design

Both quad() and quad_texture() return ‘mesh3d’ objects that may be plotted directly with rgls plot3d(), shade3d(), persp3d(), wire3d(), or dot3d().

All coordinates are in x [0, 1] and y [0, 1] and default to “y-up” (begin at 0)
Quad indexes are counter-clockwise, as required by rgl (see material3d back argument).
ydown flips the orientation so that y coordinates begin at 1 and count down, and ensures that quad indexes are reversed and correctly counter-clockwise.

R functions using src/

break_mesh() - removes topology from mesh3d, by expanding every coordinate from vertex array
quad() generate mesh3d, a rectangular array of quads in the plane in 0,1
quad_texture() - extension of quad() to include image texture, all geometry and texture has identical x-y plane coordinates in 0,1

Rcpp package using quad.h

These are callable from R.

IntegerVector quad_index_cpp(IntegerVector nx, IntegerVector ny, LogicalVector ydown) 
NumericVector quad_vertex_cpp(IntegerVector nx, IntegerVector ny, LogicalVector ydown, LogicalVector zh) 
NumericVector quad_vertex_matrix_cpp(IntegerVector nx, IntegerVector ny, LogicalVector ydown, LogicalVector zh)

Headers

quad_ib and quad_vb both return flat vectors, quad_matrix_vb returns a matrix (with optionally z and h).

./inst/include/quad/quad.h namespace quad

IntegerVector quad_ib(IntegerVector nx, IntegerVector ny, LogicalVector ydown, LogicalVector zh);
NumericVector quad_vb(IntegerVector nx, IntegerVector ny, LogicalVector ydown, LogicalVector zh);
NumericVector quad_matrix_vb(IntegerVector nx, IntegerVector ny, LogicalVector ydown, LogicalVector zh);

- Design