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
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