tins2021/polygons.go

package tins2021

import (
	"image"

	"github.com/llgcode/draw2d/draw2dimg"
	"opslag.de/schobers/geom"
)

const TextureSize = 128

func CreateHeart() geom.PolygonF {
	var polygon geom.PolygonF
	const segments = 100
	for segment := 0; segment < 100; segment++ {
		t := 2 * geom.Pi * float64(segment) / segments
		st := geom.Sin(t)
		polygon.Points = append(polygon.Points, geom.PtF(
			16*st*st*st,
			13*geom.Cos(t)-5*geom.Cos(2*t)-2*geom.Cos(3*t)-geom.Cos(4*t)))
	}
	return polygon.Reverse().Mul(1. / 16)
}

func CreateHexagon() geom.PolygonF {
	var polygon geom.PolygonF
	pt := func(rotation float64) geom.PointF {
		a := .5*geom.Pi + 2*geom.Pi*rotation
		return geom.PtF(geom.Cos(a), geom.Sin(a))
	}
	const sides = 6
	for side := 0; side < 6; side++ {
		polygon.Points = append(polygon.Points,
			pt(float64(side)/float64(sides)),
		)
	}
	return polygon
}

func CreateStar(sides int) geom.PolygonF {
	var polygon geom.PolygonF
	pt := func(rotation float64) geom.PointF {
		a := .5*geom.Pi + 2*geom.Pi*rotation
		return geom.PtF(geom.Cos(a), geom.Sin(a))
	}
	for side := 0; side < sides; side++ {
		polygon.Points = append(polygon.Points,
			pt(float64(side)/float64(sides)),
			pt((float64(side)+0.5)/float64(sides)).Mul(.5),
		)
	}
	return polygon
}

func RenderPolygon2D(polygon geom.PolygonF, hexColor string) image.Image {
	im := image.NewRGBA(image.Rect(0, 0, TextureSize, TextureSize))
	color := mustHexColor(hexColor)
	gc := draw2dimg.NewGraphicContext(im)
	fillStrokeToGC(gc, color, polygon.Points...)
	return im
}

func RenderTriangles2D(triangles []geom.TriangleF, hexColor string) image.Image {
	im := image.NewRGBA(image.Rect(0, 0, TextureSize, TextureSize))
	color := mustHexColor(hexColor)
	gc := draw2dimg.NewGraphicContext(im)
	for _, triangle := range triangles {
		strokeToGC(gc, color, triangle.Points[:]...)
	}
	return im
}

func RenderTriangleSides2D(triangles []geom.TriangleF) image.Image {
	im := image.NewRGBA(image.Rect(0, 0, TextureSize, TextureSize))
	r, g, b := mustHexColor(`#FF0000`), mustHexColor(`#00FF00`), mustHexColor(`#0000FF`)
	gc := draw2dimg.NewGraphicContext(im)
	gc.SetLineWidth(2)
	for _, triangle := range triangles {
		inset := triangle.Inset(5)
		gc.SetStrokeColor(r)
		gc.MoveTo(inset.Points[0].XY())
		gc.LineTo(inset.Points[1].XY())
		gc.Stroke()
		gc.SetStrokeColor(g)
		gc.MoveTo(inset.Points[1].XY())
		gc.LineTo(inset.Points[2].XY())
		gc.Stroke()
		gc.SetStrokeColor(b)
		gc.MoveTo(inset.Points[2].XY())
		gc.LineTo(inset.Points[0].XY())
		gc.Stroke()
	}
	return im
}