R package for reading / writing 3D file (. PLY)

Duncan Murdoch-2 wrote:
On 11/12/2009 4:56 AM, kvarpun wrote:
Hi,

Is there an R package that reads and writes 3D images having the
extension
PLY (PLY images of Stanford University)?

Currently, I installed the package misc3d. This package displays these
images PLY, but it can neither read nor write PLY images.
This doesn't make sense.  How can it display PLY images if it can't read 
them?  Could you give an example?

Duncan Murdoch

Thank you to tell me the name of a package that will read and write such
images.

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Thank you for quick answer.
I have to inform you that the only available functions in the package misc3d
are:

contour3d                 Draw an Isosurface, a Three Dimension Contour Plot
  drawScene            Rendering of Triangular Mesh Surface Data
  image3d                Draw Points on a 3D Grid
  kde3d                    Compute a Three Dimension Kernel Density Estimate
  makeTriangles       Triangle Mesh Functions
  parametric3d          Draw a 3D Parametric Plot
  perspLighting          Lighting Functions
  phongLighting         Lighting Functions
  pointsTetrahedra     Create a Set of Tetrahetra Centered at Data Points
  scaleTriangles       Triangle Mesh Functions
  slices3d                 Interactive Image Slices of 3D or 4D Volume Data
  surfaceTriangles     Create a Triangle Mesh Representing a Surface
  teapot                    Utah Teapot
  translateTriangles   Triangle Mesh Functions
  updateTriangles      Triangle Mesh Functions

None of them does read/write a PLY file.

You will find below a simple code for drawing a 3D image. The displayed
image is stored in the package misc3d (not read from a file). 

library(misc3d)
data(teapot)

haveRGL <- suppressWarnings(require(rgl,quietly=TRUE))
ttri <- makeTriangles(teapot$vertices, teapot$edges, color = "red", color2 =
"green")

## draw the teapot
drawScene(ttri,screen=list(y=-30,x=40), scale = FALSE) 

str(teapot)
# > str(teapot)
# List of 2
# $ vertices: num [1:3, 1:1976] -3,00 1,65 0,00 -2,99 1,65 ...
# $ edges   : int [1:3, 1:3751] 1455 1469 1459 1449 1455 1459 1462 1449 1459
1469 ...

# My images (PLY images) have vertices and edges like the teapot image in
the example. If PLY images are read by R, I will be able to manipulate them.
Okay, I understand now.  Yes, R can display 3D images based on lines and 
polygons using the rgl package or scatterplot3d or grid graphics, but 
those have nothing to do with PLY files.  As far as I know there is no 
existing code to read or write a PLY file, but from the look of it, it's 
a simple format and it wouldn't be hard to write input/output routines. 
  The likely problems are:

  - it's an open ended format, with each application allowed to define 
its own record types.  If your files come from an application that did 
that you may have trouble working out what was intended and reading it in.

  - some of the recommended elements are not supported in rgl or other 
3D renderers in R.  In particular, polygons with more than 4 vertices 
need to be decomposed into triangles or quads, and rgl knows nothing 
about refraction index:  you'd probably need a ray-tracing renderer for 
that.

  - rgl scenes contain text, and as far as I can see, there's no way to 
include that in a standard PLY file, so you'd need to invent your own 
record type for it.  Text is always hard to describe graphically, so 
this wouldn't be easy.

Duncan Murdoch

R package for reading / writing 3D file (. PLY)

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