The composite stages render at the target

trails and kaleido_* used to run at a fixed 1280x720 internal grid and present stretched, which on any display above 720p upscaled the whole frame — including line art that had just been rasterized at full resolution. That is why a preset could look sharp with the stages off and “upsized from something smaller” with them on, and why the shipped line presets were written without trails.

Both stages now size their grid from the render target (quantized to a 256 px step, capped), so composing a look no longer costs sharpness and the line presets can take their feedback back. Nothing to bind — it follows the window.

Two consequences worth knowing:

• A resize clears the trail. Crossing a quantization step reallocates the accumulation, so the afterglow restarts. Rare rather than continuous, but a slow window drag will blink it.
• The cap is a real ceiling. Above it the grid stops growing and both axes scale by one factor, so a very large or very wide window resolves the stages slightly softer than native rather than unboundedly expensively.

Composing a stage never changes the picture’s proportions, at any window size. The grid’s own shape is not the picture’s: it is quantized, so it is only roughly your window’s ratio, and the scene is drawn at the window’s aspect and then stretched back by exactly the inverse when the stage presents. The two cancel, so a circle is a circle with trails on and with it off (ADR-0037).

A scene that took its aspect from the grid instead would stretch the whole frame by up to 28 % on common window sizes (1280x800 and 1366x768 among them) the moment a stage was composed. A preset comment that talks about a stage changing the shape of a figure is stale.