cross product question

Blitz3D Forums/Blitz3D Programming/cross product question

MadsNy

(Posted 2004) [#1]

hi.. I have a borring math problem and im a visual person.. i need to draw a line between to points in a 3D space.. out of this line i want to place a quad so it's 90 degrees on the line...
the direction will at my first attemp be random... so i would also need to be able to rotate the quad around the line, but so that it still is 90 degree on the line..

i guess the trick is dross product.. and that i did make.. but look at my code.... why aren't the BLUE object not always 90 on the two RED and GREEN line.. ???...
(press a and the will shift RND)

what are my doing wrong and how to fix it.. :) help any one. :)

Graphics3D 640,480, 0, 2
SetBuffer BackBuffer()
cam = CreateCamera()
PositionEntity cam, 50,50,50
CameraClsColor cam, 255,255,255

o1 = CreateCube()
ScaleEntity o1, 1,1,10
EntityColor o1, 255,0,0
o2 = CreateCube()
ScaleEntity o2, 1,1,10
EntityColor o2, 0,255,0
o3 = CreateCube()
ScaleEntity o3, 1,1,10
EntityColor o3, 0,0,255


v1x# = 10
v1y# = 5
v1z# = 28

v2x# = 1
v2y# = 5
v2z# = 40

v3x# = 0
v3y# = 0
v3z# = 0



Repeat
	MoveEntity cam, 2,0,0
	PointEntity cam, o1
	CameraClsMode cam, True, True
	
	AlignToVector o1, v1x, v1y, v1z, y
	AlignToVector o2, v2x, v2x, v2z, y
	If KeyHit(30) Then
		v2x# = Rnd(-10,10)
		v2y# = Rnd(-10,10)
		v2z# = Rnd(-10,10)
	End If	
	
	;Cross product
	cx# = ( v1y * v2z ) - ( v1z * v2y ) 
	cy# = ( v1z * v2x ) - ( v1x * v2z ) 
	cz# = ( v1x * v2y ) - ( v1y * v2x )
	
	
	AlignToVector o3, cx,cy,cz, y
	
	
	RenderWorld
	Flip()	
Until KeyHit(1)
End

;				;code snippet from Jeppe Nielsen.. thx
;
;				;Cross product
;				cx# = ( dy1 * dz2 ) - ( dz1 * dy2 ) 
;				cy# = ( dz1 * dx2 ) - ( dx1 * dz2 ) 
;				cz# = ( dx1 * dy2 ) - ( dy1 * dx2 ) 				
;															
;				AlignToVector c\pivot,cx,cy,cz,1

Augen

(Posted 2004) [#2]

You have
AlignToVector o1,v2x,v2x,v2z, y

EDIT: i meant to put o2 where the o1 is.

Where is the v2y?

This probably has nothing to do with what you asked.