I haven't tried via Sktechup, only with 3DSMax and here's how it worked.
Example for a patch of grass.
1) in 3DSMax, rename each sub-object with the __nocollision__noshadow suffix =>
In my example, Grass_Short_Medium is 1 single plane of grass like yours.
In a scenery I would repeat it at several places :
Grass_Short_Medium__nocollision__noshadow_001
Grass_Short_Medium__nocollision__noshadow_002
Grass_Short_Medium__nocollision__noshadow_003
...
2) still in 3DSMax, group them all as a single object (in my example yverdon_Grass_obj), no more need for the __nocollision__noshadow suffix :
With several patches of grass the group would look like that:
yverdon_Grass_obj
-> Grass_Short_Medium__nocollision__noshadow_001
-> Grass_Short_Medium__nocollision__noshadow_002
-> Grass_Short_Medium__nocollision__noshadow_003
...
3) select yverdon_Grass_obj and proceed with export selected to export in your work folder as yverdon_grass.tgi
4) edit the conversion tsc file to reflect this and lauch the converter
<[tmsimulator_scenery_object][element][0]
<[string8][type][object]>
<[string8][geometry][yverdon_grass]>
<[vector3_float64][position][6.616438 46.764901 0]>
<[float64][orientation][0]>
<[int32][autoheight_override][-1]>
>
5) launch the converter and test in AFS2
That's the way I think I did it, but it's a very long time ago.
As far as I remember, the object_transparent_atc type if for using a different shader so that grass looks more uniform.
I think the __nocollision or __ noshadow tags must be given before exporting to TGI
As you can see, there was no more mention of these tags in the TGI and texture files, and thus no mention either in the resulting TMB file, so it apparently has to do with how the TGI is being generated.
There, I'm not sure the TGI exporter of MCX can handle it...
In case you have AC3D, you may try the same as in 3DSMax.
Cheers
Antoine
Cheers
Antoine