Determine where 2 extruded lines intersect

[kenc]

If I have 2 walls(lines) crossing over or one of them is just touching the other, how do I determine at what point they intersect.

TIA

Ken

[denisT.MaxDoctor]

I'd love to help you, but you're on my blacklist. I don't appreciate it when someone claims “solutions” for themselves, even if they are their own. You have eight “solutions,” all marked by you. That's not how things should work. 
☝️

[kenc]

I'm sorry. I thought that is what I was supposed to do

[kenc]

Who marks it as a solution?

[kenc]

@denisT.MaxDoctor I just went through our previous threads and I do see what I did wrong.

In those I accepted solution. Also noticed 2 real old threads with marked accept solution by the moderator

[denisT.MaxDoctor]

are we talking about Bezie splines or just a simple Linear?

are we talking about 2D intersections? meaning projection 

[kenc]

@denisT.MaxDoctor I am talking about 3D linear walls. The point when one wall touches or passes through another wall.

[MartinBeh]

You don't mention what you want to do once you have the intersection, but 3ds Max has the "Section" shape which computes the intersection of a mesh with a plane - does that help?

[kenc]

@MartinBeh Where Line002 crosses Line001. I need to divide Line001 in two.

[MartinBeh]

So you want to cut one plane along the line of intersection of that plane with another?

You could use a Slice modifier for this. If you want, you could remote-control the modifier's gizmo with the gizmoControl script of mine.

Or maybe the Procutter compound would be a way to do that?

[kenc]

I better expand on what I need to do. I should have done this from the start.

I have a house full of walls. I have to check which wall intersects with what walls. I can do this with

intersects $Wall001 $Wall002.

When I find a wall that intersects another wall that wall needs to be split in two.

Here is an example

Wall005 and Wall006 intersect with Wall001. I need Wall005 to split Wall001 in two. As well as Wall006 to split it in two.

I am using MAX 2019

[denisT.MaxDoctor]

Typically, in any architectural project, “wall line” refers to a horizontal line (floor plan), not a vertical line. In this case, we can talk about the intersection in 2D (floor), or in 3D, assuming there is another vector making the wall plane “UP”.

If you use a vertical line for the wall, you need another vector to define the wall plane... where to get it?

[kenc]

@denisT.MaxDoctor I'm not following what you are getting at.

The walls are extruded lines and then collapsed to edit poly.

[denisT.MaxDoctor]

---

@kenc wrote:

@denisT.MaxDoctor I'm not following what you are getting at.

The walls are extruded lines and then collapsed to edit poly.

---

Walls are usually extruded vertically. In your original pipeline, they are extruded horizontally. Maybe it makes sense to modify the pipeline first?

[kenc]

@denisT.MaxDoctor  in both my screenshots above, the walls are extruded vertically

[denisT.MaxDoctor]

---

@kenc wrote:

@denisT.MaxDoctor  in both my screenshots above, the walls are extruded vertically

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According to this picture, the lines are vertical.

Well, uh. What do you need? Math, how do you calculate the intersecting point of two segments?

[denisT.MaxDoctor · Accepted solution]

fn segs_cross_point p11 p12 p21 p22 = 
(
	a = p12 - p11
	b = p22 - p21
	c = p21 - p11

	mag = cross a b
	len = (length mag) ^ 2

	p0 = p11 + a * (dot (cross c b) mag)/len
	p1 = p21 + b * (dot (cross c a) mag)/len

	(p0 + p1)/2
)

delete objects
--seed (timestamp())

p11 = point name:#p11 pos:(random -[100,100,0] [100,100,0]) cross:on wirecolor:green
p12 = point name:#p12 pos:(random -[100,100,0] [100,100,0]) cross:on wirecolor:green

p21 = point name:#p21 pos:(random -[100,100,0] [100,100,0]) cross:on wirecolor:yellow
p22 = point name:#p22 pos:(random -[100,100,0] [100,100,0]) cross:on wirecolor:yellow


v = segs_cross_point p11.pos p12.pos p21.pos p22.pos
cp = point name:#cross pos:v cross:on wirecolor:red

[kenc]

@denisT.MaxDoctor and how to break the wall at the intersection.

Wow, high school math. I was not expecting that.

I thought there would have been a built-in function to determine the point of intersection. Like intersects $Wall001 $Wall002. It determines if they intersect but no function to determine the point of intersection.

[MartinBeh]

What intersects really does is:

Returns true if the bounding boxes of the two specified nodes overlap, or false if they do not overlap

[kenc]

@MartinBeh What I'm saying is if script can determine an intersection occurring, then why not determine the point of intersection.