v0.93.1 Clear Skies

A patch for a bug that has been in the sky for a long time: while you look around, a wedge of the sky would flash a flat colour for a single frame — a straight-edged slice, usually at a corner or side of the screen, cut off exactly at the horizon. It happened far more often while the camera was moving than while it was still, and it was over before a screenshot could catch it.

What it was

The renderer built each pixel's ray as the line from the near plane to the far plane. With a far plane hundreds of thousands of units out, the far point sits at the very edge of 32-bit floating-point precision — and for some camera poses, the rounding tipped over along a straight line across the screen. Beyond that line the direction came out as not-a-number, and a sky shader given no direction painted its bare horizon colour. Every camera pose had its own line, or none; looking around visited many poses a second.

The ray now runs from the near plane to a point halfway down the depth range. It is the same line, without the precision cliff at the end of it. On a test rig that swung the camera around a project continuously, the flash appeared 156 times in eleven thousand frames before and not once in ten thousand after.

Also in this patch

floptle shot never compiled a project's Sky shader, so every picture of a scene with a procedural sky showed the flat Skybox colour instead. It draws the sky now. The shot verb also takes --frames N and --turn DEGREES to photograph a sequence while the camera sweeps, and FLOPTLE_FRAME_DUMP=<dir> writes every frame the editor or a build presents to that directory — the tools that caught this bug. See docs/export-builds.md.

Upgrading

Nothing to change.