Colors, shading, lighting.

Description

jet.col generates the matlab-type colors.

jet2.col is similar but lacks the deep blue colors

gg.col and gg2.col generate gg-plot-like colors.

ramp.col creates color schemes by interpolation.

alpha.col creates transparent colors.

Usage

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jet.col (n = 100, alpha = 1)

jet2.col (n = 100, alpha = 1)

gg.col (n = 100, alpha = 1)

gg2.col (n = 100, alpha = 1)

ramp.col (col = c("grey", "black"), n = 100, alpha = 1)

alpha.col (col = "grey", alpha = 0.5)

Arguments

n

Number of colors to generate.

alpha

Value in the range [0, 1] for alpha transparency channel (0 means transparent and 1 means opaque). Transparency defined in the color palette is overruled when lighting or shading is switched on. To combine transparency with lighting or shading, pass argument alpha to the plotting functions directly.

col

Colors to interpolate, change.

Details

In addition to the color functions described here, colors can also be adapted by shading and lighting, or made transparent. Shading will be overruled if lighting is not FALSE.

To make colors transparent, use argument alpha, with a value inbetween 0 and 1.

To switch on shading, the argument shade should be given a value inbetween 0 and 1.

To switch on lighting, the argument lighting should be either set to TRUE (in which case default settings will be used) or should be a list with specifications of one of the following: ambient, diffuse, specular, exponent, sr and alpha.

The defaults are: ambient = 0.3, diffuse = 0.6, specular = 1., exponent = 20, sr = 0, alpha = 1

Lighting is defined as the sum of ambient, diffuse and specular light. If N is the normal vector on the facets (3-values, x-, y-, z direction) and I is the light vector, then col = (ambient + Id + sr * Is) * col + (1 - sr) * Is, where Is = specular * abs(Light) ^ exponent, Id = diffuse * Light and Light = sum(N*I).

The lighting algorithm is very simple, i.e. it is flat shading, no interpolation.

Toggling on lighting or shading also requires the input of the angles of the light source, as ltheta and lphi, whose defaults are: ltheta = -135, lphi = 0. This usually works well for shading, but may not be optimal for lighting.

Value

A list with colors.

Author(s)

Karline Soetaert <karline.soetaert@nioz.nl>

References

The gg-plot type of colors gg.plot is a color-blind friendly palette from http://wiki.stdout.org/rcookbook/Graphs.

See Also

colorRamp and colorRampPalette for comparable (and more elaborate) R-functions.

Examples

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# save plotting parameters
 pm <- par("mfrow")
 pmar <- par("mar")

## =======================================================================
## Transparency and various color schemes
## =======================================================================

 par(mfrow = c(3, 3))
 for (alph in c(0.25, 0.75))
   image2D(volcano, alpha = alph, 
         main = paste("jet.col, alpha = ", alph))  
 image2D(volcano, main = "jet.col")
 image2D(volcano, col = jet2.col(100), main = "jet2.col")
 image2D(volcano, col = gg.col(100), main = "gg.col")
 image2D(volcano, col = gg2.col(100), main = "gg2.col")
 image2D(volcano, col = rainbow(100), main = "rainbow")
 image2D(volcano, col = terrain.colors(100), main = "terrain.colors")
 image2D(volcano, col = ramp.col(c("blue", "yellow", "green", "red")),
       main = "ramp.col")  

## =======================================================================
## Shading, lighting -  one color
## =======================================================================

# create grid matrices
 X      <- seq(0, pi, length.out = 50)
 Y      <- seq(0, 2*pi, length.out = 50)
 M      <- mesh(X, Y)
 phi    <- M$x
 theta  <- M$y

# x, y and z grids
 x <- sin(phi) * cos(theta)
 y <- cos(phi)
 z <- sin(phi) * sin(theta)

# these are the defaults
 p <- list(ambient = 0.3, diffuse = 0.6, specular = 1.,
           exponent = 20, sr = 0, alpha = 1)

 par(mfrow = c(3, 3), mar = c(0, 0, 0, 0))
 Col <- "red"

 surf3D(x, y, z, box = FALSE, col = Col, shade = 0.9)
 surf3D(x, y, z, box = FALSE, col = Col, lighting = TRUE)  
 surf3D(x, y, z, box = FALSE, col = Col, lighting = list(ambient = 0))
 surf3D(x, y, z, box = FALSE, col = Col, lighting = list(diffuse = 0))
 surf3D(x, y, z, box = FALSE, col = Col, lighting = list(diffuse = 1))
 surf3D(x, y, z, box = FALSE, col = Col, lighting = list(specular = 0))
 surf3D(x, y, z, box = FALSE, col = Col, lighting = list(exponent = 5))
 surf3D(x, y, z, box = FALSE, col = Col, lighting = list(exponent = 50))
 surf3D(x, y, z, box = FALSE, col = Col, lighting = list(sr = 1)) 

## =======================================================================
## Shading, lighting with default colors
## =======================================================================

 x <- seq(-pi, pi, len = 100)
 y <- seq(-pi, pi, len = 100)
 grid <- mesh(x, y)

 z    <- with(grid, cos(x) * sin(y))
 cv   <- with(grid, -cos(y) * sin(x))

# lphi = 180, ltheta = -130  - good for shade
# lphi = 90, ltheta = 0  - good for lighting

 par(mfrow = c(2, 2))
 persp3D(z = z, x = x, y = y, colvar = cv, zlim = c(-3, 3), colkey = FALSE)
 persp3D(z = z, x = x, y = y, colvar = cv, zlim = c(-3, 3), 
       lighting = TRUE, colkey = FALSE)
 persp3D(z = z, x = x, y = y, colvar = cv, zlim = c(-3, 3), 
       shade = 0.25, colkey = FALSE)
 persp3D(z = z, x = x, y = y, colvar = cv, zlim = c(-3, 3), 
       lighting = TRUE, lphi = 90, ltheta = 0, colkey = FALSE)

## =======================================================================
## transparency of a vector of colors
## =======================================================================

 par(mfrow = c(1, 1))
 x <- runif(19)
 y <- runif(19)
 z <- runif(19)
# split into 5 sections (polygons) 
 ii <- seq(4, 19, by = 4)
 x[ii] <- y[ii] <- z[ii] <- NA
  
 polygon3D(x, y, z, border = "black", lwd = 2, 
   col = alpha.col(c("red", "lightblue", "yellow", "green", "black"), 
                  alpha = 0.4))

# the same, now passing alpha as an argument to polygon3D:
## Not run: 
 polygon3D(x, y, z, border = "black", lwd = 2, 
   col = c("red", "lightblue", "yellow", "green", "black"), 
                  alpha = 0.4)

## End(Not run)
# reset plotting parameters
 par(mfrow = pm)
 par(mar = pmar)