Cloudshadow — weather that throws a real shadow, for RPG Maker MZ

Weather your map already knows it should have.

Cloudshadow builds the sky above your map and draws the shadow it casts on the ground below. Not a tinted overlay and not a looping cloud PNG sliding across the screen: cloud masses with their own shape and altitude, drifting at three different speeds, whose shadow lands differently on water, roof, wall and grass because every tile carries how much light it loses and how high it stands.

The sky is derived, not typed

You do not author weather. Cloudshadow reads the map it is already on, the tileset kind, the region ids, how much open water there is, how built up it is, and the screen tone a day/night plugin has left behind, and picks one of five skies from that. Drop it in and every map in your project already has weather.

When you want to direct a scene, you override it:

• <cloudshadow: storm> in the map note
• region ids 61 to 65 for clear, fair, scattered, overcast and storm
• a variable, for weather that changes while the player watches

Interior maps opt out on their own.

The shadow lands by surface, and you can see it

This is the part a screen tint cannot do. A roof two tiles up meets the cloud before the grass beside it does, so the shadow edge on the tiles does not line up with the shadow edge on the ground. Still water shows you whatever is above it, so it is the surface a cloud changes most and the only one whose remaining light goes properly cold.

Measured on one frame of the gallery, under a storm sky: the open water loses 59.4% of its light at the deepest point, the roof 57.8%, the grass beside it 52.9%, a wall side only 33.2%. Those are not intentions, they are readings taken off the shipped screenshot.

And the shade has a ceiling. A cloud removes the sun, not the light, so a Cloudshadow shadow never reaches black, however heavy the storm.

It costs a shader pass, not a redraw

The cloud field is baked once per sky into a small tiling sheet and scrolled; the surface data is baked once per map. A frame of play writes about fifteen floats and draws nothing new. A storm at three altitudes costs what a clear sky costs.

• 10 draw calls per frame, 0 texture uploads, 0 bitmap dirties
• 0 display-object growth, the per-frame path allocates nothing
• 0 pixels read back from the GPU while you play
• 0 of 600 frames over the 16.67 ms frame budget, on three separate runs

A working demo map ships with it

The package contains a complete demo, a painted parallax with its map and tileset records, so you can see the effect on real ground the moment you install it and take it apart to see how the surface classification works. The landscape in every screenshot here is that demo, and it is ours: there is no stock RPG Maker art in any image on this page.

What is in the box

Two plugin files of raw, readable JavaScript. No minification, no bundler, no build step. Six parameters, five skies, a map-note and region-id interface, and a save that resumes the weather exactly where you left it.

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⚠️ Compatibility — the question you actually have

Tested against RPG Maker MZ with the stock scripts unmodified, verified by running the plugin in the real engine rather than only in tests.

Plugin Manager order:

1. CloudshadowCore.js — the sky field and the shadow it throws
2. Cloudshadow.js — the MZ binding

Core methods extended — 5 by saved-original prototype extension, none replaced: Game_System.prototype.initialize, Game_System.prototype.onAfterLoad, Spriteset_Map.prototype.createLowerLayer, Spriteset_Map.prototype.update, Spriteset_Map.prototype.destroy.

Because nothing is clobbered, Cloudshadow co-exists with other plugins that patch the same seams, including large suites. It appends its filter to the map's existing filter chain rather than taking the chain over, so the overlay and fog plugins you already run keep working. That is verified in a blank project, in the worst-case alphabetical plugin order a buyer actually gets when they drag both files in.