GLTF Exporter forces all materials with texID == 0 to opaque black

[Dnawrkshp]

Is this intentional? When exporting armor files to gltf the first texture is id 0 and is rendering as black. Not sure if this behavior is required for non-armor files.

Happy to submit a PR changing texID == 0 to texID < 0 or whatever is desired.

Replanetizer/LibReplanetizer/Serializers/Exporters/GLTFExporter.cs

Lines 374 to 384 in d9bb7cc

	public GLTFMaterialPBRValues(int baseColorTextureIndex, int texID)
	{
	if (texID == 0)
	{
	this.baseColorFactor = new float[] { 0.0f, 0.0f, 0.0f, 1.0f };
	}
	else
	{
	this.baseColorTexture = new GLTFMaterialPBRValuesBaseColorTexture(baseColorTextureIndex);
	}
	}

Replanetizer/LibReplanetizer/Serializers/Exporters/GLTFExporter.cs

Lines 400 to 405 in d9bb7cc

	public GLTFMaterialEntry(TextureConfig conf, int texOffset)
	{
	this.name = "Material_" + texOffset + "_" + conf.id;
	this.alphaMode = (conf.IgnoresTransparency() || conf.id == 0) ? GLTFMaterialEntry.OPAQUE : GLTFMaterialEntry.MASK;
	this.pbrMetallicRoughness = new GLTFMaterialEntry.GLTFMaterialPBRValues(texOffset, conf.id);
	}

[MilchRatchet]

I don't completely remember why this check was necessary. My best guess is that back in the days we clamped the negative texture IDs to 0, at least I remember objects like the broken ship on Tabora rendering with texture 0 in older versions of Replanetizer.

So I think changing this to texID < 0 should be correct.