在MATLAB中加载stl文件并转换为3D数组 [英] Load stl file in matlab and convert to a 3D array
问题描述
我有一个stl文件,并已使用stlread函数将其加载到Matlab中.在这一点上,我有一组面和顶点.如何在3D二进制数组(如512x512x100数组)中转换这些面和顶点以获得二进制3D体积?
I have a stl file and I've loaded it in Matlab using stlread function. At this point I have a set of faces and vertices. How can I convert these faces and vertices in a 3D binary array like 512x512x100 array to obtain a binary 3D volume?
推荐答案
幸运的是.我最近正在使用STL文件,并且我编写了一些函数来做到这一点.
Ah lucky you. I am working with STL files recently and I coded some functions to do exactly this.
首先,请注意您会失去精度. STL文件以任意精度表示任意形状,并将其转换为体积会导致离散化和损失.
First, note that you lose precision. STL files represent arbitrary shapes with arbitrary precision and converting it into a volume results in discretization and losses.
也就是说,有一种非常简单的方法来知道某物体是否在闭合,连接的三角曲面的内部或外部,而不管其是否凸出:向无限和计数相交处投射射线与表面.如果是奇数,则为内部,如果是偶数,则为外部.
That said, there is a very easy method to know if something is inside or outside a closed, connected triangulated surface, regardless if its convex or not: Throw a ray to the infinite and count intersection with the surface. If odd, its inside, if even, outside.
您唯一需要的特殊代码是直线三角形相交,而MöllerTrumbore算法是最常用的代码之一.
The only special code you need is the line-triangle intersection, and the Möller Trumbore algorithm is one of the most common ones.
function in=inmesh(fv,points)
%INMESH tells you if a point is inside a closed,connected triangulated surface mesh
% Author: Ander Biguri
maxZ=max(fv.vertices(:,3));
counts=zeros(size(points,1),1);
for ii=1:size(points,1)
ray=[points(ii,:);points(ii,1:2) maxZ+1];
for jj=1:size(fv.faces,1)
v=fv.vertices(fv.faces(jj,:),:);
if all(v(:,3)<ray(1,3))
continue;
end
isin=mollerTrumbore(ray, fv.vertices(fv.faces(jj,:),:));
counts(ii)=counts(ii)+isin;
end
end
in=mod(counts,2);
end
在 FileExchange 中,进行了少量修改:>
From FileExchange, with small modifications:
function [flag, u, v, t] = mollerTrumbore (ray,tri)
% Ray/triangle intersection using the algorithm proposed by Moller and Trumbore (1997).
%
% IMPORTANT NOTE: Assumes infinite legth rays.
% Input:
% ray(1,:) : origin.
% d : direction.
% tri(1,:), tri(2,:), tri(3,:): vertices of the triangle.
% Output:
% flag: (0) Reject, (1) Intersect.
% u,v: barycentric coordinates.
% t: distance from the ray origin.
% Author:
% Jesus Mena
d=ray(2,:)-ray(1,:);
epsilon = 0.00001;
e1 = tri(2,:)-tri(1,:);
e2 = tri(3,:)-tri(1,:);
q = cross(d,e2);
a = dot(e1,q); % determinant of the matrix M
if (a>-epsilon && a<epsilon)
% the vector is parallel to the plane (the intersection is at infinity)
[flag, u, v, t] = deal(0,0,0,0);
return;
end
f = 1/a;
s = ray(1,:)-tri(1,:);
u = f*dot(s,q);
if (u<0.0)
% the intersection is outside of the triangle
[flag, u, v, t] = deal(0,0,0,0);
return;
end
r = cross(s,e1);
v = f*dot(d,r);
if (v<0.0 || u+v>1.0)
% the intersection is outside of the triangle
[flag, u, v, t] = deal(0,0,0,0);
return;
end
if nargout>3
t = f*dot(e2,r); % verified!
end
flag = 1;
return
end
只需生成您的观点:
yourboundaries=% get the range of your data from the STL file.
[x,y,z]=meshgrid(yourboundaries);
P=[x(:) y(:) z(:)];
in=inmesh(fv,P);
img=reshape(in,yourboundariesSize);
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