The G3d-Viewer did not show some models from newer tilesets ( birch-forest/ volcanic island ...). This happened because opacity is somehowignored ingame for tileset objects, but in g3d-viewer ist used. This resulted in a full transparent rendering in the g3d viewer.
In the code I now set the opacity to 1 if its 0 , but in general i think those models are buggy :-/ . But I want to see transparency textures in blender too and i only know a way when I set the material to transparent.