Your code, corrected: (use this instead of your old code)
;Name of application AppTitle "My First Terrain And First animated Character" ;Initialise Graphics mode Graphics3D 800,600,16,1 SetBuffer BackBuffer() ;Camera has to be set, so the scene is visible Camera=CreateCamera() PositionEntity camera,30,1,2,True ;Light The Scene, so that it doesn't look flat Light=CreateLight() RotateEntity Light,90,0,0 ;Create the "Terrain" Entity... terrain=LoadMesh("terrain1.x") PositionEntity terrain,0,0,5 RotateEntity terrain,0,20,0 TranslateEntity terrain,30,0,-.15 ;...and texture it Grass=LoadTexture("grass2.bmp") EntityTexture terrain,Grass ;Create the "Box" entity and animate it box=LoadAnimMesh("model\BOX.B3D") ScaleEntity box,.1,.1,.1 PositionEntity box,0,0,5 TranslateEntity box,30,0,-.15 SetAnimKey box,15,True,True,True AddAnimSeq(box,15) Animate box,1,2,0,100 ;Set Collision types fot the "collisions" command 1-player, 2-ground type_box=1 type_terrain=2 EntityType box,type_box EntityType terrain,type_terrain ;Adjust Radius of Sphere, that's used for Sphere-Polygon collisions box_radius#=1 EntityRadius box, box_radius ;Initialise Collisions between player and ground Collisions type_box,type_terrain,2,2 ;Dither scene, so that it does look good with 16 Bit Color-Depth Dither True ;Main Loop While Not KeyHit(88) ;press F12 To Exit ;Press F11 to see the world in Wireframe mode If KeyHit(87)=True Then enable=1-enable WireFrame enable ;Parent the player to the camera, so that moving the player makes the camera follow it EntityParent(camera,box,1) ;Keyboard input (cursor-keys) for moving the player around If KeyDown( 32 )=True Then TurnEntity box,0,-1,0 If KeyDown( 30 )=True Then TurnEntity box,0,1,0 If KeyDown( 31 )=True Then MoveEntity box,0,0,-0.05 If KeyDown( 17 )=True Then MoveEntity box,0,0,0.05 ;Update the animation-Frames and Render the calculated scene, Flip Back- with Frontbuffer after that, so the new frame becomes visible UpdateWorld RenderWorld Flip Wend ;Free the Memory and end the program ClearWorld End