1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
|
package draw
import (
"../structs"
"github.com/fogleman/gg"
"math"
)
// initializePlot generates a new plot and returns the plot context
func initializePlot() *gg.Context {
// Define the image size
const imageWidth = 8192
const imageHeight = 8192
// Initialize the new context
dc := gg.NewContext(imageWidth, imageHeight)
// Set the background black
dc.SetRGB(0, 0, 0)
dc.Clear()
// Invert the Y axis (positive values are on the top and right)
dc.InvertY()
// Set the coordinate midpoint to the middle of the image
dc.Translate(imageWidth/2, imageHeight/2)
return dc
}
// saveImages saves the given context to a png at the given path
func saveImage(dc *gg.Context, path string) {
dc.SavePNG(path)
}
// drawStar draws the given stars to the given context
func drawStar(dc *gg.Context, star structs.Star2D) {
// set radius of the star to 2
R := 2.0
// if the star has a greater mass than the default 5E4, it's radius is increased to 5
if star.M > 5E4 {
R = 5
}
// draw the star / point
dc.DrawPoint(star.C.X/50, star.C.Y/50, R)
dc.Fill()
dc.Stroke()
}
func drawVelocity(dc *gg.Context, star structs.Star2D) {
// scaling factor for a better view of the velocity difference
var scalingFactor float64 = 15
// Move the "cursor" to the start position of the vector
dc.MoveTo(star.C.X/50, star.C.Y/50)
// calculate the length of the vector
vecLength := star.V.GetLength()
// Use a sigmoid function to generate useful values for coloring the vectors according to their
// strength
var val = 1.0 / (1.0 + math.Exp(-vecLength*scalingFactor/2))
// Set the color to a blue / red
dc.SetRGB(val, 0, 1-val)
// calculate the direction vector
FUnit := (&star.V).Divide(vecLength)
// set end-position of the vector line
dc.LineTo(star.C.X/50+(FUnit.X*scalingFactor), star.C.Y/50+(FUnit.Y*scalingFactor))
// set line width
dc.SetLineWidth(3)
// And finally: DRAW (stroke) the vector
dc.Stroke()
}
// drawStars draws all the stars in the given slice to the given context
func drawStars(dc *gg.Context, slice []structs.Star2D) {
// draw all the velocity in the given slice
for _, star := range slice {
drawVelocity(dc, star)
}
dc.SetRGB(1, 1, 1)
// draw all the stars in the given slice
for _, star := range slice {
drawStar(dc, star)
}
}
// Slice draws the stars and the forces acting on them and saves the result to the given path
func Slice(slice []structs.Star2D, path string) {
// initialize the plot
dc := initializePlot()
// draw all the stars in the given slice
drawStars(dc, slice)
dc.SetRGB(1, 1, 1)
// drawing the 4 big stars as bigger white dots
//dc.DrawCircle(600, 600, 5)
//dc.DrawCircle(-600, 600, 5)
//dc.DrawCircle(-600, 0, 5)
//dc.DrawCircle(600, -600, 5)
dc.Fill()
// save the plot to the given path
saveImage(dc, path)
}
|
