trans3d {grDevices} | R Documentation |

## 3D to 2D Transformation for Perspective Plots

### Description

Projection of 3-dimensional to 2-dimensional points using a 4x4
viewing transformation matrix. Mainly for adding to
perspective plots such as `persp`

.

### Usage

```
trans3d(x, y, z, pmat, continuous = FALSE, verbose = TRUE)
```

### Arguments

`x` , `y` , `z` |
numeric vectors of equal length, specifying points in 3D space. |

`pmat` |
a |

`continuous` |
logical flag specifying if the transformation should
check if the transformed points are continuous in the sense that they
do not jump over |

`verbose` |
only for |

### Value

a list with two components

`x` , `y` |
the projected 2d coordinates of the 3d input |

### See Also

### Examples

```
## See help(persp) {after attaching the 'graphics' package}
## -----------
## Example for 'continuous = TRUE' (vs default):
require(graphics)
x <- -10:10/10 # [-1, 1]
y <- -16:16/16 # [-1, 1] ==> z = fxy := outer(x,y) is also in [-1,1]
p <- persp(x, y, fxy <- outer(x,y), phi = 20, theta = 15, r = 3, ltheta = -75,
shade = 0.8, col = "green3", ticktype = "detailed")
## 5 axis-parallel auxiliary lines in x-y and y-z planes :
lines(trans3d(-.5 , y=-1:1, z=min(fxy), pmat=p), lty=2)
lines(trans3d( 0 , y=-1:1, z=min(fxy), pmat=p), lty=2)
lines(trans3d(-1:1, y= -.7, z=min(fxy), pmat=p), lty=2)
lines(trans3d( -1, y= -.7, z=c(-1,1) , pmat=p), lty=2)
lines(trans3d( -1, y=-1:1, z= -.5 , pmat=p), lty=2)
## 2 pillars to carry the horizontals below:
lines(trans3d(-.5 , y= -.7, z=c(-1,-.5), pmat=p), lwd=1.5, col="gray10")
lines(trans3d( 0 , y= -.7, z=c(-1,-.5), pmat=p), lwd=1.5, col="gray10")
## now some "horizontal rays" (going from center to very left or very right):
doHor <- function(x1, x2, z, CNT=FALSE, ...)
lines(trans3d(x=seq(x1, x2, by=0.5), y= -0.7, z = z, pmat = p, continuous = CNT),
lwd = 3, type="b", xpd=NA, ...)
doHor(-10, 0, z = -0.5, col = 2) # x in [-10, 0] -- to the very left : fine
doHor(-.5, 2, z = -0.52,col = 4) # x in [-0.5, 2] only {to the right} --> all fine
## but now, x in [-0.5, 20] -- "too far" ==> "wrap around" problem (without 'continuous=TRUE'):
doHor(-.5, 20, z = -0.58, col = "steelblue", lty=2)
## but it is fixed with continuous = CNT = TRUE:
doHor(-.5, 20, z = -0.55, CNT=TRUE, col = "skyblue")
```

*grDevices*version 4.4.0 Index]