sgdk-isometric

SGDK isometric

Keep the map, movement surfaces and drawing separate. Isometric projection makes a 2-D world with height look three-dimensional; it does not supply physics, resource streaming or automatic depth sorting in SGDK.

Establish the coordinate contract

Choose tile width/height, map units, vertical scale, foot anchors and rounding. Use world coordinates for collision and surfaces, then project and subtract the camera for display. Keep the camera out of draw-order comparisons. Read coordinates and elevation for formulas, known-height inverse projection, stairs, underpasses and controller mapping.

A character's elevation is not its drawing depth. Sorting by screen Y or x + y - z alone fails when one character walks above a bridge and another walks beneath it. Use a simple foot-depth key only when the content's assumptions make it sufficient. Read depth and occlusion before choosing a sorter or splitting scenery.

Design art that can be sorted

• Give each asset a consistent foot anchor and a collision footprint independent

of its visible pixels. Trim transparency only if the anchor is preserved.

• Keep flat ground in a background when practical. Keep overhangs, foreground

pillars, bridge decks and other independently occluding pieces separable.

• ResComp cutting a large sprite into hardware pieces does not let a character

sort between those pieces; split into logical objects where needed.

• For complex overlap, use bounded ordering constraints with stable IDs and

explicit support rules. Surface ownership can resolve a stair proxy overlapping the actor standing on it. Do not use an arbitrary tie rule to hide intersecting objects or cyclic content.

• Treat a cutaway or silhouette as a presentation choice. Hiding a roof must not

silently remove its collision or change the character's surface.

Integrate and budget

Pull ewrogers/sgdk:latest and verify the selected SDK's rendering APIs. Read SGDK rendering and budgets for actual depth semantics, plane priority, palette ownership, hardware pieces and retained DMA. Cache immutable scenery relationships if pairwise work is significant; rebuild when that scenery changes. Keep dynamic work, capacity failures and graph cycles visible and bounded. Measure a release build rather than assuming fewer objects means a cheap frame.

Test projection signs and negative rounding, height round trips, above/below ordering, disjoint projected shapes, stable ties, cycle/failure results and walkway boundaries. Compare a cached sorter against the complete one. Verify compiled assets and target arithmetic, then test actual movement and visuals. PAL/NTSC build and logical tests do not certify VDP timing or console performance.

Isometric Lab: Lantern Aqueduct demonstrates a small original garden, stepped approaches, a bridge and an underpass. Its art, palette, music and movement tuning are illustrative, not requirements for a game.