3ds Max - export material custom attributes

I want to control roughnessfactor and metallicfactor in the exported gltf directly from 3ds Max. I am looking at custom attributes connected to a Physical Material in 3Ds Max but can´t really take control over the parameters as both metallicfactor and roughnessfactor are always exported as 1. Any ideas about how to do that?

pinging @Guillaume_Pelletier

There is a known bug with the Rollover control on Max… i will have a look if this is something we could bypass


had a look and the value are well exported using Max2020.

exported as

	"materials": [{
		"pbrMetallicRoughness": {
			"baseColorTexture": {
				"index": 0,
				"extensions": {
					"KHR_texture_transform": {
						"offset": [0.0, 0.0],
						"scale": [1.0, 1.0],
						"texCoord": 0
			"metallicFactor": 0.3,
			"roughnessFactor": 0.5
		"alphaMode": "BLEND",
		"name": "Building"

You might take attention of that 3DSMAx override these “basic” values when a map is set.