Canvas · Advanced · Tutorial 3 of 3
Changing the resolution keeps your paint.
It deletes every undo that could have saved it.
The two tiers below this one both end with a finished texture, so this one is not another pass of painting. It is the short list of decisions that cost nothing before your first stroke and cannot be taken back after it — each of them silent, each of them settled by something you do in the first minute of opening a model.
What this tier is for
Everything in First Coat and The Canvas Bench is recoverable. You can repaint a layer, delete it, change a material, step back. This page is about the handful of things that are not — where the tool does exactly what it was asked and quietly takes something away in the process.
None of these are bugs. They are consequences, and every one of them is cheap to avoid if you know about it before you start.
Before you start
Have a multi-part model to hand — something with a body and a separate piece, not a single merged mesh. Half of this page is about what happens when a model arrives in more than one part.
Read the log strip. Canvas warns about exactly one of the problems here and is silent about the rest, and knowing which is which is most of the skill.
Changing the texture resolution clears your entire undo and redo history.
Not trims it — empties it. Your paint survives, resampled to the new size, but every step you could have gone back through is gone the moment the resolution changes, and nothing in the window mentions it. Choose the resolution when you open the model, not when you are halfway through.
Texture resolution
Resolution is a decision
A new model opens at 1024 × 1024. The resolution field will
take anything, and quietly holds you between 64 and 8192 — ask for
16 and you get 64, ask for 99999 and you get 8192.
Changing it does three things, and only the first is the one you asked for.
| What happens | Detail | Recoverable? |
|---|---|---|
| Every layer is resampled | Through a Lanczos resize, colour and mask alike, at the new size. | Paint survives — but a trip down and back up does not return what you had. |
| The curvature bake is discarded | It was computed for the old size, so it is thrown away rather than stretched. | Yes — re-bake it. |
| Undo and redo are emptied | Both stacks are cleared outright. | No. This is the one that costs you. |
The combination is what makes it sharp. Going from 2048 down to 1024 and back up leaves you with paint that has been through two resamples and no history to undo it with, because the first change threw the history away before the second one happened.
2048 — large enough for most
props, and it saves you the one change that hurts.Multi-part models
The atlas is all-or-nothing
When a model arrives in several parts, Canvas merges them into one paintable mesh and gives each part its own cell of the texture, so that painting the hull cannot put paint on the turret. That is the intent. It happens only if every part has UVs.
Figure 01 — why one bad part ruins a good one The decision is taken once, when the model is merged at load. Nothing you do afterwards re-runs it.
So the symptom to recognise is paint appearing somewhere you did not paint. It is not a brush problem, a layer problem or a mask problem, and no amount of care with the brush will avoid it — the two parts are genuinely sharing the same square of texture, and every stroke is landing on both.
The cause is always the same: at least one part of the model came in without UVs. The fix is not in Canvas. Unwrap the offending part in your modelling tool and re-import, because the merge that decided this happened when the file was loaded.
Drill01
Recognise paint-through in ten seconds
- Load a multi-part model and pick a bold colour.
- Put one stroke on the largest part.
- Orbit and look at every other part.
Done when you make this the first thing you do after loading any model with more than one piece.
Drill02
Prove the all-or-nothing rule
- Export a model with UVs on every part; load it; confirm no bleed.
- Strip the UVs from one small part; re-export.
- Load it again and repeat drill 01.
Done when you have seen one part's omission change the behaviour of a part you never touched.
Bakes
What the bakes need
The baking buttons — ambient occlusion, and height into normal — read the mesh rather than your layers, so they have a requirement the brush does not: the model must be UV mapped.
The good news, and it is worth stating because so much else on this page is silent: a bake that cannot run refuses instead of producing a wrong result. Ask for ambient occlusion on a mesh with no UVs and the tool declines and tells you it needs a UV-mapped mesh. It does not hand you a flat or garbled AO map that you then paint on top of for an hour.
Loading a mesh without UVs also puts a warning in the log — the one warning this page's problems get. If you are ever unsure which situation you are in, that line is the fastest answer.
| Symptom | What it means | Fix |
|---|---|---|
| Bake AO does nothing and says it needs a UV-mapped mesh | Honest refusal. The mesh has no usable UVs. | Unwrap and re-import. Nothing was damaged. |
| Paint lands on parts you did not touch | Atlasing was skipped because a part lacks UVs. | Unwrap that part and re-import — it is decided at load. |
| Undo greyed out after changing resolution | Working as designed. Both stacks were cleared. | Nothing to recover. Set resolution before painting next time. |
| Smart-material wear looks wrong after a resolution change | The curvature bake was discarded with the old size. | Re-bake curvature, then re-apply the material. |
| Detail looks soft after going up in resolution | Resampling invented no detail; it only enlarged what was there. | Repaint the affected passes at the new size. |
The habit
A preflight worth doing
Everything above collapses into a short routine you run once, immediately after loading a model and before the first stroke. It takes about a minute and it is the whole point of this tier.
Before the first stroke
- Read the log strip for a UV warning on load. it is the only one of these problems the tool announces
- Put one bold stroke on the biggest part and orbit the whole model. ten seconds, and it is the only reliable test for paint-through
- Press Bake AO once. if it refuses, the mesh is not UV mapped and nothing else is worth starting
- Set the texture resolution now, and do not change it again. free before the first stroke; costs your entire history afterwards
- Only then start layering. everything from here is recoverable, which is what the two tiers below teach
Ladder complete
What you now know
Check yourself
- Texture resolution is clamped to
64–8192and defaults to1024. - Changing it empties undo and redo. Paint is resampled and survives; history does not.
- A resolution change also discards the curvature bake, so smart-material wear needs re-baking.
- Multi-part models are atlased into separate UV cells only when every part has UVs.
- One UV-less part collapses the whole model into a single shared cell, and the symptom is paint appearing on parts you did not touch.
- That decision is taken at load, so the fix is in the modelling tool and a re-import.
- Bakes refuse honestly without UVs rather than producing a wrong result, and a UV-less mesh is warned about in the log.
- The preflight is one stroke, one bake and one resolution choice, before anything else.
That closes the Canvas ladder. First Coat gets a texture finished, The Canvas Bench makes it good, and this page keeps the first two from being wasted on a model that was never going to work. If you would rather take the tool end to end in one sitting instead of three, Canvas Accelerated on the site covers the same ground by a different route.