MiniMax H3 Resolution Selector (best-effort)

MiniMax H3 has its own ideas about canvas math: a 768px short edge, a 768×1344 pixel-area cap, 32-multiple rounding, and a frame grid you have to land on or the generation fails. You could hand-type width and height into a latent node every time, or you could use this node and pick a canvas by name.

It outputs the four numbers an H3 generation actually needs - width, height, size (as a "W×H" string), and length (frame count) - from a resolution preset, with two overrides.

The controls:

• resolution - a combo of ~46 "W×H" presets spanning nine named aspect ratios (1:1, 16:9, 9:16, 4:3, 3:4, 3:2, 2:3, 21:9, 9:21) across five size tiers, from 384px up to 1152px. This is the widget that's actually parsed. It's the source of truth for width/height.
• aspect_ratio - exists as a human-readable label next to the resolution string. The original private node probably kept the two in sync with JavaScript; a plain Python node can't, so here the ratio is just a label and the resolution string wins. Set the resolution and ignore it.
• duration (seconds, default 5) and fps (default 24) - converted to a frame count and snapped to H3's frame grid (17k + 5 frames) using the same align_frame_count math as ComfyUI's real native nodes, so length comes out valid.
• custom_width / custom_height - set both above 0 (they're step-32 integers) and they override the preset entirely.
• reference_image - if wired, its exact width:height ratio overrides the aspect_ratio/resolution preset (but not the custom override). The node steps through 32-aligned sizes at that exact ratio and picks the largest that still fits the selected preset's pixel budget. Handy when you're generating from a reference and want the canvas to match it.

Outputs: width, height, size (STRING), length (INT). Wire width/height into your latent node and length into anything that wants a frame count.

Honest provenance, because it matters with this pack: this is a best-effort reimplementation of a node type from a privately-distributed H3 workflow with no public source. The preset math is copied verbatim from ComfyUI's own native MiniMax H3 node code (so length stays byte-for-byte compatible), and two pieces - the duration→frame-count snapping and the exact-ratio reference sizing - are adapted with credit from the separate, real ComfyUI-ResolutionSelector pack's ImageRatioSelectorZerohackz node. Two legacy "384×576"/"736×1120" values are kept in the list so older saved workflows still load.

Install, plus the H3 ecosystem you need around it:

cd ComfyUI/custom_nodes
git clone https://github.com/jjmaden/comfyui-jjmaden-random-nodes

Restart ComfyUI, or search "JJMaden Random Nodes" in ComfyUI Manager. You need a ComfyUI build with native H3 support (it's in current ComfyUI - H3 got day-zero support). The pack itself is MIT with zero Python dependencies; the H3 weights are a separate, large download.

The thing to internalize: aspect_ratio looks like a control but isn't one - if you change the ratio label and the resolution doesn't change, that's expected, not broken. And the reference_image override is a nice-to-have that turns "match this image's proportions" into a one-wire operation. For the everyday "I want 1344×768 at 24fps" job, it's a clean shortcut that keeps your canvas numbers valid without you doing the mental arithmetic.