Проверь так, должно работать.
; EntityAlpha Example
; -------------------
Graphics3D 640,480 ,32,2
SetBuffer BackBuffer()
camera=CreateCamera()
light=CreateLight()
RotateEntity light,90,0,0
cube=CreateCube()
Back=CreateCube()
PositionEntity cube,0,0,5
PositionEntity back,0,0,15
ScaleEntity Back,10,2,1
EntityColor back,255,0,0
; Set initial entity color values
Alpha#=1
While Not KeyDown( 1 )
; Change alpha value depending on key pressed
If alpha#<0.01 Then alpha# = 0
If alpha#>1 Then alpha# = 1
If KeyDown( 2 )=True And Alpha#>0 Then Alpha#=Alpha#-0.01
If KeyDown( 3 )=True And alpha#<1 Then Alpha#=Alpha#+0.01
; Set entity alpha value
EntityAlpha cube,Alpha#
TurnEntity cube,0.1,0.1,0.1
TurnEntity back,1,0,0
RenderWorld
Text 0,0,"Press keys 1-2 to change EntityAlpha"
Text 0,20,"Entity Alpha: "+Alpha
Flip
Wend
End