Re: complex interscetions
- Posted by Andrew Gainey <amgainey at CUSTOM.NET> Apr 04, 1999
- 477 views
------=_NextPart_000_001A_01BE7E77.A61BCB80 charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable does anyone know a formula for line intersections through polygons. = I can do a 2d line intersection and a 3d line intersection, but this is = hurting my head. Any info would be helpful. reddager at animalis.com=20 I believe that if you have an equation for each line of a polygon(you = don't even need endpoints for this part) then you can figure out for = each line which direction is inside the polygon and which side is out by = using the > or < symbols. I remember in simple graphing in algebra I = class, we would have three equations. All of these (2D) had a > or < = instead of an =3D. Example: Graph the following: y < 1/2x + 2 y < -3x + 4 y > -1x - 1 The area in the middle is all that can possibly exist using those three = equations. I assume that this would be the same with 3 dimensional = equations. I'm not sure exactly how to do this, but I think it's = possible to use this to figure out if a 3d line intersects a 3d polygon = made with this method. I've thought about this already a little, and I = might more later. Hope this helps. ------=_NextPart_000_001A_01BE7E77.A61BCB80 charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable <!DOCTYPE HTML PUBLIC "-//W3C//DTD W3 HTML//EN"> <HTML> <HEAD> <META content=3Dtext/html;charset=3Diso-8859-1 = http-equiv=3DContent-Type> <META content=3D'"MSHTML 4.72.3110.7"' name=3DGENERATOR> </HEAD> <BODY bgColor=3D#ffffff> <DIV> does anyone know a formula for line = intersections=20 through polygons. I can do a 2d line intersection and a 3d line = intersection,=20 but this is hurting my head. Any info would be helpful.<BR><A=20 href=3D"mailto:reddager at animalis.com">reddager at animalis.com</A> = <BR></DIV> <DIV> </DIV> <DIV>I believe that if you have an equation for each line of a = polygon(you don't=20 even need endpoints for this part) then you can figure out for each line = which=20 direction is inside the polygon and which side is out by using the > = or <=20 symbols. I remember in simple <FONT size=3D3>graphing in algebra I = class, we=20 would have three equations. All of these (2D) had a > or < = instead=20 of an =3D.</FONT></DIV> <DIV><FONT size=3D3></FONT> </DIV> <DIV><FONT color=3D#000000><FONT size=3D3>Example:</FONT></FONT></DIV> <DIV><FONT color=3D#000000><FONT size=3D3></FONT></FONT><FONT = size=3D3></FONT>Graph=20 the following:</DIV> <DIV>y < 1/2x + 2</DIV> <DIV>y < -3x + 4</DIV> <DIV>y > -1x - 1</DIV> <DIV> </DIV> <DIV>The area in the middle is all that can possibly exist using those = three=20 equations. I assume that this would be the same with 3 dimensional = equations. I'm not sure exactly how to do this, but I think it's = possible=20 to use this to figure out if a 3d line intersects a 3d polygon made with = this=20 method. I've thought about this already a little, and I might more = later. Hope this helps.</DIV> ------=_NextPart_000_001A_01BE7E77.A61BCB80--