Channel Packer (ORMA)

Standard ORM packing crams three maps into RGB. ORMA adds a fourth - the alpha channel - so a single RGBA texture carries occlusion, roughness, metallic, and a transparency/mask map. That's the whole trick: four maps, one texture, no extra draw calls. It's aimed squarely at masked materials - foliage, chain-link fences, decals, anything where you need a cutout alpha alongside your ORM.

The use case is specific but common enough that the pack spun it into its own node rather than overloading the plain RGB packer. Vegetation is the textbook example: you get the leaf material's AO/roughness/metal in RGB and the leaf shape in alpha, all in one file.

How it works

It takes occlusion, roughness, and metallic as grayscale sources and writes them to R, G, and B respectively. The optional alpha input goes to the A channel. If you don't connect an alpha, it defaults to fully opaque (a solid white channel) - which is a genuinely useful default, because it means the node is a drop-in ORM packer when you don't have a mask, and an ORMA packer when you do. Each input gets luminance-converted if needed and auto-resized to match the first input, same as the rest of the pack's channel tools.

The inputs

• occlusion - AO map → R.
• roughness - → G.
• metallic - → B.
• alpha (optional) - transparency/mask → A. Defaults to white/opaque if unconnected.

Output: orma_packed - a single RGBA IMAGE.

Where it fits and the trade-off

Ordering matters and it's the easy thing to get wrong: this is O-R-M-A (AO, roughness, metallic, alpha). The pack also ships a plain RMA packer with a different channel order (roughness, metallic, AO), and if you mix up which packer you're using, the maps silently land in the wrong slots - the texture loads fine and just looks wrong, which is the worst kind of bug. Note which convention your engine expects before you commit. Also remember RGBA only helps if the tooling keeps the alpha: PNG and EXR preserve it, but a JPG will silently drop your transparency.

Installation

Part of amtarr/ComfyUI-TextureAlchemy, under Add Node → Texture Alchemist → Channel. Install via ComfyUI Manager (search "TextureAlchemy") or:

cd ComfyUI/custom_nodes
git clone https://github.com/amtarr/ComfyUI-TextureAlchemy

Restart ComfyUI. No dependencies, no models - pure channel concatenation.