Projections take their depth range as a required argument

Decided

D-0086, settled by the language’s author: part of spec §18.

Mat4::perspective and Mat4::orthographic take a DepthRange, .MinusOneToOne or .ZeroToOne, as their last argument, with no default. Chosen by the user on 2026-10-23.

Mat4’s memory layout suits every graphics API Dazzle is likely to draw with: OpenGL, Vulkan, Direct3D, Metal and SDL3’s GPU API all read it as it is (raylib’s Matrix is the exception, as a type of its own, T-0046). What differs between them is where a projection puts depth. OpenGL maps near..far onto -1..1; the rest map it onto 0..1. Until r77 std had only OpenGL’s, and the wrong one does not fail: it clips geometry near the camera and wastes depth precision.

• Both, chosen at the call (chosen). The choice is visible where the matrix is built, and a program that picks its API at run time passes a variable.
• No default. Defaulting to OpenGL’s range would let a Vulkan program skip the argument and draw wrongly with nothing to say why.
• Chosen per project, by import or by dazzle.toml (rejected). The user’s first idea. It would make one call, Mat4::perspective(…), return different matrices in different projects, decided by a setting nowhere near it, which D-0057 rules out for names. It is glm’s GLM_FORCE_DEPTH_ZERO_TO_ONE, a known trap when a library and a game are built with different settings, and it cannot serve an engine that chooses its API at run time. A program that does want one choice for its whole build gets it from its own code: a const of type DepthRange, or one picked by #if on a flag it registers (§12.10).
• Separate names, perspective_zero_to_one (rejected): the choice can be skipped by calling the shorter name, and a run-time choice needs an if at every call.

Clip-space y is left alone: it points up everywhere but Vulkan, where the usual fix is a viewport of negative height, not a different matrix.

Spec: §14.4.