REQ: Checking if components (solids) intersect

Bobvandevoort

Hi everyone,

So I haven't been able to find a plugin that checks something crucial in my opinion.
If you are designing a 3D object with movable parts it can sometimes be very important to check if solids (or components) intersect (or maybe touch). This is especially important if you have a high number of parts or moving parts. An example I can give of this is something I'm working on, it is a puzzle box.A puzzle box is a box that has sliding components on different sides on the box, called sliders. If you move when one these sliders you want ot be sure it doesn't get blocked by another part (aka intersecting), because if it's unintentionally blocked than you can't open the box.

Something that would be even more usefull is if a part(component) could be moved (or rotated)along an axis until some part of it hits another component (this would make checking even easier).

This can ofcourse be applied to much more cases, mostly mechanisms that need to be check if they having moving parts, a clock, a model engine, etc. To see if the device can actually operate.

In the pdf file ans skp you can see what I mean with intersecting and touching.
Intersecting1.pdf
Intersecting.skp

It would be even handier (also has a lot of other applications in building models) if you can move a component along the axes (either positive or negative) until it touches the next piece (component) and have it stop there. This easily shows if it can move along the intended path.
It should check inner components touching and not just the surrounding (encompassing) parent component boxes.

glro

component check
https://docs.google.com/file/d/0Bw8zdmaKDWIfNzdiNmQ5MmItOGJhNC00MzY1LWJmNjYtMzhlYWY3NzliYTkx/edit?hl=en_US%26amp;pli=1

does part of the job you are asking for, as far as i understand

detection based on the bounding box position is relatively easy to achieve, so this plugin could be hacked in the way you want it

but if the component is not square, it is much more difficult

you can also try SUsolid
http://www.susolid.com/

this plugin can detect any intersection of components, even if not square, but they must be solids

Box

You might find Sketchy Physics useful.
You could make your puzzles function and if they jam up you know there is a problem.

Bobvandevoort

Thank you guys very much, the combination of SuSolid and Sketchy Physics should do the trick.

Once I finish my work I'll show it

Bobvandevoort

Oh btw if anyone has anymore more suggestions please share them.

(using Sketchy Physics is going to be a lot of work, btw anyone no how to make objects only move when you drag/click them, so that they don't react to gravity)

Box

You can turn gravity off or make it stronger etc in the Physics settings.

Although it's worth noting what happens in 0 gravity.

TIG

Assuming they do/could overlap, then you need to check for geometry intersections.
Try this - you pass two arguments - references to a group or component-instance - returns ' true' if they do intersect|touch, or ' false' if there is no intersection [or 'nil' if incorrect arguments]: e.g. TIG.intersect?(e1, e2)

module TIG
	def self.intersect?(e1=nil, e2=nil)
		if e1.is_a?(Sketchup;;Group) || e1.is_a?(Sketchup;;ComponentInstance)
			if e1.is_a?(Sketchup;;Group)
				es1 = e1.entities
			else
				es1 = e1.definition.entities
			end
			fail = false
		else
			fail = true
		end
		if e2.is_a?(Sketchup;;Group) || e2.is_a?(Sketchup;;ComponentInstance)
			fail = false
		else
			fail = true
		end
		if fail
			puts("#{self}.intersect? requires references to two groups/component-instances.\nReturns 'true' [intersecting || touching] or 'false'.")
			return nil
		end
		ens = e1.parent.entities
		tr1 = e1.transformation
		grp = ens.add_group()
		grp.transform!(tr1) ### so can see cut lines IF erase! is disabled at the end !
		ges = grp.entities
		es1.intersect_with(true, tr1, ges, tr1, true, e2)
		if ges[0]
			int = true
		else
			int = false
		end
		grp.erase!
		return int
	end
end

Note that they do not need to be 'solids', but a check for that could be added...

Bobvandevoort

@tig said:

Assuming they do/could overlap, then you need to check for geometry intersections.
Try this - you pass two arguments - references to a group or component-instance - returns ' true' if they do intersect|touch, or ' false' if there is no intersection [or 'nil' if incorrect arguments]: e.g. TIG.intersect?(e1, e2)

module TIG
> 	def self.intersect?(e1=nil, e2=nil)
> 		if e1.is_a?(Sketchup;;Group) || e1.is_a?(Sketchup;;ComponentInstance)
> 			if e1.is_a?(Sketchup;;Group)
> 				es1 = e1.entities
> 			else
> 				es1 = e1.definition.entities
> 			end
> 			fail = false
> 		else
> 			fail = true
> 		end
> 		if e2.is_a?(Sketchup;;Group) || e2.is_a?(Sketchup;;ComponentInstance)
> 			fail = false
> 		else
> 			fail = true
> 		end
> 		if fail
> 			puts("#{self}.intersect? requires references to two groups/component-instances.\nReturns 'true' [intersecting || touching] or 'false'.")
> 			return nil
> 		end
> 		ens = e1.parent.entities
> 		tr1 = e1.transformation
> 		grp = ens.add_group()
> 		grp.transform!(tr1) ### so can see cut lines IF erase! is disabled at the end !
> 		ges = grp.entities
> 		es1.intersect_with(true, tr1, ges, tr1, true, e2)
> 		if ges[0]
> 			int = true
> 		else
> 			int = false
> 		end
> 		grp.erase!
> 		return int
> 	end
> end

Note that they do not need to be 'solids', but a check for that could be added...

That seems really nice and cool but I've never worked with ruby nor the ruby interface in sketchup.
I do have some basic coding skills in C (and some other languages).

Does it matter that instead of having groups that I have components (as far as I understood it doesn't).

SUSolids sees all my components as solids at the moment so if that is what you mean by solid than yes all my components are solids.

Furthermore I understand the code more or less up till the checking if there're actually 2 components selected. After that it's a bit unclear how it checks for the intersection (it seems like you're using the intersection tool but the arguments are unclear).

Further it should be possible to just use a for loop to check the whole model for intersections right?

One other thing would it be possible to check for only touching between just 2 components (multiple would be better) in a certain plain (of 1 of the components).

So let me explain that a bit more correctly by first telling what I want to use the check for. I want to make a move command/script/tool that moves 1 a component along an axis (both direction being possible) until it collides with another surface/component. This means that if a component is moved along the x-axis it should only look if it's touching any other components in the x-direction (or an yz-plane). Meaning if I have a rod in a cylinder with their longitudinal axis in the x-axis and I let the rod be moved/translated along the x-axis than even if their walls are touching in the y or z direction it should stop the translation. The translation should be stopped as soon as an intersection or a touch at base of the rod touches and yz-plane is detected.

TIG

My example code checks if any two given groups OR component-instances 'intersect'.
It only works if the two things are in the same entities context, but I assume you haven't nested things...
So TIG.intersect(e1,e2) returns 'true' or 'false' if they intersect|touch or if they are separate, it returns 'nil' if you pass wrong arguments.
They do not need to be solids for this test.
To test all objects in a context try this [NOTE: you also need to have pre-loaded the ' TIG.intersect? code !]

module TIG
	def self.intersectALL()
		model=Sketchup.active_model
		ss=model.selection
		ents=model.active_entities
		ss.clear
		gps=ents.grep(Sketchup;;Group)
		ins=ents.grep(Sketchup;;ComponentInstance)
		ens=gps+ins
		ens.uniq!
		ens.compact!
		(ens.length-1).times{|i|
			(ens.length-1).times{|j|
				next if j==i
				if self.intersect?(ens[i], ens[j])
					ss.add(ens[i])
					ss.add(ens[j])
				end
			}
		}
		puts "Any intersecting groups/component-intsnces are highlighted..."
	end
end

To run it use TIG.intersectALL
All groups/component-instances that intersect or touch are highlighted...
It highlights all groups/component-intsances that intersect...

Bobvandevoort

Hey TIG,

Thanks a lot again that is really helpful

Three more things though, one I do have nested components (otherwise my model is unmanageble) which makes it troublesome to use it like this in my final script. (btw I only use components)

Secondly what if I just want to find intersecting components (groups/element) and not also touching ones.

The last thing is I now understand both codes except for a part concerning the first script

  grp = ens.add_group()
      grp.transform!(tr1) ### so can see cut lines IF erase! is disabled at the end !
      ges = grp.entities
      es1.intersect_with(true, tr1, ges, tr1, true, e2)
      if ges[0]
         int = true
      else
         int = false
      end

A few things here, sometimes the intersection lines fail to show up. (this is when I have nested component but these components are not touching or intersecting anything)

the intersect_with is still unclear to me.
we make a group of the first entity 1 which we call grp
then do a transformation (now is this a simple translation or a true transformation and how should I envision that in skp)
We say ges= the entities that were transformed
Now we intersect all the entities in ges with e2, which if an intersect occurs removes all elements from ges as for as I understand. However what's the reason the es1.intersect_with.

Also why can't we by example use something like this



result = e1.intersect(e2)
if result == nil
   int = false
else 
    int = true

Please keep in mind this is my first time doing any programming in ruby and for SU, so I had to read up on some of the coding before I could reply.

Thank you very much for the help

TIG

My 'simple' example expects both of the passed objects [group/component-instance] to be in the same context - just as you might when doing the intersection manually on two selected objects.
If they are not in the same entities-context they probably won't intersect logically, unless you somehow apply both of their 'transformations' in the intersection-tests - I'll have to think about that...

Here's a breakdown of the code...

grp = ens.add_group() This adds a temporary group to contain the intersection edges, if any
grp.transform!(tr1) ### so can see cut lines IF erase! is disabled at the end ! It's as the ### note says - it moves the intersection lines back to where you'd expect them to be, rather than at the ORIGIN - if you erase! the grp you never see it...
ges = grp.entities A reference to the grp entities context
es1.intersect_with(true, tr1, ges, tr1, true, e2) The complicated 'intersect_with' - the first passed group/component-instance 'e1' [referenced earlier as 'es1'] is intersected with the second passed group/component-instance 'e2' [final argument in the ()], the other arguments in the () are 'true' to tell it to put the intersected geometry into another context, 'ges' sets the destination of the intersected geometry [the grp's entities], 'tr1' the transformation of 'e1', 'true' to include any hidden objects in the intersection, and as mentioned before 'e2' the second object that is being intersected with...
if ges[0] int = true else int = false end This final part tests for any entities inside the 'grp' entities-context 'ges': if so 'int' is 'true' otherwise it's 'false'...
Not included in your snippet - it then does grp.erase! to remove the temporary group, and return 'int'...

It would be difficult to test for a full intersection rather than a touching.
If you make two box groups and place them so the definitely overlap and select them and do a context-menu 'intersect-selection' you'll get a set of edges - visible if you move the two groups away.
If you move a group so that 'kiss' - i.e. touch on a face - and repeat the intersect-selection, you still get geometry where they touch.
There is no easily identifiable difference between the two - the full-intersection set is clearly '3d' BUT a touching set of edges could be equally complex...

The only way to test otherwise... is to consider every vertex in a group and see if its position [adjusted for the container's transformation AND the potentially intersected second container's transformation] is inside the second object - probably with a 'raytest'.
But even then it'd be quite possible to intersect two objects in such a way that no vertices from one are inside the other, BUT a true intersection still exists !

Any suggestions on how a full-intersection versus a touching-intersection can be determined would be appreciated...

Bobvandevoort

Thanks for the really awesome explanation.

I know a way that works (and just finished writing it) however it requires the pro version.

I wrote it "ruby code editor" plugin and there for used the selection in the model to set the two components. (link http://www.alexschreyer.net/projects/sketchup-ruby-code-editor/)

it works good so far only got a little error when I try to turn the material red of the intersecting component part.

mod = Sketchup.active_model # Open model
ent = mod.entities # All entities in model
sel = mod.selection # Current selection
 instance1 = sel[0]
 instance2 = sel[1]
 ci_def = instance1.definition 
 tr1 = instance1.transformation
 test1 = Sketchup.active_model.entities.add_instance ci_def, tr1
 ci_def2 = instance2.definition 
 tr2 = instance2.transformation
 test2 = Sketchup.active_model.entities.add_instance ci_def2, tr2
 result = test1.intersect(test2) # I can delete this later using something like an observer but would have to figure out how that works, also need to figure out how to make this work for more than 2 components and I need to figure out how to do it (multi)nested components.
 cnt = result.entities.count 
if  cnt > 0
 int=true
 result.material='red'
   # result.definition.entities.each {|ent|           ###When I run this in the plugin in console I get the following error "Done. Ruby says; uninitialized constant AS_RubyEditor;;RubyEditor;;Face"
   #   if ent.is_a? Sketchup;;Face
   #    Face.material = 'red' #Sketchup;;Color.new(255, 0, 0)
   #  end}
else
 int=false
end

#return int

If I run the code normally I get the following output "Done. Ruby says: red"
However the faces aren't red they just stay the original color.

glro

@bobvandevoort said:

..
If I run the code normally I get the following output "Done. Ruby says: red"
However the faces aren't red they just stay the original color.

they are red, actually... but inside. Faces a reversed

TIG

It's not Face.material = 'red'
it'd be ent.material = 'red'

pgarmyn

@TIG
In method def self.intersectALL()

(ens.length-1).times{|i|
         (ens.length-1).times{|j|
            next if j<=i # in place of  ; next if j==i
            if self.intersect?(ens[i], ens[j])
               ss.add(ens[i])
               ss.add(ens[j])
            end
         }

next if j<=i ( in place of next if j==i )
prevents double checking (slower) and double results.
If intersect?(ens[1], ens[2]) has been tested, then we don't have to test intersect?(ens[2], ens[1])

glro

@pgarmyn said:

@TIG
In method def self.intersectALL()

(ens.length-1).times{|i|
>          (ens.length-1).times{|j|
>             next if j<=i # in place of  ; next if j==i
>             if self.intersect?(ens[i], ens[j])
>                ss.add(ens[i])
>                ss.add(ens[j])
>             end
>          }

next if j<=i ( in place of next if j==i )
prevents double checking (slower) and double results.
If intersect?(ens[1], ens[2]) has been tested, then we don't have to test intersect?(ens[2], ens[1])

I don't know why, but neither TIG's version, nor yours, works on my computer

this is how i changed the code:

		model=Sketchup.active_model
		ss=model.selection
		ents=model.active_entities
		ss.clear
		gps=ents.grep(Sketchup;;Group)
		ins=ents.grep(Sketchup;;ComponentInstance)
		ens=gps+ins
		ens.uniq!
		ens.compact!
		for i in (0..ens.length-1)
			for j in ((i+1)..ens.length-1)
				if TIG.intersect?(ens[i], ens[j])
					ss.add(ens[i])
					ss.add(ens[j])
				end
			end
		end
        puts "Any intersecting groups/component-instances are highlighted..."

length-1 because it because i begins at 0...
and the i+1 to avoid comparing i to itself

is this version much slower than yours?

pgarmyn

@giro

		model=Sketchup.active_model
		ss=model.selection
		ents=model.active_entities
		ss.clear
		gps=ents.grep(Sketchup;;Group)
		ins=ents.grep(Sketchup;;ComponentInstance)
		ens=gps+ins
		ens.uniq!
		ens.compact!
		for i in (0..ens.length-2)  ############changed from length-1 to length-2
			for j in ((i+1)..ens.length-1)
				if TIG.intersect?(ens[i], ens[j])
					ss.add(ens[i])
					ss.add(ens[j])
				end
			end
		end
        puts "Any intersecting groups/component-instances are highlighted..."

I think, in this case, the last TIG.intersect?(ens[i], ens[j]) is with i=length-2 and j=length-1
Otherwise j = i+1 will become ens.length : for 5 elements (0 to 4) in ens, j will be 5.

glro

@pgarmyn said:

@glro

I think, in this case, the last TIG.intersect?(ens[i], ens[j]) is with i=length-2 and j=length-1
Otherwise j = i+1 will become ens.length : for 5 elements (0 to 4) in ens, j will be 5.

yes, i agree
it works in both cases, but your version should be faster

Bobvandevoort

@tig said:

It's not Face.material = 'red'
it'd be ent.material = 'red'

Thanks this solved it

Btw there's a way to do it with the intersect_with function and rule out most of the touching elements.
Any 3d volume needs at least 4 faces, so do a face count for ges and see if it equals 4 or more.
I know there probably some odd situations where it would still only be touching but then you could check if the faces form a solid if it doesn't form a solid it's a touch (I think this should be a correct way to implement this).

Let me know your thought about this method

(in any real 3d modeling you only need to find volumetric intersections and if you also want to find out of they are thouching we already have the method you previously described.

Everybody else thanks for the response and sorry for the delay on my side with responding, I have been away for 2 days.

pgarmyn

@bobvandevoort
To rule out most of the elements :
You can exclude elements based on boundingbox values :
Elements a and b won't intersect
If a.bounds.max.x < b.bounds.min.x
If a.bounds.min.x > b.bounds.max.x
If ..... 4 other tests with .y and .z

I'm not shure if this will speed up your code. I can imagen that those tests are also done by the (faster) intersect method of the API