3D turrets

Ive created a few variations on this..but there are always
problems..taking advantage of the hierarchy system within
blitz makes things much...but there are many problems..
Sure if you fix your turret so that it is basically 2d, its
Y axis being equal to World Y...but as soon as you allow
full 360 orientation..rotations invert..yadda..
Another problem is the Arc-Lim idea..limiting the amount
by which a turret a rotate...

Ive mad cludgey versions in the past..but i was wondering
if someone had any elegant versions?

Anyway..im of to play with some crossproduct ideas....

cheers! ;)
Matt....

Use this function:

Function AngleDifference#(angle1#,angle2#) 
; Finds the difference between two angles fron -180 to 180
;
; Returns the difference.
Return ((angle2 - angle1) Mod 360 + 540) Mod 360 - 180 
End Function

Then you can find out where it's pointing by using

angle# = angledifference(entityyaw(gun),30) ; where 30 is the direction you want it to be pointing at rest.

This will return -180 to 180 reletive to the resting direction.

You can deal with everything else nice and easily from there.

You'll need to be a bit more specific about the problems you're having.

Using Blitz3D's parent-child entity relationships should allow you to set up turrets effectively.

As far as limiting the degree of arc, just check to see if the entity has exceeded the maximum degree of arc and move it back to the maximum rotation allowed. You will possibly need to store the rotation value in variables, which are updated by the amount of rotation added or subtracted, as some of Blitz's functions to return the current rotation return fairly useless values.

Here's some code I use to set up a user entity with a camera parented to it, which is designed to work in a similar fashion to a turret.

; -- Create user entity and user's camera.
Global user = CreatePivot()
Global user_camera = CreateCamera( user )
;^^^^^^

This code allows the above entity to 'mouselook', with the pitch rotation of the camera limited to 180 degrees. (Note: Variables that start with 'the_' are locals.)

Function mouselook()

	If ( MouseX() > mouse_right_limit ) Or ( MouseX() < mouse_left_limit ) Or ( MouseY() > mouse_bottom_limit ) Or ( MouseY() < mouse_top_limit )
		MoveMouse viewport_center_x, viewport_center_y
		current_mouse_x = viewport_center_x
		current_mouse_y = viewport_center_y
	EndIf

	the_new_mouse_x = MouseX ()
	;If the_new_mouse_x <> current_mouse_x
		;do_update = True
		the_mouse_x_speed = the_new_mouse_x - current_mouse_x
		current_mouse_x = the_new_mouse_x
	;EndIf

	the_new_mouse_y = MouseY ()
	;If the_new_mouse_y <> current_mouse_y
		;do_update = True
		the_mouse_y_speed = the_new_mouse_y - current_mouse_y
		current_mouse_y = the_new_mouse_y
	;EndIf

	mouse_x_speed_5# = mouse_x_speed_4#
	mouse_x_speed_4# = mouse_x_speed_3#
	mouse_x_speed_3# = mouse_x_speed_2#
	mouse_x_speed_2# = mouse_x_speed_1#
	mouse_x_speed_1# = the_mouse_x_speed

	mouse_y_speed_5# = mouse_y_speed_4#
	mouse_y_speed_4# = mouse_y_speed_3#
	mouse_y_speed_3# = mouse_y_speed_2#
	mouse_y_speed_2# = mouse_y_speed_1#
	mouse_y_speed_1# = the_mouse_y_speed

	If ( mouse_x_speed_1# > 0.1 ) Or ( mouse_y_speed_1# > 0.1 ) Then do_update = True

	the_yaw# = ( ( mouse_x_speed_1# + mouse_x_speed_2# + mouse_x_speed_3# + mouse_x_speed_4# + mouse_x_speed_5# ) / 5.0 ) * mouselook_x_inc#

	the_pitch# = ( ( mouse_y_speed_1# + mouse_y_speed_2# + mouse_y_speed_3# + mouse_y_speed_4# + mouse_y_speed_5# ) / 5.0 ) * mouselook_y_inc#

	TurnEntity user, 0.0, -the_yaw#, 0.0
	user_camera_pitch# = user_camera_pitch# + the_pitch#
	If user_camera_pitch# > 90.0 Then user_camera_pitch# = 90.0
	If user_camera_pitch# < -90.0 Then user_camera_pitch# = -90.0
	RotateEntity user_camera, user_camera_pitch#, 0.0, 0.0

End Function

ok, cheers! guys..i will try this stuff out l8r ;)
...