// main creates a new scene with a camera and 3 vectors, renders the scene,
// draws the result to an image and encodes the image as PNG into a file.
// Optionally specify the filename.
func main() {
var filename = flag.String("file", "triangle.png", "Filename to store image")
flag.Parse()
cam := render.NewDefCam()
v1 := geom.NewVec4(-1, -1, -3)
v2 := geom.NewVec4(0, 1, -5)
v3 := geom.NewVec4(1, -1, -3)
t := cam.PerspTransf(500, 500)
w1 := t.Transf(v1)
w1.Norm()
w2 := t.Transf(v2)
w2.Norm()
w3 := t.Transf(v3)
w3.Norm()
x1 := tmath.Round(w1[0])
y1 := tmath.Round(w1[1])
x2 := tmath.Round(w2[0])
y2 := tmath.Round(w2[1])
x3 := tmath.Round(w3[0])
y3 := tmath.Round(w3[1])
img := image.NewImage(500, 500)
col := color.RGBA{255, 255, 0, 255}
img.DrawDot(x1, y1, col)
img.DrawDot(x2, y2, col)
img.DrawDot(x3, y3, col)
img.DrawLine(x1, y1, x2, y2, col)
img.DrawLine(x2, y2, x3, y3, col)
img.DrawLine(x3, y3, x1, y1, col)
file, err := os.Create(*filename)
if err != nil {
panic(err)
}
defer file.Close()
img.WritePng(file)
}
// Line draws a line between two points. It's 1 pixel thick.
func (w *Window) Line(v1, v2 *geom.Vec2, r, g, b byte) {
// Always draw from left to right (x1 <= x2)
if v1[0] > v2[0] {
v1, v2 = v2, v1
}
dx := v2[0] - v1[0]
dy := v2[1] - v1[1]
var steps int
if tmath.Absi(dx) > tmath.Absi(dy) {
steps = dx
} else {
steps = tmath.Absi(dy)
}
xinc := float64(dx) / float64(steps)
yinc := float64(dy) / float64(steps)
x := float64(v1[0])
y := float64(v1[1])
for s := 0; s <= steps; s++ {
w.Setxy(tmath.Round(x), tmath.Round(y), r, g, b)
x += xinc
y += yinc
}
}
// DrawLine draws a 1 pixel thick line between the (x1,y1) and (x2,y2) with the
// given color.
func (img *Image) DrawLine(x1, y1, x2, y2 int, c color.Color) {
r := img.Rgba
// Always draw from left to right (x1 <= x2)
if x1 > x2 {
x1, y1, x2, y2 = x2, y2, x1, y1
}
dx := x2 - x1
dy := y2 - y1
var steps int
if tmath.Absi(dx) > tmath.Absi(dy) {
steps = tmath.Absi(dx)
} else {
steps = tmath.Absi(dy)
}
xinc := float64(dx) / float64(steps)
yinc := float64(dy) / float64(steps)
x := float64(x1)
y := float64(y1)
for s := 0; s <= steps; s++ {
r.Set(tmath.Round(x), tmath.Round(y), c)
x += xinc
y += yinc
}
}
// Transf transforms a 3D triangle with the given transformation matrix and
// returns a 2D triangle.
func (t *Tri4) Transf(m *geom.Mat4) *Tri2 {
p1 := m.Transf(&t[0])
x1 := tmath.Round(p1[0] / p1[3])
y1 := tmath.Round(p1[1] / p1[3])
p2 := m.Transf(&t[1])
x2 := tmath.Round(p2[0] / p2[3])
y2 := tmath.Round(p2[1] / p2[3])
p3 := m.Transf(&t[2])
x3 := tmath.Round(p3[0] / p3[3])
y3 := tmath.Round(p3[1] / p3[3])
return NewTri2(x1, y1, x2, y2, x3, y3)
}