Roller coaster animation - move TO and angle of edge

Nask

Hi all,

I am trying to make a model to animate a kind of roller coaster.

Step 1: Select the cart and the path (loose edges) and define which is the cart and what are the edges.

Step 2: Put the edges in order and put them in a array

Step 3: Depending on the time, calculate where the cart should be on the track

Step 4: Move the cart TO the start of the edge it should be

Step 5: Move the cart BY the amount it has already travelled on the edge

Step 6: Rotate the cart TO rotx,y,z = 0

Step 7: Rotate the cart to match rotx, roty and rotz of the edge

My problems start at step 5. I only know how to move by a certain amount, but not how to move to a certain point, whatever the start position was. I thought to do this using a Point3D instead of vector3d object, but this does not work.

The same I have to solve for the rotation.

Then the last question is whether you can get the angles of an edge in an easy way, so without calculating them from the coordinated of start and end point.

Can you guys help me out here?

See below the test code I wrote for the move TO and move BY

model = Sketchup.active_model
ents = model.entities
face= ents.add_face [0,0,0],[5,0,0],[5,5,0], [0,5,0]
face_group = ents.add_group face


clock = 0

timer_id = UI.start_timer(0.1, true) {
     
 if clock <= 100 
   vvMoveToPoint = [0,0,0]
   point = Geom;;Point3d.new vvMoveToPoint
   t1 = Geom;;Transformation.new point 

   vvMoveByVector = [clock/10,clock/10,0]
   vector= Geom;;Vector3d.new vvMoveByVector 
   t2 = Geom;;Transformation.new vector

   t_all = t1 * t2

   face_group = face_group.transform! t_all

 else
   UI.stop_timer timer_id
   puts "clock is larger than 5 " + clock.to_s
      
 end

   clock = clock + 1  
}

Here I laready tried things like changing the order of t1 and t2...

EDIT: I now also tried to get the coordinates of the group with position, but that doesnt work, I have tried to make a bound for the group and get the position of the bound box, but that doesnt work neither. Maybe I have to save in a variable which tranlations and rotations I have done with the group, but that seems strange.. SU should have some information of where the group is, no??

EDIT 2: I got the thing working, but with the method where I store the performed transformation in variables, to transform it back later. I supose there are better ways to do this, so I am open for suggestions... The challenge I have now is to introduce several carts that travel together, so I will be busy for a while..


model = Sketchup.active_model
ents2 = model.entities
ents = model.selection # selection in future

viNumberOfEdges = ents.count-1
puts "NumberOfEdges" + viNumberOfEdges.to_s

cart = ents.find { |ent| ent.typename.to_s == "ComponentInstance"}
path = []
path = ents

path.remove [cart]

vesPath = []

path.each {|item|

	if item.typename=="Edge"
		vesPath = vesPath + [item]
	end }


puts "First element of vesPath" + vesPath[4].to_s

vesOrderedPath = []

vesOrderedPath = vesOrderedPath + [vesPath[0]] #First element has to be filled, but not used
vesOrderedPath = vesOrderedPath + [vesPath[0]]

vesPath = vesPath - [vesOrderedPath[1]]

i = 1

veLast = vesOrderedPath[1]

while i <=  viNumberOfEdges

	vvEnd = veLast.end
	veNext = vesPath.find {|edge| edge.start == vvEnd || edge.end == vvEnd } 
	vesOrderedPath = vesOrderedPath + [veNext]
	vesPath = vesPath - [veNext]
	veLast = veNext

	i = i + 1
end


i = 1
ents2 = model.entities
vrsLength = [0]
vrsLengthAcc = [0]
vrTotalLength = 0.0
vrLength = 0.0


while i <= vesOrderedPath.size-2 
	
	vrLength = vesOrderedPath[i].length
	vrsLength = vrsLength + [vrLength]
	vrTotalLength = vrTotalLength + vrLength
	vrsLengthAcc = vrsLengthAcc + [vrTotalLength]


	i = i + 1
end


 vrSpeed = 0.1

 posCartx = 0.0
 posCarty = 0.0
 posCartz = 0.0

 rotx = 0.0
 roty = 0.0
 rotz = 0.0
 clock = 0.0

 timer_id = UI.start_timer(0.5, true) {
  


 if clock <= 500 



	# define vector to get back to origin
	vvMoveToPoint = [-posCartx ,-posCarty ,-posCartz ]
	point = Geom;;Point3d.new vvMoveToPoint
	t0 = Geom;;Transformation.new point 

	# define rotation back
	trb_x = Geom;;Transformation.rotation [posCartx ,posCarty ,posCartz],
													  [1, 0, 0],-rotx

	
	trb_z = Geom;;Transformation.rotation [posCartx ,posCarty ,posCartz],
													[0, 0, 1],-rotz


	# define starting point
	
		
	vrDistInLap = clock*vrSpeed%vrTotalLength

	vrTemp = vrsLengthAcc.find {|acc| acc>vrDistInLap}

	viEdgeID = vrsLengthAcc.index vrTemp 

	vrTravelledOnOtherEdges = vrsLengthAcc[viEdgeID -1]
	vrTravelOnEdge = vrDistInLap - vrTravelledOnOtherEdges

	veCurrentEdge = vesOrderedPath[viEdgeID] 

	px = veCurrentEdge.start.position.x
	py = veCurrentEdge.start.position.y
	pz = veCurrentEdge.start.position.z


	vvMoveToPoint = [px,py,pz]
	point = Geom;;Point3d.new vvMoveToPoint
	t1 = Geom;;Transformation.new point 

	# update location
	posCartx = px 
	posCarty = py 
	posCartz = pz 
	
	# define vector
   
	factor = ( vrTravelOnEdge/ veCurrentEdge.length.to_inch)

    vx_tot = veCurrentEdge.end.position.x.to_inch - veCurrentEdge.start.position.x.to_inch
    vy_tot = veCurrentEdge.end.position.y.to_inch - veCurrentEdge.start.position.y.to_inch
    vz_tot = veCurrentEdge.end.position.z.to_inch - veCurrentEdge.start.position.z.to_inch

	vx = vx_tot * factor
	vy = vy_tot * factor
	vz = vz_tot * factor
    

	vvMoveByVector = [vx,vy,vz]
	vector= Geom;;Vector3d.new vvMoveByVector 
	t2 = Geom;;Transformation.new vector
	
	posCartx = posCartx + vx 
	posCarty = posCarty + vy 
	posCartz = posCartz + vz 

	rotx = Math.asin(vz_tot/veCurrentEdge.length.to_inch)

	tr_x = Geom;;Transformation.rotation [posCartx ,posCarty ,posCartz],
													[1, 0, 0],rotx

	rotz = Math.asin(vx_tot/veCurrentEdge.length.to_inch)
    if vy > 0 
		rotz = -rotz
    end
    

	tr_z = Geom;;Transformation.rotation [posCartx ,posCarty ,posCartz],
													[0, 0, 1],rotz
	


	t_all = tr_z * tr_x * t2 * t1 * t0 * trb_x * trb_z

	cart = cart.transform! t_all



 else
	UI.stop_timer timer_id
	puts "clock is larger than 5 " + clock.to_s
		
 end

	clock = clock + 1  
}

Code only works when you select one group (block that is centered on the origin) and a loop of edges before executing it

MartinRinehart

My tutorial, Chapter 16 has library code to handle this. You may be able to go straight to Chapter 16 and get your work done. But as TIG points out (reincarnated as the wise old one at the fairytale SketchUCation tavern) that has its drawbacks.