4

It is often need to draw triangular mesh using gnuplot.

Only way I currently see is to make "wireframe" using with lines option and double newlines between closed chains of lines (first and last point are the same) for each facet:

$wireframe <<EOD
 0  1 1 p1
 1 -1 1 p2
-1 -1 1 p3
 0  1 1 


 2  1 0 p4
 0  1 1 
 1 -1 1 
 2  1 0 


 0 -2 0 p5
 1 -1 1 
-1 -1 1 
 0 -2 0 


-2  1 0 p6
-1 -1 1 
 0  1 1 
-2  1 0 
EOD
splot '$wireframe' with lines notitle, '' with labels offset character 0, character 1 notitle

This is the 4 triangles: 1 at center (p1, p2, p3) and 3 are adjacent to its legs.

There is many duplication for some ways to define a mesh. Sometimes it is more appropriate way to define the mesh as a triangle strip or triangle fan.

Another issue is to fill the interior of the 3D triangles by some color. Currently I only can draw wireframe using different colors (from palette) for different chained lines. But they overlap.

Say, I want to draw icosahedron. It is closed solid, constrained by a triangle faces.

Tomilov Anatoliy
  • 15,657
  • 10
  • 64
  • 169

2 Answers2

4
set terminal wxt size 800,600

#set title "Graph Title"
#set xlabel "X"
#set ylabel "Y"
#set zlabel "Z"

# sets background color
set object 1 rectangle from screen -0.1,-0.1 to screen 1.1,1.1 fillcolor rgb "#ffffff" behind

# allows rendering of polygons with hidden line removal
set hidden3d back offset 0 trianglepattern 3 undefined 1 altdiagonal bentover

# displays borders 0x7F = 0b1111111
set border 0x7F linecolor rgb "#555555"

# displays the x, y and z axis
set xzeroaxis linewidth 0.5 linetype 1
set yzeroaxis linewidth 0.5 linetype 2
set zzeroaxis linewidth 0.5 linetype 3

# displays the x, y and z grid
set grid xtics linecolor rgb "#888888" linewidth 0.2 linetype 9
set grid ytics linecolor rgb "#888888" linewidth 0.2 linetype 9
set grid ztics linecolor rgb "#888888" linewidth 0.2 linetype 9

# moves the x, y grid to 0
set xyplane at 0

# makes the x, y, and z axis proportional
set view equal xyz

# sets the axis range
set xrange [-10:10]
set yrange [-10:10]
set zrange [-10:10]

# moves the key out of the graph
set key outside vertical bottom right

# hides the key
set key off

splot\
"ico.dat" title "ico" with lines linewidth 2.1 linecolor rgb "#88FF88"

ico.dat:

-1.381925 -4.253200 -2.236075
0.000000 0.000000 -5.000000

3.618000 -2.628600 -2.236075
3.618000 -2.628600 -2.236075


3.618000 -2.628600 -2.236075
0.000000 0.000000 -5.000000

3.618000 2.628600 -2.236075
3.618000 2.628600 -2.236075


-4.472125 0.000000 -2.236075
0.000000 0.000000 -5.000000

-1.381925 -4.253200 -2.236075
-1.381925 -4.253200 -2.236075


-1.381925 4.253200 -2.236075
0.000000 0.000000 -5.000000

-4.472125 0.000000 -2.236075
-4.472125 0.000000 -2.236075


3.618000 2.628600 -2.236075
0.000000 0.000000 -5.000000

-1.381925 4.253200 -2.236075
-1.381925 4.253200 -2.236075


3.618000 -2.628600 -2.236075
3.618000 2.628600 -2.236075

4.472125 0.000000 2.236075
4.472125 0.000000 2.236075


-1.381925 -4.253200 -2.236075
3.618000 -2.628600 -2.236075

1.381925 -4.253200 2.236075
1.381925 -4.253200 2.236075


-4.472125 0.000000 -2.236075
-1.381925 -4.253200 -2.236075

-3.618000 -2.628600 2.236075
-3.618000 -2.628600 2.236075


-1.381925 4.253200 -2.236075
-4.472125 0.000000 -2.236075

-3.618000 2.628600 2.236075
-3.618000 2.628600 2.236075


3.618000 2.628600 -2.236075
-1.381925 4.253200 -2.236075

1.381925 4.253200 2.236075
1.381925 4.253200 2.236075


4.472125 0.000000 2.236075
1.381925 -4.253200 2.236075

3.618000 -2.628600 -2.236075
3.618000 -2.628600 -2.236075


1.381925 -4.253200 2.236075
-3.618000 -2.628600 2.236075

-1.381925 -4.253200 -2.236075
-1.381925 -4.253200 -2.236075


-3.618000 -2.628600 2.236075
-3.618000 2.628600 2.236075

-4.472125 0.000000 -2.236075
-4.472125 0.000000 -2.236075


-3.618000 2.628600 2.236075
1.381925 4.253200 2.236075

-1.381925 4.253200 -2.236075
-1.381925 4.253200 -2.236075


1.381925 4.253200 2.236075
4.472125 0.000000 2.236075

3.618000 2.628600 -2.236075
3.618000 2.628600 -2.236075


1.381925 -4.253200 2.236075
4.472125 0.000000 2.236075

0.000000 0.000000 5.000000
0.000000 0.000000 5.000000


-3.618000 -2.628600 2.236075
1.381925 -4.253200 2.236075

0.000000 0.000000 5.000000
0.000000 0.000000 5.000000


-3.618000 2.628600 2.236075
-3.618000 -2.628600 2.236075

0.000000 0.000000 5.000000
0.000000 0.000000 5.000000


1.381925 4.253200 2.236075
-3.618000 2.628600 2.236075

0.000000 0.000000 5.000000
0.000000 0.000000 5.000000


4.472125 0.000000 2.236075
1.381925 4.253200 2.236075

0.000000 0.000000 5.000000
0.000000 0.000000 5.000000

Generated by blender and a python script:
https://github.com/lowlevel86/blender-to-gnuplot

user2376639
  • 66
  • 2
1

a workaround could be to write a gawk/Python script which would parse the definition of the facets and generate a Gnuplot script where the facets would be drawn manually as polygons:

set xr [0:1]
set yr [0:1]
set zr [0:1]

#generate the polygons
set object polygon from 0,0,0 to 1,0,0 to 1,1,0 to 0,1,0 to 0,0,0 fc rgb "cyan" fillstyle solid 1.0 border lt -1
set object polygon from 1,0,0 to 1,1,0 to 1,1,1 to 1,0,1 to 1,0,0 fc rgb "cyan" fillstyle solid 1.0 border lt -1

#do not plot anything
splot 1/0
ewcz
  • 12,819
  • 1
  • 25
  • 47