Trigger

Blitz3D Forums/Blitz3D Programming/Trigger

Mathieu A

(Posted 2004) [#1]

How could we make a Box trigger in blitz? Because if we use a collision box, there will a collision. I just want to know if the plyer is inside a Box.

eBusiness

(Posted 2004) [#2]

You will probably need to make your own position check, If the box is not rotated in too many dimensions, this shouldn't be that hard.

Zethrax

(Posted 2004) [#3]

The code below should get you started. I haven't tested it, though, so it may not work as is. I've used 'Then If' instead of 'And' so that the test will abort early if any of the checks fail (Using 'And' would cause the entire series of checks to be tested even if an early check failed).


If EntityX#( player ) < high_x# Then If EntityX#() > low_x# Then If EntityY#() < high_y# Then If EntityY#() > low_y# Then If EntityZ#() < high_z# Then If EntityZ#() > low_z#

; Player's centerpoint is inside box.

EndIf

If the range box is rotated relative to global space (and assuming it has a pivot or some other type of entity that you can use as a reference which is axially aligned in its local space) then you can map the centerpoint of your player to the range box's local space, using 'TFormPoint', before doing your range-checking.


TFormPoint EntityX#( player ), EntityY#( player ), EntityZ#( player ), 0, range_check_reference_entity

If TFormedX() < high_x# Then If TFormedX() > low_x# Then If TFormedY() < high_y# Then If TFormedY() > low_y# Then If TFormedZ() < high_z# Then If TFormedZ() > low_z#

; Player's centerpoint is inside box.

EndIf

Techlord

(Posted 2004) [#4]

Assuming your in need of a simple box trigger with no regard to orientation. Here are
3 box collision check algos

If playerx<boxmaxx And playerx>boxminx
	If playery<boxmaxy And playery>boxminy
		if playerz<boxmaxz And playerz>boxminz
			Return True
		Endif
	EndIf
EndIf

If playerx<boxx+boxwidth And playerx>boxx
	If playery<boxy+boxheight And playery>boxy
		if playerz<boxz+boxdepth And playerz>boxz
			Return True
		Endif
	EndIf
EndIf

If playerx<boxx+boxhalfwidth And playerx>boxx-boxhalfwidth
	If playery<boxy+boxhalfheight And playery>boxy-boxhalfheight
		if playerz<boxz+boxhalfdepth And playerz>boxz-boxhalfdepth
			Return True
		Endif
	EndIf
EndIf

I recommend cascading the condition check for speed.