REQ: Checking if components (solids) 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

glro

@pgarmyn said:

@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.

i tried to run this code in sketchup 15 64 bits, thinking it could run faster than is sketchup 8

All the contrary

it is much slower in sketchup 15 64 bits... (about 10 times...)

i am very disapointed

am i the only one to experience that?

Bobvandevoort

This is my version of the srcipt for now that seems to work for all non nested component instances

module Bob

# Huge parts of this code were written by TIG this is a sligthly modified version

	def self.intersectBob?(e1=nil, e2=nil)
	
		mod = Sketchup.active_model # Open model
		ent = mod.entities # All entities in model
		instance1 = e1 #sel[0]
		instance2 = e2 #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) 
		cnt = result.entities.count 
		if  cnt > 0
			int=true
			result.definition.entities.each {|ent|
			if ent.is_a? Sketchup;;Face
				ent.material = 'red' #Sketchup;;Color.new(255, 0, 0)
			end}
		else
		int=false
		end
		
	return int
	end 
	
	#def self.del()	#does not work like this typing Bob.del into the ruby console, meaning result has to be changed from local to global variable but I don't know how yet
	#result.erase!	
	#end	

	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).times{|i|
			(ens.length).times{|j|
				next if j<=i
				if self.intersectBob?(ens[i], ens[j])
					ss.add(ens[i])
					ss.add(ens[j])
				end
			}
		}
		puts "Any intersecting component-instances are highlighted..."
	end
end

In this script I still need to fix the deleting function which later will have to be added to an observer class so as soon as another is clicked (or a button is pressed) the resulting intersection is deleted.

The more important function that still has to be added is that it does the check for all the nested components (and possibly groups).

@giro
I only have the 32 bits version so can't say