the terrain generation is broken. We’d just built the GeometryDef pipeline and changed how terrain generation was invoked, so it made sense that something in that chain was failing.

We spent the morning adding debug output to every stage of the terrain pipeline. Checking Terrain:FillBlock() calls — they were executing. Checking region boundaries — they were correct. Verifying terrain material selection — working fine. The terrain was being generated, and printing its voxel count confirmed it existed in the workspace.

So why couldn’t we see it?

The actual bug

The player was spawning outside the map. Way outside. Hundreds of studs away from the dungeon. The camera was pointed at empty sky because the character was nowhere near any generated geometry.

The cause: a data structure mismatch in the spawn point handling. The new GeometryDef pipeline stores spawn data as a structured object:

layout.spawn = { position = {x, y, z}, roomId = 1 }

The RegionManager’s teleportation code was reading it as a flat array (the old format):

local x = layout.spawn[1]  -- nil
local y = layout.spawn[2]  -- nil
local z = layout.spawn[3]  -- nil

Three nil values. In Lua, Vector3.new(nil, nil, nil) doesn’t error — it silently produces Vector3.new(0, 0, 0). The player teleported to the world origin, while the dungeon was generated hundreds of studs away at its normal position.

The fix

-- Before (old flat array format)
local x = layout.spawn[1]
local y = layout.spawn[2]
local z = layout.spawn[3]

-- After (new structured format)
local x = layout.spawn.position[1]
local y = layout.spawn.position[2]
local z = layout.spawn.position[3]

That’s it. Three .position insertions. The terrain was always there. The player just wasn’t looking at it.

Why this class of bug is worth writing about

This is a pattern we’ve hit multiple times and will hit again: the symptom is far from the cause. “Terrain not rendering” was a perfectly accurate description of what we observed. It sent us straight to the terrain pipeline, where we spent hours verifying code that was working correctly.

The actual bug was in player positioning — a completely different system, in a different file, running at a different time. The connection between “spawn position is wrong” and “I can’t see the terrain” requires the non-obvious insight that the camera follows the player, and if the player is at (0,0,0) while the dungeon is at (500, 0, 300), there’s nothing to see.

Debugging rules we’re reinforcing:

  1. “I can’t see X” doesn’t mean X doesn’t exist. Check the camera first. Check the player position. Use workspace:FindFirstChild() to verify the thing actually isn’t there before assuming it wasn’t created.
  2. Silent nil propagation is Lua’s sharpest edge. table[key] returns nil on missing keys without error. That nil flows through arithmetic (nil + 3 errors, but Vector3.new(nil,nil,nil) doesn’t) and produces plausible-looking but wrong results.
  3. When you change a data structure, grep for every consumer. We changed the spawn format in the GeometryDef pipeline but didn’t update the RegionManager that reads it. This is the kind of thing that type systems catch — Luau’s type annotations would have flagged this at edit time.

The dungeon is playable again. The GeometryDef pipeline works end-to-end. Onward.