Reference images

Line a reference image up with your world, mark it up and compare two versions.

What it’s for

This area lets your assistant work against a reference image in world coordinates. It can cut the image into a tile grid that is tied to positions in your level, draw marks onto it at world positions, and put two images side by side with a difference image. Every position is in world centimeters, so nobody has to convert pixels by hand.

Use it when your assistant is placing things against a plan, a blockout, or a screenshot of how the level should look. The loop is simple: estimate a world position, draw it back onto the reference, look at it, correct it. Reading positions off a whole-map image at once is where errors come from. Cutting it into full-resolution tiles makes the estimates far more accurate.

Everything here is plain cropping, drawing and blending, and every step writes a file you can open. Nothing makes a judgment for you. A comparison reports how many pixels differ and by how much, and you decide what that means. A mark only counts as drawn when the pixels under it actually changed. Anything that cannot be represented exactly is refused instead of rounded.

Things you can ask

Cut a reference map into tiles

Each tile records the exact patch of ground it covers. A tile of the reference and the same tile of a capture always cover the same ground, at any resolution.

You: Cut the level reference map into a 4x2 grid over the playable area.

Cut level_plan.png into eight tiles at 4.88 cm per pixel. Each tile knows which part of the level it covers.

Mark a world position on the reference and check it

You give world positions, not pixels. If a point falls outside the tile, you are told so instead of the mark being pushed to the edge.

You: Mark where you are about to put the radio tower, with a 500 cm grid.

Marked the tower at pixel (614, 727) on the tile, with a 500 cm grid. Open the annotated PNG and tell me if that is the spot.

Compare a capture against the reference

If the two images cover different ground or have different resolutions, the comparison is refused and you are told which one, because each has a different fix.

You: How close is the blockout to the plan?

11% of pixels differ, and brightness matches, so this is not an exposure difference. The difference image
shows the changes along the north wall.