"In the past , I accidentally solve this once by modifying the model's distance from the ground randomly , but now it seems it's won't have any effect anymore " , so by that you mean in the past 30 days ? Why do u think anyone should bother trying to help u with an issue of an outdated trial version when u just stated u have intention of buying the engine , whichmeans u cant actually make a game(u cant publish with the demo) , which means helping you resolve this issue would be a waste of time because in 30 days you wont even be able to use gamestudio anymore. Now , the demo in the downloads is the demo of 6.31 , not 6.22 , and if this is an old demo u've been using it would have already expired a ton of time ago because 6.22 demo is OLD. Now to be honest , it sounds like ur making ur game with the warez version of gamestudio , the notorious 6.22 version , which seems to be the version you have , and arent willing to update , maybe because there is no 6.31 warez version right , LOL. And lets say u did have a legit demo , a demo is only for trying something before u buy , not for making a game with it , or exploring every nuke and cranny of the engine , but i'm thinking ur a warez user. The lite version of gamestudio is only $49 , how is that too expensive ? Thats insane , games are that expensive , how is a game development suite for that price too expensive ? Someone report this thread to Conitec so they can take appro[riate action.