DrftPart

interface DrftPart

import type { DrftPart } from '@driftengine/assets';

Properties

Name	Type	Description
`mesh`readonly	`MeshHandle`
`albedo`readonly	`number`	Which of the asset's images this surface wears, or -1 for none.
`orm`readonly	`number`	Which image carries its occlusion, roughness and metallic, or -1 for none.
`normal`readonly	`number`	Which image carries its surface-space normals, or -1 for none. More Carried by the container since `MATL` reached stride 72 and dropped here until 2026-08-23, which is the whole of why a bought model looked smoother than the one its maker shipped: the baker wrote the index, the reader read it, the renderer has taken a normal map through `SurfaceMaterial.normal` since normal maps landed, and this was the one step that did not pass it on. Panel seams, stitching, tread and every other detail an exporter bakes into a normal map rather than into geometry was arriving and going nowhere.
`emissive`readonly	`number`	Which image carries its emission, or -1 for none. More The fourth and last index `MATL` carries, passed on from 2026-08-24. It was written by the baker, read by the reader and dropped here for the same stretch the normal map was — but for a stated reason rather than by oversight: no renderer took an emissive map until now, so there was nowhere to pass it. `SurfaceMaterial.emissive` is that somewhere.
`roughnessScale`readonly	`number`	glTF's three factors, in the shape `SurfaceMaterial` takes them. More Carried on the part rather than looked up from the material, because a caller building a `setMaterial` call has the part and not the index that produced it.
`metallicScale`readonly	`number`
`occlusionStrength`readonly	`number`
`opacity`readonly	`number`
`reflectivity`readonly	`number`
`cutout`readonly	`number`	Alpha below which this surface's fragments are discarded, 0 for one that discards nothing. More The pair to `opacity` and not a weaker version of it: a cutout decides which texels of the surface exist, an opacity decides how much light passes through the ones that do. It is what `SurfaceMaterial.cutout` takes, and until `MATL` grew the field there was no way for a source format to say it — a masked grille arrived as a solid rectangle, and a vehicle format's alpha test was being spent on the opacity, which drew nine surfaces of a hundred and two as nothing at all.
`blend`readonly	`boolean`	Whether the part blends: its texture's alpha is coverage, so it is drawn translucent whatever its `opacity` says. glTF's `BLEND` with a factor of 1 is the case: a leaf's shape is in its alpha.
`doubleSided`readonly	`boolean`	Whether both faces are seen: glTF's `doubleSided`. Drawn without culling, each face lit as the front.
`glass`readonly	`GlassOptions \| null`	The glass this part is, from its file or from `DrftLoaderOptions.surface`, or null for a part that lets no light through. A glass part is also `blend`, so a caller drawing blended parts translucent passes this as the draw's `glass` and every pane arrives as the file or the override said. One object per merged group, shared by its parts, so it is not rebuilt per draw.
`instances`readonly	`DrftPartInstances \| null`	The copies this part is drawn as, or null for a part drawn once. More A mesh the file places many times (`INST`, 1.18) is uploaded once and drawn through the engine's instanced path: `drawInstanced(batch, data)`, and `sink.instanced` for a shadow. The placements are uploaded when the part is made and carry the fit, so a caller passes them as they are. Null for every part of a file with no instances, which is every file before 1.18.
`reveal`	`number`	0 to 1 as this part arrives, for a caller that would rather it faded in than appeared. More Advanced by `update`, so it follows the frame's own clock and holds when the frame holds. A caller that wants parts to pop in can ignore it; one that wants a build fades on it.