Inference and alignment guides

While you're drawing a wall, a tape dim, or any other measured line, the editor watches for moments when your cursor lines up horizontally or vertically with something already on the plan. When it sees an alignment, a thin purple line appears from the reference point to your cursor — and your cursor snaps onto that alignment. This is inference, and it's the fastest way to stay aligned without dropping a guide for every reference.

What you see

When the cursor approaches an alignment, the following appears:

• A thin purple line from the reference point to your cursor (horizontal if you're aligned in Y, vertical if you're aligned in X).
• A small purple bulge at the reference point so you know which entity the alignment is coming from.
• Your cursor snaps onto the alignment line, locking the Y (for horizontal) or X (for vertical).

If your cursor is near two reference points at once — one in X, one in Y — the lines combine and your cursor snaps to the intersection of both alignments. That's the high-confidence corner snap: you're aiming for the spot where two existing features cross.

What can trigger alignment

Inference treats the following as alignment sources:

• Wall endpoints — both ends of every wall in the active room.
• Fixture corners — the four corners of every fixture's bounding rectangle, rotated to match the fixture's angle.
• Tape dim endpoints and measurement marks — both ends of every tape dim, plus visible measurement marks dropped by the tape measure tool. Measurement marks only feed inference when they're visible (the Measurement Marks layer is on).
• Pin guides — point-style guides.
• Opening jambs and centres — both edges of every door, window, and cased opening, plus the centre point of each.

Each source can be toggled on or off independently in Settings → Inferences, and you can tune the sensitivity bucket (low / medium / high). Expert-tier filters let you exclude small walls and tiny fixtures so they don't add noise to the alignment list.

When inference fires vs. snap-to-target

Inference and the snap engine are two different layers. Snap pulls your cursor onto an entity directly — onto a wall endpoint, an opening jamb, a guide. Inference pulls your cursor onto an alignment with an entity — same Y as an endpoint, same X as a fixture corner — without putting you on the entity itself.

In practice, both layers run together. A typical wall draw might snap to a wall endpoint to start, infer horizontal alignment with a fixture corner while the cursor rubber-bands, and snap onto a guide line at commit. All three happen automatically without any explicit mode switch.

Turn inference off

In Settings → Inferences, the master Enable Inferences toggle is the off switch. With it off, no purple alignment lines appear and the cursor doesn't snap to alignments — only direct snap targets still pull it.

Per-source toggles in Settings let you turn off alignment from walls, fixtures, dim endpoints, pin guides, or openings independently. Minimum-size filters can exclude tiny walls and small fixtures so they don't add noise.

Override for one click

Hold Ctrl while moving the cursor on desktop to bypass inference for that one point. The alignment lines hide and the cursor moves freely. Release Ctrl to bring inference back. Useful when an aggressive alignment keeps grabbing your cursor away from where you want it.

Why this matters

In residential drafting, half the work is making sure the new geometry lines up with what's already there — a partition wall lines up with a window, a vanity centres on a wall, a fixture aligns with a fixture across the room. Inference makes those alignments automatic without dropping a guide for every relationship. Use guides for permanent references you want documented; use inference for the dozens of small alignments per drawing that don't need to be saved.

Tips

• The purple bulge at the reference point is the cue that tells you which entity the alignment is coming from. Look at it before committing — sometimes the alignment is real but the reference is wrong (a stray fixture corner instead of the wall you meant).
• When two alignments meet at an intersection, the cursor lands on the intersection. The alignment lines from both references show up at once — that's the strongest snap.
• Drop a quick guide for any alignment you'll need repeatedly. Inference doesn't keep state — every time you start drawing, it recalculates from the current scene.
• For more control, open Settings → Inferences to pick exactly which sources should feed inference. Turning off fixture inference is common when you're laying out walls first and don't want existing fixture corners pulling the cursor around.
• The Ctrl bypass on desktop is point-by-point, not a mode. Release the key and inference resumes immediately.