I'm not sure if there's an existing extension for this, but I use this kind of in my extension. Neither am I sure if my method is easiest way to go, it's quiet computing-intensive if you're solid is made out of many faces.

NOTE: a line is infinite long in both directions and a half line is infinite long in one direction.

It is based on the principle that a half line that starts in your point should intersect your solid an odd number of times. So you have to check every face of the solid if it intersects with the half line.

Method intersect_line_plane calculates the intersection of the line (in both directions) and the plane of the face. You have to check if the intersection is on the half line and on the face of the plane.

For checking if the intersection is part the face again it can be done with another half line which starts in the intersection and is parallel to the plane of the face. Once again the intersection is part of the face if the half line intersects the edges of the face an odd number of times. So you should check every edge of the face and see if the half line intersects it. The method intersect_line_line calculates the intersection between the line of the half line and the line of the edge. Check if this intersection is part of the half line and the edge.

Hopefully this is helpfull to you, it may be fomulated a little chaotic. I can share some of my code if you want.

@unknownuser said:

It sounds like you are using your own intersection algorithm(?)

The intersection of the lines is calculated with the Geom.intersect_line_line method. Next I use my own calculations to see if the edges on these lines also intersect.

The problem is solved by using arrays, thanks for your help.

How do I avoid rounding when using the Point3d.[] or Point3d.x/y/z methods?

Here's an example where I experience the problem. I have 3 Point3d's that are part of a line:

• edge_start = (-29,389263mm, 0mm, -40,45085mm)* edge_end = (-40,45085mm, 0mm, -29,389263mm) * intersection = (-40,458747mm, 0mm, -29,381365mm)

I want to run a piece of code if the intersection is on the edge. I have an if-statement that should work, but it fails when two points are close by because of the rounding of the Point3d.[] and Point3d.x/y/z methods.

edge_end.x should be greater then intersection.x, but it rounds edge_end.x to ~-40.5mm and also intersection.x to ~-40.5mm. This makes the variables equal to eachother.

How do I compare the x values of a Point3d without losing the precision?

@sdmitch said:

You are scaling from the ORIGIN in both cases?

My excuses if it's a common thing to know, but I don't know exactly what you mean by 'scaling from the origin'.

I did create both boxes which are created as groups. Next I scaled them 'Red Scale about Opposite Point' with the Scale tool in negative x-direction (scaling factor 2).

@slbaumgartner said:

This begs the question: why not upgrade to the latest SketchUp Make 2015, which uses Ruby 2.0 and includes standard libraries such as matrix?

I use the software provided by the company I work for. I can ask if they don't have any keys for a more recent version, but I doubt it.

When I create shapes in Sketchup and start rotating and moving them my code is perfectly able to calculate the new position of the shape. The calulations are made by using the dimensions of the original bounding box and the transformation matrix.

Everything goes fine, until I start scaling the shape. In order to understand what goes wrong when I scale an object I did some scaling on easy shapes. The matching transformation matrices with the shapes gave results that did not make any sense for me. Here's one of the tests I did:

First I did create a box with begin coordinates (0,0,0) and width(X)/length(Y)/height(Z) (20,20,20). Next I scaled the box with value 2 in negative x-direction. This gave me a box with begin coordinates (-20,0,0) and W/L/H (40,20,20). This is the matching transformation matrix

[2.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, -20, 0.0, 0.0, 1.0]

The matrix makes perfect sense for this example.

For my next example I did create a box with begin coordinates (40,40,40) and W/L/H (20,20,20). Once again I scaled the shape with value 2 in negative x-direction. This gives a box with begin coordinates (20,40,40) and W/L/H (40,20,20). This is the matching transformation matrix

[2.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0, -60, 0.0, 0.0, 1.0]

I can't find any reasonable explanation for the -60. I think it would be -20 as the other box.

Can someone explain me how this is possible?

@dan rathbun said:

You realize that this topic thread is like 4 and 1/2 years old ?

Yes, I have seen it. That does not mean that people can't come here and look for code that works? That's how I landed here. I was looking for some code that could convert the rotation matrix to euler angles. I found out that this code didn't work for me, so I did correct it and now I share it here just in case people experience the same problem as me. I'm just excited that I finally can contribute a little instead of always asking things!

Nothing wrong with that, right?

In my calculations I have to do a matrix multiplication. Instead of doing this calculation of every element I want to use the base ruby class Matrix which is made for such operations. I found out that it's not just adding require 'matrix' to your code.

I did copy the matrix.rb and e2mmap.rb (which is required by matrix.rb) from the ruby2.2.2 folder to the plugin folder from SketchUp where also my main script is located. Next thing I did is add this line require File.join(File.dirname(FILE), 'matrix.rb') to my main script and this line require File.join(File.dirname(FILE), 'e2mmap.rb') in matrix.rb. I believe this is the right way to require 'matrix'.

The thing is, when I load my main script in SketchUp I get a bunch of error messages and my script still won't do any matrix calculations. Here's the list of errors:

Error Loading File matrix.rb
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;573; odd number list for Hash
  SELECTORS = {all; true, diagonal; true, off_dia...
                   ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;573; syntax error, unexpected ';', expecting '}'
  SELECTORS = {all; true, diagonal; true, off_dia...
                   ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;573; Can't assign to true
  SELECTORS = {all; true, diagonal; true, off_diagonal;...
                         ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;573; syntax error, unexpected ';', expecting '='
...ECTORS = {all; true, diagonal; true, off_diagonal; true, low...
                              ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;573; Can't assign to true
... = {all; true, diagonal; true, off_diagonal; true, lower; tr...
                              ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;573; syntax error, unexpected ';', expecting '='
... diagonal; true, off_diagonal; true, lower; true, strict_low...
                              ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;573; Can't assign to true
...nal; true, off_diagonal; true, lower; true, strict_lower; tr...
                              ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;573; syntax error, unexpected ';', expecting '='
...ue, off_diagonal; true, lower; true, strict_lower; true, str...
                              ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;573; Can't assign to true
...f_diagonal; true, lower; true, strict_lower; true, strict_up...
                              ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;573; syntax error, unexpected ';', expecting '='
...ue, lower; true, strict_lower; true, strict_upper; true, upp...
                              ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;573; Can't assign to true
...wer; true, strict_lower; true, strict_upper; true, upper; tr...
                              ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;573; syntax error, unexpected ';', expecting '='
...ict_lower; true, strict_upper; true, upper; true}.freeze
                              ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;573; Can't assign to true
...wer; true, strict_upper; true, upper; true}.freeze
                              ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;573; syntax error, unexpected ';', expecting '='
...ue, strict_upper; true, upper; true}.freeze
                              ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;717; syntax error, unexpected ';', expecting ')'
  def laplace_expansion(row; nil, column; nil)
                            ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;717; Can't assign to nil
  def laplace_expansion(row; nil, column; nil)
                                 ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;717; syntax error, unexpected ';', expecting '='
  def laplace_expansion(row; nil, column; nil)
                                         ^
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;1535; module definition in method body
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;1561; module definition in method body
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;1603; class definition in method body
C;/Program Files (x86)/Google/Google SketchUp 8/Plugins/matrix.rb;1673; syntax error, unexpected kEND, expecting $end

I think I already have a solution for my problem. I'm only going to use the multiplication class method. So I can maybe delete all the rest from matrix.rb, so the lines where the errors occur are gone. I can also code the calculation of a 3x3 matrix * 3x1 matrix by myself. But I just want to know why I can use the Matrix class in powershell and not in SketchUp. I'm think it has someting to do with my older version of SketchUp (8)?

I did delete the rotX/Y/Z methods, that's why I didn't understand where the variable xyz came from and why it could get value = 0/1/2. I do understand how methods with there variables work. Sorry was confused.

On the other hand, I have been working with the euler_angle method for a while and now that I'm closely getting to a complete script I have noticed this method only partial works (for me?). Does it work for you guys? When I did draw shapes with a given rotation, the method didn't succeed to calculate the right angles for me so I did some research and made some changes. Here's the code I use:

	def self.rotation(trans)
		b = [trans.xaxis.to_a, trans.yaxis.to_a, trans.zaxis.to_a]
		m = b.transpose.flatten!
		if m[6] != 1 and m[6] != -1
			ry = -Math.asin(m[6])
			rx = Math.atan2(m[7]/Math.cos(ry),m[8]/Math.cos(ry))
			rz = Math.atan2(m[3]/Math.cos(ry),m[0]/Math.cos(ry))
		else
			rz = 0
			phipos = Math.atan2(m[1],m[2])
			phineg = Math.atan2(-m[1],-m[2])
			if m[6] == -1
				ry = Math;;PI/2
				rx = rz + phipos
			else
				ry = -Math;;PI/2
				rx = -rz + phineg
			end
		end   
	return [rx.radians,ry.radians,rz.radians]
	end	

First I found this document (page 5) that explains the calculations the way you do it. But it seems that you miss little pieces of code to make it complete.

When I did calculate the angles it yet didn't calculate the right angles. So I did try some things and found out that the angles that were calculated represent the transpose matrix of the rotation that I need. So I fixed this by transposing the rotation matrix before the calculations.

With these changes this piece of code does calculate the right angles. Did your code work for you?

I think I might be able to help you, but I'm a afraid I don't understand very well what you want to realize. Correct me if I'm wrong:

So you create a rectangle as a group and want an easy way to change the size of the rectangle?

If this is the case, I might be able to help you! I believe you are looking for UI.inputbox