NF: function to generate planar surface

misc/surfing_generate_planar_surface.m

@@ -0,0 +1,98 @@
+function [vertices,faces]=surfing_generate_planar_surface(nx, ny, origin, x1, y1)
+% generate a surface in the shape of a plane
+%
+% [vertices,faces]=surfing_generate_planar_surface(nx, ny, origin, x1, y1)
+%
+% Inputs:
+%   nx          number of vertices in first dimension
+%   ny          number of vertices in second dimension
+%   origin      (optional) 1x3 vector with coordinates of origin. 
+%               Default: [0,0,0]
+%   x1          (optional) 1x3 vector with coordinates of second vertex
+%               (the origin being the first) in the first dimension. 
+%               Default: [1,0,0]
+%   y1          (optional) 1x3 vector with coordinates of second vertex
+%               (the origin being the first) in the second dimension
+%               Default: [0,1,0]
+%
+% Output:
+%   vertices    Px3 coordinates, with P = nx * ny
+%   faces       Qx3 faces, with Q=2*(nx-1)*(ny-1)
+%
+% Example:
+%     % generate a surface 
+%     [v,f]=surfing_generate_planar_surface(5,2,[0,0,0],[1,0,0],[0,1,0])
+%     > v =
+%     > 
+%     >      0     0     0
+%     >      0     1     0
+%     >      1     0     0
+%     >      1     1     0
+%     >      2     0     0
+%     >      2     1     0
+%     >      3     0     0
+%     >      3     1     0
+%     >      4     0     0
+%     >      4     1     0
+%     > 
+%     > 
+%     > f =
+%     > 
+%     >      1     2     3
+%     >      4     3     2
+%     >      3     4     5
+%     >      6     5     4
+%     >      5     6     7
+%     >      8     7     6
+%     >      7     8     9
+%     >     10     9     8
+%
+% Notes:
+%   - this function generates a surface consisting of rectangles, with
+%     three corners of the first rectangle being the origin, x1 and y1.
+%     Each rectangle consists of two triangles
+%
+% NNO Sep 2015
+
+if nargin<3
+    origin=[0,0,0];
+end
+
+if nargin<4
+    x1=[1,0,0];
+end
+
+if nargin<5
+    y1=[0,1,0];
+end
+
+
+cellfun(@ensure_is_three_vec,{origin,x1,y1});
+
+vertices=zeros(nx*ny,3);
+faces=zeros(2*(nx-1)*(ny-1),3);
+
+for i=1:nx
+    for j=1:ny
+        vpos=(i-1)*ny+j;
+        vertices(vpos,:)=origin+(i-1)*x1+(j-1)*y1;
+        if i<nx && j<ny
+            p=vpos;
+            q=vpos+1;
+            r=vpos+ny;
+            s=vpos+ny+1;
+
+            fpos=((i-1)*(ny-1)+j)*2-1;
+            faces(fpos,:)=[p,q,r];
+            faces(fpos+1,:)=[s,r,q];
+        end
+    end
+end
+
+function ensure_is_three_vec(x)
+    if ~(isnumeric(x) && ...
+            numel(x)==3 && ...
+            numel(size(x))==2)
+        error('vectors must have three numeric elements');
+    end
+