add gasket example and symmetry2D

cpu_evaluators.go

@@ -825,3 +825,31 @@ func (t *translate2D) Evaluate(pos []ms2.Vec, dist []float32, userData any) erro
 	}
 	return sdf.Evaluate(transformed, dist, userData)
 }
+
+func (s *symmetry2D) Evaluate(pos []ms2.Vec, dist []float32, userData any) error {
+	sdf, err := gleval.AssertSDF2(s.s)
+	if err != nil {
+		return err
+	}
+	vp, err := gleval.GetVecPool(userData)
+	if err != nil {
+		return err
+	}
+	transformed := vp.V2.Acquire(len(pos))
+	copy(transformed, pos)
+	defer vp.V2.Release(transformed)
+	xb, yb := s.xy.X(), s.xy.Y()
+	for i, p := range transformed {
+		if xb {
+			transformed[i].X = absf(p.X)
+		}
+		if yb {
+			transformed[i].Y = absf(p.Y)
+		}
+	}
+	err = sdf.Evaluate(transformed, dist, userData)
+	if err != nil {
+		return err
+	}
+	return nil
+}

examples/gasket/main.go

@@ -0,0 +1,118 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"runtime"
+	"time"
+
+	"os"
+
+	"github.com/soypat/glgl/math/ms2"
+	"github.com/soypat/gsdf"
+	"github.com/soypat/gsdf/glbuild"
+	"github.com/soypat/gsdf/gsdfaux"
+)
+
+const (
+	stl             = "gasket.stl"
+	visualization   = "gasket.glsl"
+	visualization2D = "gasket2D.png"
+)
+
+func init() {
+	runtime.LockOSThread() // In case we wish to use OpenGL.
+}
+
+// scene returns the showerhead object.
+func scene() (glbuild.Shader3D, error) {
+	// Sistema Food Storage Container geometry definitions.
+	// The problem we are trying to solve is how the container is not airtight
+	// due to the o-ring not sealing against the lid. We can aid the o-ring
+	// by adding a gasket that sits in the lid so that it fills the empty space
+	// between lid and o-ring. This particular example is for the common 1 liter tupper.
+	const (
+		tupperW             = 96.
+		tupperL             = 156.
+		tupperLStartRound   = 154.
+		channelW            = 4.15
+		round               = 10.
+		extRound            = round + 1.2*channelW
+		channelWall         = 0.78
+		tupperLArcRadius    = tupperL * 2.4
+		extTupperLArcRadius = tupperLArcRadius + channelW
+	)
+	// Our gasket constructive geometry definitions.
+	const (
+		gasketHeight = 1
+		tol          = 0.8     // remove material from channel walls.
+		eps          = 1 + tol // Prevent from offset from opening symmetry edges.
+	)
+
+	var poly ms2.PolygonBuilder
+	poly.AddXY(tupperL/2, -eps)
+	poly.AddXY(tupperLStartRound/2, tupperW/2-round).Arc(tupperLArcRadius, 5)
+	poly.AddXY(tupperLStartRound/2-round, tupperW/2).Arc(round, 6)
+	poly.AddXY(-eps, tupperW/2)
+	poly.AddXY(-eps, tupperW/2+channelW)
+	poly.AddXY(tupperLStartRound/2-round, tupperW/2+channelW)
+	poly.AddXY(tupperLStartRound/2+channelW, tupperW/2-2*channelW).Arc(-extRound, 6)
+	poly.AddXY(tupperL/2+channelW, -eps).Arc(-extTupperLArcRadius, 5)
+
+	verts, err := poly.AppendVecs(nil)
+	if err != nil {
+		return nil, err
+	}
+	poly2, err := gsdf.NewPolygon(verts)
+	if err != nil {
+		return nil, err
+	}
+	poly2 = gsdf.Symmetry2D(poly2, true, true)
+	poly2 = gsdf.Offset2D(poly2, tol)
+	if visualization2D != "" {
+		start := time.Now()
+		err = gsdfaux.RenderPNGFile(visualization2D, poly2, 500, false, nil)
+		if err != nil {
+			return nil, err
+		}
+		fmt.Println("wrote 2D visualization to", visualization2D, "in", time.Since(start))
+	}
+	return gsdf.Extrude(poly2, gasketHeight)
+}
+
+func run() error {
+	useGPU := flag.Bool("gpu", false, "Enable GPU usage")
+	flag.Parse()
+	object, err := scene()
+	if err != nil {
+		return err
+	}
+	fpstl, err := os.Create(stl)
+	if err != nil {
+		return err
+	}
+	defer fpstl.Close()
+	fpvis, err := os.Create(visualization)
+	if err != nil {
+		return err
+	}
+	defer fpvis.Close()
+
+	err = gsdfaux.Render(object, gsdfaux.RenderConfig{
+		STLOutput:    fpstl,
+		VisualOutput: fpvis,
+		Resolution:   object.Bounds().Diagonal() / 350,
+		UseGPU:       *useGPU,
+	})
+
+	return err
+}
+
+func main() {
+	err := run()
+	if err != nil {
+		log.Fatal(err)
+	}
+	fmt.Println("gasket example done")
+}

go.mod

@@ -5,7 +5,7 @@ go 1.22.1
 require (
 	github.com/chewxy/math32 v1.11.0
 	github.com/go-gl/gl v0.0.0-20231021071112-07e5d0ea2e71
-	github.com/soypat/glgl v0.0.0-20240825222736-8a9aeb4f4a8f
+	github.com/soypat/glgl v0.0.0-20240831170050-86f4279df7c9
 )
 
 require (

go.sum

@@ -10,5 +10,7 @@ github.com/soypat/glgl v0.0.0-20240825114214-5f981c176edb h1:pcHDn+P2dG5wf0f65OV
 github.com/soypat/glgl v0.0.0-20240825114214-5f981c176edb/go.mod h1:ltzeLFgrGFBm2SBy10lH5IonqEdg9IkL30yam6QHMRs=
 github.com/soypat/glgl v0.0.0-20240825222736-8a9aeb4f4a8f h1:TzJXvi/Y8E96YM8ZzTk8gtD5J6EJOOras1q617qoAAQ=
 github.com/soypat/glgl v0.0.0-20240825222736-8a9aeb4f4a8f/go.mod h1:ltzeLFgrGFBm2SBy10lH5IonqEdg9IkL30yam6QHMRs=
+github.com/soypat/glgl v0.0.0-20240831170050-86f4279df7c9 h1:uEm1bHTWa8mY77k/VVaUcCyKn/ZtpLXMN5Xg4eCrsMw=
+github.com/soypat/glgl v0.0.0-20240831170050-86f4279df7c9/go.mod h1:ltzeLFgrGFBm2SBy10lH5IonqEdg9IkL30yam6QHMRs=
 golang.org/x/exp v0.0.0-20221230185412-738e83a70c30 h1:m9O6OTJ627iFnN2JIWfdqlZCzneRO6EEBsHXI25P8ws=
 golang.org/x/exp v0.0.0-20221230185412-738e83a70c30/go.mod h1:CxIveKay+FTh1D0yPZemJVgC/95VzuuOLq5Qi4xnoYc=

gsdf2d.go

@@ -633,7 +633,11 @@ type offset2D struct {
 }
 
 func (u *offset2D) Bounds() ms2.Box {
+	// TODO: this does not seem right. Removing if statement breaks gasket example STL.
 	bb := u.s.Bounds()
+	if u.f > 0 {
+		return bb
+	}
 	bb.Max = ms2.AddScalar(-u.f, bb.Max)
 	bb.Min = ms2.AddScalar(u.f, bb.Min)
 	return bb
@@ -694,3 +698,51 @@ func (s *translate2D) AppendShaderBody(b []byte) []byte {
 	b = append(b, "(p-t);"...)
 	return b
 }
+
+// Symmetry reflects the SDF around one or more cartesian planes.
+func Symmetry2D(s glbuild.Shader2D, mirrorX, mirrorY bool) glbuild.Shader2D {
+	if !mirrorX && !mirrorY {
+		panic("ineffective symmetry")
+	}
+
+	return &symmetry2D{s: s, xy: glbuild.NewXYZBits(mirrorX, mirrorY, false)}
+}
+
+type symmetry2D struct {
+	s  glbuild.Shader2D
+	xy glbuild.XYZBits
+}
+
+func (u *symmetry2D) Bounds() ms2.Box {
+	box := u.s.Bounds()
+	if u.xy.X() {
+		box.Min.X = minf(box.Min.X, -box.Max.X)
+	}
+	if u.xy.Y() {
+		box.Min.Y = minf(box.Min.Y, -box.Max.Y)
+	}
+	return box
+}
+
+func (s *symmetry2D) ForEach2DChild(userData any, fn func(userData any, s *glbuild.Shader2D) error) error {
+	return fn(userData, &s.s)
+}
+
+func (s *symmetry2D) AppendShaderName(b []byte) []byte {
+	b = append(b, "symmetry2D"...)
+	b = s.xy.AppendMapped_XYZ(b)
+	b = append(b, '_')
+	b = s.s.AppendShaderName(b)
+	return b
+}
+
+func (s *symmetry2D) AppendShaderBody(b []byte) []byte {
+	b = append(b, "p."...)
+	b = s.xy.AppendMapped_xyz(b)
+	b = append(b, "=abs(p."...)
+	b = s.xy.AppendMapped_xyz(b)
+	b = append(b, ");\n return "...)
+	b = s.s.AppendShaderName(b)
+	b = append(b, "(p);"...)
+	return b
+}