ORM Texture
Occlusion / Roughness / Metalness packed into one map
Also known as: ORM · Packed PBR map · RMA
Definition
An ORM texture packs three grayscale PBR maps — ambient Occlusion, Roughness, and Metalness — into the R, G, and B channels of a single image. This cuts texture samples and memory by two-thirds compared to using three separate maps. ORM is the de facto standard for Unreal Engine PBR exports; Unity URP/HDRP uses a similar packing called MaskMap (with different channel order).
In production
Substance Painter's default Unreal Engine 4 export preset packs Occlusion into R, Roughness into G, and Metallic into B automatically, which is why most marketplace assets and Quixel Megascans surfaces ship with an "_ORM" suffix rather than three separate PNGs. Unity's HDRP/URP MaskMap reorders the channels — Metallic in R, Occlusion in G, Detail Mask in B, Smoothness in A — so a texture packed for Unreal will render incorrectly in Unity until the channels are remapped, a frequent gotcha when porting asset packs between engines. Because ORM packs three grayscale maps instead of three RGB maps, memory drops from roughly 3x a same-resolution RGB texture to about 1x, which matters directly for mobile and VR texture budgets. Some engines also reserve the alpha channel for a fourth mask (detail or subsurface), so artists need to check the target pipeline's channel spec before baking rather than assuming the standard RGB order.
