RGL plot : lighting problem when triangle3d and persp3d are used in the same plot

Dear all,

I have tried to plot a triangular matrix with the function persp3d(rgl).

for example

z=rbind(c(1,NA,NA,NA),c(5,3,NA,NA),c(4,2,9,NA),c(8,6,5,11))
x=1:4
y=1:4
persp3d(x,y,z,color="gray")

The two extreme points are not plotted (value=1 and value=10). It seems
because the half of the matrix have 'NA'  and perp3d need planar
quadrilateral face. So I decided to use the function triangle3d to
integrate these points into the scene.

So, for the first point I did :

triangles3d(x=c(1,2,2),y=c(1,1,2),z=c(1,5,3)) and it worked

But a problem remains because the light movment on this triangle looks
independant and I did not find how to solve this issue.

How can I prefectly integrate this triangle into the scene?

thanks for the reply

I am sorry but I do not have any skills in C++

Nevertheless, I found a solution to my problem... By using another package
  "misc3d" and more precisely the association of the two
functions drawScene.rgl and surfaceTriangles

drawScene.rgl(surfaceTriangles(x,y,z,color="gray",smooth=1))

The idea behind this trick is to transform the matrix in triangle surfaces
before to plot them.

I hope this could help someone else

cheers



2012/8/27 Duncan Murdoch <murdoch.duncan at gmail.com>

On 27/08/2012 1:47 PM, Stephane Chantepie wrote:

Dear all,

I have tried to plot a triangular matrix with the function persp3d(rgl).

for example

z=rbind(c(1,NA,NA,NA),c(5,3,**NA,NA),c(4,2,9,NA),c(8,6,5,11)**)
x=1:4
y=1:4
persp3d(x,y,z,color="gray")

The two extreme points are not plotted (value=1 and value=10). It seems
because the half of the matrix have 'NA'  and perp3d need planar
quadrilateral face. So I decided to use the function triangle3d to
integrate these points into the scene.

So, for the first point I did :

triangles3d(x=c(1,2,2),y=c(1,**1,2),z=c(1,5,3)) and it worked

But a problem remains because the light movment on this triangle looks
independant and I did not find how to solve this issue.

How can I prefectly integrate this triangle into the scene?

You need to set the normals at the vertices that are shared with the
persp3d vertices.  rgl internally averages the normals to the pieces making
up each facet; you don't have enough access to the internals to do that.
 (You'd want to change the normal on the surface, as well, because your
triangles should participate in the averaging.)

But you could set the normals to the new triangle to match the normal to
the one it joins to, and get something that looks sort of okay.  It's not
going to be a simple calculation:  you need to figure out the coordinates
of the edges joining at those vertices, take a cross product, and use that.
 See ?rgl.primitive for how to send the normals to points3d; I think the
normals need to be length 1, but that may be forced internally.

If you were really ambitious, you could take a look at the C++ code that
draws the surface, and contribute code to smooth the edge properly; I think
it would be an improvement over the current behaviour, but it is tedious to
write.

Duncan Murdoch