objects/box.go

package objects

import (
	"github.com/deadsy/sdfx/sdf"
	"math"
)

type BoxParams struct {
	Size           sdf.V3  // internal box size
	Wall           float64 // wall thickness
	BottomTopRatio float64 // ratio between the height of the top and the bottom
	CornerRadius   float64 // radius of rounded corners
	Taper          float64 // angle of split
	ClosingHeight  float64 // height of the closing
	Margin		   float64 // Margin for closing
	Text           string
}

func Box3D(k *BoxParams) (top sdf.SDF3, bottom sdf.SDF3, err error) {
	top, err = TopBox3D(k)
	bottom, err = TopBox3D(k)
	if err != nil {
		return
	}
	return
}

func baseBox3D(k *BoxParams) (sdf.SDF3, error) {
	box, err := sdf.Box3D(k.Size.AddScalar(k.Wall*2), k.CornerRadius)
	if err != nil {
		return nil, err
	}
	return box, nil
}

func TopBox3D(k *BoxParams) (top sdf.SDF3, err error) {
	box, err := baseBox3D(k)
	if err != nil {
		return
	}
	a := sdf.V3{X: 0, Y: 0, Z: 0.5 - k.BottomTopRatio}.Mul(k.Size).Add(sdf.V3{X: 0, Y: 0, Z: k.ClosingHeight / 2})
	n := sdf.V3{X: 0, Y: 0, Z: 1}
	top = sdf.Cut3D(box, a, n)
	closing, err := InnerClosing(k)
	if err != nil {
		return
	}
	top = sdf.Union3D(top,closing)
	return
}

func BottomBox3D(k *BoxParams) (bottom sdf.SDF3, err error) {
	box, err := baseBox3D(k)
	if err != nil {
		return
	}
	a := sdf.V3{X: 0, Y: 0, Z: 0.5 - k.BottomTopRatio}.Mul(k.Size).Add(sdf.V3{X: 0, Y: 0, Z: k.ClosingHeight / 2})
	n := sdf.V3{X: 0, Y: 0, Z: -1}
	bottom = sdf.Cut3D(box, a, n)
	closing, err := InnerClosing(k)
	scale := k.Size.Add(sdf.V3{X: k.Margin, Y: k.Margin, Z: 0}).Div(k.Size)
	closing = sdf.Transform3D(closing, sdf.Scale3d(scale))
	if err != nil {
		return
	}
	bottom = sdf.Difference3D(bottom,closing)
	return
}

func InnerClosing(k *BoxParams) (closing sdf.SDF3, err error) {
	offset := math.Tan(k.Taper) * k.ClosingHeight / 2
	size := sdf.V2{X: k.Size.X, Y: k.Size.Y}
	s1 := sdf.Box2D(size.AddScalar(k.Wall-offset), k.CornerRadius)
	s2 := sdf.Box2D(size.AddScalar(k.Wall+offset), k.CornerRadius)
	closing, err = sdf.Loft3D(s1, s2, k.ClosingHeight, 0)
	if err != nil {
		return
	}
	closing = sdf.Transform3D(closing, sdf.Translate3d(sdf.V3{0,0,0.5-k.BottomTopRatio}.Mul(k.Size)))
	return
}

func OuterClosing(k *BoxParams) (closing sdf.SDF3, err error) {
	s0, err := InnerClosing(k)
	if err != nil {
		return
	}
	s1, err := baseBox3D(k)
	if err != nil {
		return
	}
	a := sdf.V3{0, 0, k.ClosingHeight / 2}
	n := sdf.V3{0, 0, -1}
	s1 = sdf.Cut3D(s1, a, n)
	s1 = sdf.Cut3D(s1, a.Neg(), n.Neg())
	closing = sdf.Difference3D(s1, s0)
	return
}