WorldViz User Forum  

Go Back   WorldViz User Forum > Vizard

Reply
 
Thread Tools Rate Thread Display Modes
  #1  
Old 04-20-2008, 09:12 PM
chris chris is offline
Member
 
Join Date: Apr 2008
Posts: 2
simply overlapping objects

hey guys, this should be relatively easy but I cna't figure it out.

Basically I have a set of arbitrary points and a plane that I need to put within the field of points. The thing is, the user can select 3 points and the plane has to align itself with them.

as a simple solution I thought to draw a triangle (triangle_strip) connecting the points and then take it's rotation/position and apply it to the plane (which at this point has been created, just a bunch of triangle strips).

The thing is, is I can't figure out how to do that. I've been messing around with the orientation and rotation of various things and regardless of what I try nothing works. I've tried getting the objects euler, matrix, quat and axis angle, none of which have worked (and actually all are the same for the two objects, who are in two different initial positions and orientations).

So I'm not sure that I can grab the triangles rotation, as I haven't explicitly applied one to it yet. I was just wondering if I'm on the right track, or if I'm overlooking something extremely obvious.

Any help would be appreciated.
thanks
Reply With Quote
  #2  
Old 04-21-2008, 07:27 PM
farshizzo farshizzo is offline
WorldViz Team Member
 
Join Date: Mar 2003
Posts: 2,849
You will need to use some 3D math to determine the orientation of the triangle. Here is some code that will return the transormation matrix of a triangle, given 3 points:
Code:
import viz
viz.go()


P1 = [-1,1,2]
P2 = [-0.1,2,2.5]
P3 = [1,0.1,2.3]


def GetTriangleMatrix(p1,p2,p3):
	
	#Get vector of p1 to p2
	v1 = viz.Vector(p2) - viz.Vector(p1)
	
	#Get vector of p1 to p3
	v2 = viz.Vector(p3) - viz.Vector(p1)
	
	#Take cross product to determine normal of triangle
	normal = v2 ^ v1
	
	#Determine rotation by rotating forward vector to normal
	m = viz.Matrix()
	m.makeVecRotVec([0,0,1],normal)
	
	#Set position of matrix to center of triangle
	p = viz.Vector(p1) + viz.Vector(p2) + viz.Vector(p3)
	m.setPosition( p / 3.0 )
	
	#Return the transformation matrix
	return m
	
	
#Draw triangle
viz.startlayer(viz.TRIANGLES)
viz.vertexcolor(viz.RED)
viz.vertex(P1)
viz.vertex(P2)
viz.vertex(P3)
viz.endlayer()

#Get matrix of triangle
m = GetTriangleMatrix(P1,P2,P3)

#Create arrow to show triangle rotation/translation
arrow = viz.add('marker.wrl')
arrow.setMatrix(m)

#Setup pivot camera
import vizcam
vizcam.PivotNavigate(center=m.getPosition(),distance=10)

#Add ground
viz.add('tut_ground.wrl')
Reply With Quote
  #3  
Old 04-27-2008, 04:50 PM
chris chris is offline
Member
 
Join Date: Apr 2008
Posts: 2
Wow that's exactly what I needed thanks!

I also didn't know about ^, that makes life a bit easier.

However this brings up another issue.

While my actual project is a bit more complex then the example I asked for, the solution transfered to it extremely well. The issue now is I'm applying this transformation matrix to an on the fly object, which in itself works, however the transformation is applied at the objects current center, which geometrically is not its center at all. All attempts at object.center have failed.

I was wondering if there was a simple solution for this one.
Reply With Quote
  #4  
Old 04-28-2008, 12:39 PM
farshizzo farshizzo is offline
WorldViz Team Member
 
Join Date: Mar 2003
Posts: 2,849
The best solution is to create the triangles so their geometric center corresponds to the origin (0,0,0). Is this not a viable option for you?
Reply With Quote
Reply

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Could not find plugin to load objects... halley Vizard 1 05-30-2006 11:01 AM
putting objects on the screen jargon Vizard 7 05-24-2005 11:31 AM
Changing the Color of On-the-Fly Objects vjosh Vizard 1 01-04-2005 11:48 PM
limits on number of objects benelux Vizard 3 07-22-2004 01:26 PM
3D sound & child objects FlyingWren Vizard 1 09-19-2003 12:13 PM


All times are GMT -7. The time now is 04:19 PM.


Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2024, vBulletin Solutions, Inc.
Copyright 2002-2023 WorldViz LLC