Interface ReadPixelsOpts<K>

Source render target. Typed as the base RenderTarget so a cube target from either backend (WebGLCubeRenderTarget, or three/webgpu's CubeRenderTarget, which is NOT a WebGLRenderTarget) is accepted; see faceIndex.

Pixel-format discriminator. Determines the returned typed-array kind.

Cube face to read when target is a cube render target (0..5 in three's px, nx, py, ny, pz, nz order). Threaded into WebGL's activeCubeFaceIndex argument and WebGPU's faceIndex argument — the two signatures put it in different slots (after the destination buffer vs after textureIndex). Ignored for a 2D target.

X offset in pixels (top-down convention). Defaults to 0. Full-target reads (the common case) leave this at 0; sub-region readers (e.g. the picking 5×5 voter) supply canvas-space top-down coords and the primitive converts to the backend's framebuffer convention internally.

Y offset in pixels (canonical top-down, row 0 = top of source). The primitive flips this to the bottom-up framebuffer convention internally when caps.framebufferYDown === false. Defaults to 0.

Region width in pixels. Defaults to target.width.

Region height in pixels. Defaults to target.height.

Default false. The primitive's canonical return convention is rows in top-down order (row 0 = top of the source target). Pass true to receive bottom-up rows instead — used by callers whose downstream consumers expect scene-space row order (e.g. EXR export).

Optional pre-allocated destination buffer for the raw readback. Must be exactly width * height * 4 elements of the right typed-array kind for kind. When provided, no fresh allocation is made for the raw readback; ideal for hot paths (e.g. picking) that fire at mouse-event rates.

Optional pre-allocated destination buffer for the row-flipped output (only consulted when flipY is the default false). Must be the same size and kind as out, and a different buffer than out (the row-flip interleaves reads/writes across rows and cannot operate in place). When provided, the row-flip writes into this buffer instead of allocating one. The returned pixels is this buffer (not the raw out).