# polyLineIntersect

Below is a demonstration of the features of the `polyLineIntersect` function

## Contents

```
clear; close all; clc;
```

## Syntax

`[Vn]=polyLineIntersect(V,n_cut,cutLevel,isClosed);`

## Description

Computes the intersection points between a polygon defined by the vertex array V and a line defined the the normal vector n_cut and the cutLevel. If isClosed==1 (True) then the curve is assumed to be closed (additional line element from start to end is included.

PLOT SETTINGS

fontSize=15; lineWidth=2; markerSize1=50; markerSize2=35;

## Examples

## Example 1: Computing intersections for a non-closed curve

n=25; t=linspace(0,2*pi,n)'; V_now=[t cos(t) zeros(size(t))]; n_cut=vecnormalize([0 1 0]); isClosed=0; numCutLevels=25; cutLevel=linspace(-2,2,numCutLevels)'; cFigure; hold on; plotV(V_now,'b.-','MarkerSize',markerSize1,'LineWidth',lineWidth); axis tight; axis equal; set(gca,'FontSize',fontSize); drawnow; for q=1:1:numel(cutLevel) [Vn]=polyLineIntersect(V_now,n_cut,cutLevel(q),isClosed); logicIntersect = any(~isnan(Vn),2); if any(logicIntersect) Vn_intersect = Vn(logicIntersect,:); plotV(Vn_intersect,'r.-','MarkerSize',markerSize2,'LineWidth',lineWidth); end end

## Example 2: Computing intersections for a closed curve

n=25; t=linspace(0,2*pi,n+1)'; t=t(1:end-1); V_now=[cos(t) sin(t) zeros(size(t))]; n_cut=vecnormalize([1 1 0]); isClosed=1; numCutLevels=25; cutLevel=linspace(max(V_now(:,2)),min(V_now(:,2)),numCutLevels)'; cFigure; hold on; plotV(V_now,'b.-','MarkerSize',markerSize1,'LineWidth',lineWidth); axis tight; axis equal; set(gca,'FontSize',fontSize); drawnow; for q=1:1:numel(cutLevel) [Vn]=polyLineIntersect(V_now,n_cut,cutLevel(q),isClosed); logicIntersect = any(~isnan(Vn),2); if any(logicIntersect) Vn_intersect = Vn(logicIntersect,:); plotV(Vn_intersect,'r.-','MarkerSize',markerSize2,'LineWidth',lineWidth); end end

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*Kevin Mattheus Moerman*, [email protected]

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License: https://github.com/gibbonCode/GIBBON/blob/master/LICENSE

GIBBON: The Geometry and Image-based Bioengineering add-On. A toolbox for image segmentation, image-based modeling, meshing, and finite element analysis.

Copyright (C) 2006-2023 Kevin Mattheus Moerman and the GIBBON contributors

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