primitives: Add primitive shape

In rgl: 3D Visualization Using OpenGL

Add primitive shape

Description

Adds a shape node to the current scene.

Usage

points3d(x, y = NULL, z = NULL,  ...)
lines3d(x, y = NULL, z = NULL,  ...)
segments3d(x, y = NULL, z = NULL, ...)
triangles3d(x, y = NULL, z = NULL, ...)
quads3d(x, y = NULL, z = NULL, ...)

Arguments

x, y, z	coordinates. Any reasonable way of defining the coordinates is acceptable. See the function xyz.coords for details.
...	Material properties (see material3d), normals, texcoords or indices; see details below.

Details

The functions points3d, lines3d, segments3d, triangles3d and quads3d add points, joined lines, line segments, filled triangles or quadrilaterals to the plots. They correspond to the OpenGL types GL_POINTS, GL_LINE_STRIP, GL_LINES, GL_TRIANGLES and GL_QUADS respectively.

Points are taken in pairs by segments3d, triplets as the vertices of the triangles, and quadruplets for the quadrilaterals. Colors are applied vertex by vertex; if different at each end of a line segment, or each vertex of a polygon, the colors are blended over the extent of the object. Polygons must be non-degenerate and quadrilaterals must be entirely in one plane and convex, or the results are undefined.

The appearance of the new objects are defined by the material properties. See material3d for details.

For triangles and quads, the normals at each vertex may be specified using normals. These may be given in any way that would be acceptable as a single argument to xyz.coords. These need not match the actual normals to the polygon: curved surfaces can be simulated by using other choices of normals.

Texture coordinates may also be specified. These may be given in any way that would be acceptable as a single argument to xy.coords, and are interpreted in terms of the bitmap specified as the material texture, with (0, 0) at the lower left, (1, 1) at the upper right. The texture is used to modulate the color of the polygon.

All of these functions support an argument called indices, which allows vertices (and other attributes) to be re-used, as they are in objects created by mesh3d and related functions. This is intended to be used on smooth surfaces, where each shared vertex has just one value for normals, colors and texture coordinates.

For shapes with flat-looking faces (e.g. polyhedra like cube3d), the vertices must be duplicated to be rendered properly.

Value

Each function returns the integer object ID of the shape that was added to the scene. These can be passed to pop3d to remove the object from the scene.

Author(s)

Ming Chen and Duncan Murdoch

Examples

# Show 12 random vertices in various ways. 

M <- matrix(rnorm(36), 3, 12, dimnames = list(c('x', 'y', 'z'), 
                                       rep(LETTERS[1:4], 3)))

# Force 4-tuples to be convex in planes so that quads3d works.

for (i in c(1, 5, 9)) {
    quad <- as.data.frame(M[, i + 0:3])
    coeffs <- runif(2, 0, 3)
    if (mean(coeffs) < 1) coeffs <- coeffs + 1 - mean(coeffs)
    quad$C <- with(quad, coeffs[1]*(B - A) + coeffs[2]*(D - A) + A)
    M[, i + 0:3] <- as.matrix(quad)
}

open3d()

# Rows of M are x, y, z coords; transpose to plot

M <- t(M)
shift <- matrix(c(-3, 3, 0), 12, 3, byrow = TRUE)

points3d(M)
lines3d(M + shift)
segments3d(M + 2*shift)
triangles3d(M + 3*shift, col = 'red')
quads3d(M + 4*shift, col = 'green')  
text3d(M + 5*shift, texts = 1:12)

# Add labels

shift <- outer(0:5, shift[1, ])
shift[, 1] <- shift[, 1] + 3
text3d(shift, 
       texts = c('points3d', 'lines3d', 'segments3d',
         'triangles3d', 'quads3d', 'text3d'),
       adj = 0)
 rgl.bringtotop()

rgl documentation built on Oct. 28, 2024, 5:07 p.m.