#### Archived

This topic is now archived and is closed to further replies.

# Intertection of a Plane and a Polygon

This topic is 6206 days old which is more than the 365 day threshold we allow for new replies. Please post a new topic.

## Recommended Posts

I''ve searched through the message boards but so far I haven''t found anything about how to compute the intersection of a polygon with a plane. I know how to find the intersection of a line and a plane but not for a polygon. I know that the intersection will be in the form of a line but I can''t seem to figure it out (I don''t have anymore that a grade 12 math.) I would appreciate any help on the subject. Thanks in advance.

##### Share on other sites
What you''re doing is a clipping problem. You''re clipping a polygon against a plane. Simple algorithm: go around all your points determining if they are ''in front'' or ''behind'' the plane. If the previous point tested was on the opposite side of the plane, you have to work out the intersection point (a simple ray/plane intersection). This will leave you with two sets of points - those on one side of the plane and those on the other.

##### Share on other sites

The intersection of a polygon and a plane is a line. How do I compute that line?

I know how to compute which side of a plane that a point is, but if the polygon needs to be clipped by the plane, where do I slit the polygon?

I''m looking for some sort of an equation or insight into figuring it out myself.

Again, Thanks.

##### Share on other sites
MagicScript: You said that you know how to find intersection of line and plane. Then the simplest way to find intersection of polygon and plane is to intersect the plane with polygons edge (lines). You have two edges intersecting the plane and get two points. These points are on the intersection line.

##### Share on other sites
Thank you, I''ll do that.

Could anyone tell me what kind of math this is? I was thinking Linear Algebra. Maybe I''ll be able to find some textbooks for future reference.

##### Share on other sites
It''s called Computational Geometry. If your looking for some references go to the comp.graphics.algorith FAQ. Check out Section 0.04 for the must-have books for graphics.

http://www.faqs.org/faqs/graphics/algorithms-faq/

1. 1
2. 2
Rutin
18
3. 3
4. 4
5. 5

• 14
• 12
• 9
• 12
• 37
• ### Forum Statistics

• Total Topics
631429
• Total Posts
3000033
×