nr_tri_mesh: Draw multiple triangles from mesh data

In nara: Native Raster Image Tools

Draw multiple triangles from mesh data

Description

Mesh data is a similar format to the mesh3d class of data defined in the rgl package.

Usage

nr_tri_mesh(nr, vertices, indices, color, tris = "all", use_alpha = TRUE)

nr_tri_coords(nr, coords, color, tris = "all", use_alpha = TRUE)

Arguments

nr	native raster image
vertices	Wide matrix of vertex coordinates where the first two rows are x and y coordinates. Extra coordinates are ignored.
indices	3xN wide integer matrix of index information. Each column holds the 3 indices which indicate the column index of the triangle vertices defined in the vertices argument.
color	color specification. Single color or one color per tri
tris	Which triangles should be drawn? Valid options: 'all' (default), 'ccw', 'cw'. The options 'ccw' and 'cw' limit plotting to those triangles where the order of the vertices are defined in a counter-clockwise or clockwise manner respectively. Note: when considering orientation or triangles remember that the y-axis is defined vertically down the screen.
use_alpha	Use alpha channel when drawing? Logical. Default: TRUE
coords	Wide numeric matrix of direct coordinate data for each triangle where the first two rows are x and y coordinates (extra rows are ignored) Each group of 3 columns defines the (x,y) coordinates for one triangle.

Value

Invisibly return the supplied native raster image which was been modified in-place

See Also

Other drawing functions: nr_circle(), nr_polygon(), nr_polyline(), nr_rect()

Examples

#' Using direct coordinates
set.seed(1)
w <- 100
h <-  80
nr <- nr_new(w, h)

n_tri <- 10
xs <- runif(n_tri * 3, 0, w - 1)
ys <- runif(n_tri * 3, 0, h - 1)
coords <- rbind(xs, ys)
cols <- rainbow(n_tri)

nr_tri_coords(nr, coords, cols, tris = 'all')
plot(nr)

# Using a standard mesh structure
# i.e. a matrix of vertices, and a matrix of indices 
nr <- nr_new(w, h)

# Matrix of coordinates
xs <- rep(seq(0, w - 1, length.out = 10), 10)
ys <- rep(seq(0, h - 1, length.out = 10), each = 10)
vertices <- rbind(xs, ys)
nr_point(nr, xs, ys)

plot(nr)

# Matrix of indices indicating which vertices make up each triangle
indices <- matrix(sample(length(xs), 3 * n_tri), nrow = 3) 

nr_tri_mesh(nr, vertices, indices, cols, tris = 'all')
plot(nr)

nara documentation built on May 28, 2026, 5:07 p.m.