Describe the tilemap memo and what it saves per frame

Tilemaps gets the measurements under The cost of outlined cells. Architecture lists tilemapMemo in the model modules.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Architecture.md

@@ -73,7 +73,7 @@
 
 ```
 web/index.html         Vite source page (dev)            index.html   built page (generated, served)
-src/core/model/        Project (object holders), Asset + AssetTypes, SceneObject, Properties (value types), hierarchy, walk (generic parent/child walks), instance (container content resolved from its template), usages (where an asset is used), container (the cycle guard), placement (what may be dropped where), texture (frames, the slice grid, a frame's collision outlines), frameOutline (#193: a frame's outlines as a collider wears them, centred, a pixel to a unit, cut into pieces once per drawn list), traceCollision (#161: a frame's outlines read off its picture — the pixels from an alpha threshold on are solid, each 4-connected island is walked round along the pixel edges and cut down to a few corners without ever crossing itself; crumbs below 1 % of the frame drop out), generated (pictures that are drawn rather than uploaded, #185: the key `gen:<assetId>@<revision>`, the register of readers that tell the picture path an asset's canvas size and revision, and the `fingerprint` pixel art and vector art make their revision with), vectorart (#129: the canvas as a property, which ring is worth drawing, and the revision as a fingerprint of the drawing rather than a counter, a texture fill's picture included) + vectorPath (what a shape draws, as plain commands: closed rings fill, every ring strokes, a segment is a line while neither of its ends carries a handle; a paint resolved to sorted stops or the picture it names) + vectorPaint (#186: gradients and texture fills — where a paint lies when it is switched on, the colour between two stops, adding, moving and removing a stop, a paint moved with its shape, and the rule that a texture fill takes uploaded pictures only) + vectorBoolean (#187: union, subtract, intersect and exclude on the sampled outlines, each shape read by the even-odd rule; the result rings in the order Pixi's hole detection needs, every outline followed by its holes and preceded by the islands inside them) + vectorCurves (#208: every sampled point remembers its cubic and its `t`, so a run of result points along one cubic becomes that cubic again, cut with de Casteljau), pixelart (#130: the palette a picture is painted in, how the layers of a frame come together, the sheet of all frames, a frame id read as a cut of it, and the revision) + pixelCel (the file of one layer on one frame, and its SHA-256 name worked out in the browser) + pixelDraw (what the tools do to the indices: brush, line, rectangle, ellipse, fill, resize about an anchor, merge, a palette colour taken out) + pixelEdit (every edit of layers, frames and cels as a function from one state to the next), polygon (an outline checked, cut into convex pieces and clipped to a rectangle), tile (the three kinds and their block shapes, reading a tile's pictures, the animation step), autotile (which quarter tile a neighbourhood asks for, the 47/16 tiles a block produces, 1 for a plain tile), tilemap (the cells of a layer, which neighbours a cell is joined to, the cells a stroke or a rectangle covers), tilemapCollision (the solid cells of a map, drawn in or out by their tile's collision scale and merged into rectangles, one group per one-way angle and per surface (`tileMaterials`, #193), the outlined cells as polygons — an autotile's outlines cut into its quarters and pieced together per cell like its picture —, where one sits in the world, and which cells of a placed map a world rectangle can reach, in cells (`cellsWithin`, #184)), animation (which frame at time t, a row's value there, what a row may aim at, the players on an object; KeyRef and its lookups) + animationPreview (the root at a frame, written into copies), graphLookup (what a graph sees of the project: behaviors to run, state machines to read), Scope (how long a shared value lives: per instance, one for the run, or one per scene and rebuilt with every scene that loads, #164 — for a state machine's current state and for the values of a Variables asset), collisionLayers (which colliders may meet: the project's named layers, a collider's layer and mask, and the one rule `layersMeet` the engine, Solids and the event pair search all answer by)
+src/core/model/        Project (object holders), Asset + AssetTypes, SceneObject, Properties (value types), hierarchy, walk (generic parent/child walks), instance (container content resolved from its template), usages (where an asset is used), container (the cycle guard), placement (what may be dropped where), texture (frames, the slice grid, a frame's collision outlines), frameOutline (#193: a frame's outlines as a collider wears them, centred, a pixel to a unit, cut into pieces once per drawn list), traceCollision (#161: a frame's outlines read off its picture — the pixels from an alpha threshold on are solid, each 4-connected island is walked round along the pixel edges and cut down to a few corners without ever crossing itself; crumbs below 1 % of the frame drop out), generated (pictures that are drawn rather than uploaded, #185: the key `gen:<assetId>@<revision>`, the register of readers that tell the picture path an asset's canvas size and revision, and the `fingerprint` pixel art and vector art make their revision with), vectorart (#129: the canvas as a property, which ring is worth drawing, and the revision as a fingerprint of the drawing rather than a counter, a texture fill's picture included) + vectorPath (what a shape draws, as plain commands: closed rings fill, every ring strokes, a segment is a line while neither of its ends carries a handle; a paint resolved to sorted stops or the picture it names) + vectorPaint (#186: gradients and texture fills — where a paint lies when it is switched on, the colour between two stops, adding, moving and removing a stop, a paint moved with its shape, and the rule that a texture fill takes uploaded pictures only) + vectorBoolean (#187: union, subtract, intersect and exclude on the sampled outlines, each shape read by the even-odd rule; the result rings in the order Pixi's hole detection needs, every outline followed by its holes and preceded by the islands inside them) + vectorCurves (#208: every sampled point remembers its cubic and its `t`, so a run of result points along one cubic becomes that cubic again, cut with de Casteljau), pixelart (#130: the palette a picture is painted in, how the layers of a frame come together, the sheet of all frames, a frame id read as a cut of it, and the revision) + pixelCel (the file of one layer on one frame, and its SHA-256 name worked out in the browser) + pixelDraw (what the tools do to the indices: brush, line, rectangle, ellipse, fill, resize about an anchor, merge, a palette colour taken out) + pixelEdit (every edit of layers, frames and cels as a function from one state to the next), polygon (an outline checked, cut into convex pieces and clipped to a rectangle), tile (the three kinds and their block shapes, reading a tile's pictures, the animation step), autotile (which quarter tile a neighbourhood asks for, the 47/16 tiles a block produces, 1 for a plain tile), tilemap (the cells of a layer, which neighbours a cell is joined to, the cells a stroke or a rectangle covers), tilemapCollision (the solid cells of a map, drawn in or out by their tile's collision scale and merged into rectangles, one group per one-way angle and per surface (`tileMaterials`, #193), the outlined cells as polygons — an autotile's outlines cut into its quarters and pieced together per cell like its picture —, where one sits in the world, and which cells of a placed map a world rectangle can reach, in cells (`cellsWithin`, #184)), tilemapMemo (what a map's cells work out to, kept while they hold the same: a version per cell map compared cell by cell, since strokes paint in place), animation (which frame at time t, a row's value there, what a row may aim at, the players on an object; KeyRef and its lookups) + animationPreview (the root at a frame, written into copies), graphLookup (what a graph sees of the project: behaviors to run, state machines to read), Scope (how long a shared value lives: per instance, one for the run, or one per scene and rebuilt with every scene that loads, #164 — for a state machine's current state and for the values of a Variables asset), collisionLayers (which colliders may meet: the project's named layers, a collider's layer and mask, and the one rule `layersMeet` the engine, Solids and the event pair search all answer by)
 src/core/properties/   PropertySchema, kinds (one row per value kind), listItems (an item's kind, read off its value), resolve (the only override merge), deviation (what is gold), collider/camera/bounds geometry (with the side a one-way collider blocks from, and the rectangle around a shape a broad phase looks at first, #184), convex (capsules and polygons: rounded convex pieces against each other), ray (where a ray meets a shape, in double precision), rigidbody (what the engine reads off a rigidbody, a collider's material and the scene), aspect, enabled, editorRun, assetRef/textureRef (how a reference reads), declaredRows (the row a Property node declares in a shader or particle graph, and the params that node has in both)
 src/core/util/         list (take out, put back and move an item — what a command's undo is made of), vec (dot, the closest point on a segment — shared by the collider maths, the outline hit area and the polygon grips), color (`mixColor`, channel by channel — keys of an animation, stops of a gradient, the particles' Mix colour)
 src/core/commands/     undoable commands (pixelArtCommands: one command runs any pixel art edit and keeps the state before it, #130), CommandStack, SetBagValueCommand base, RenameCommand base (undone by renaming back: variable, struct field, port), MoveCommand base (undone by moving back: tile picture, tilemap layer, vector shape), vectorArtCommands (#129: the shapes of a drawing, one gesture one command), one import command shape for texture/font/sound, require.ts (validated lookups, and what an instance may not change), naming.ts

Tilemaps.md

@@ -314,6 +314,25 @@ worked out in world units at all. Measured on a map of 20 × 20 outlined cells o
 one `Move` cost 148 ms before and 0.26 ms after; with 8 corners, 34 ms and 0.27 ms. Nothing about
 the result changes — what is left out could not have been met.
 
+What the cells work out to is **remembered while they stay the same**
+(`core/model/tilemapMemo.ts`). The scene view, the game view, the collision system and the physics
+all ask for a map's tiles and solids every frame, and an animated tile makes the views draw every
+frame. Before, each of them cut every outline into its quarters and pieced every cell together
+again, so a map that only stood there cost a frame. Now:
+
+- The tiles of a layer, the blocking cells, their rectangles and polygons are kept per content.
+  The content is compared cell by cell, not by object, because a stroke paints the cells in place.
+  A painted cell, a tile switched off Solid, a new outline or a new tile kind is seen at once.
+- A tile's cut outline is kept per outline list. The model replaces the list instead of editing
+  it, so the list stands for its corners.
+- The same cells hand out the very same rectangles and polygons. The physics tells by that, and by
+  the map's place and settings, that it need not work the map's pieces out again every tick.
+
+Measured on a map of 39 × 18, 8 × 8 and 43 × 20 cells on three layers, with an animated water
+tile and an outlined hill tile (5 outlines), script time per frame on the main thread went from
+17.7 to 5.8 ms with nothing selected, from 26.2 to 8.6 ms with the map selected and from 29.9 to
+8.7 ms in Play. That is 52, 38 and 33 fps before and 60 fps in all three after.
+
 A frame still costs what it touches: an object standing **inside** many outlined cells is tested
 against each of them, so an outline of a hundred corners around every cell of a lake is dearer than
 a few around its shore. Draw as few corners as the shape needs.