diff --git a/.github/workflows/go.yml b/.github/workflows/go.yml
index 44208b4..eb24f97 100644
--- a/.github/workflows/go.yml
+++ b/.github/workflows/go.yml
@@ -10,43 +10,26 @@ on:
     branches: [ "main" ]
 
 jobs:
-
-  build-windows:
-    name: Windows
-    runs-on: windows-latest
-    steps:
-    - uses: actions/checkout@v3
-
-    - name: Set up Go
-      uses: actions/setup-go@v3
-      with:
-        go-version: 1.22
-
-    - name: Build
-      run: go build -v ./...
-
-    - name: Test
-      run: go test -v ./...
-
-  build-mac:
-    name: MacOS
-    runs-on: macos-latest-xlarge
-    steps:
-    - uses: actions/checkout@v3
-
-    - name: Setup GPU drivers
-      run: brew install mesa
-
-    - name: Set up Go
-      uses: actions/setup-go@v3
-      with:
-        go-version: 1.22
-
-    - name: Build
-      run: go build -v ./...
-
-    - name: Test
-      run: go test -v ./...
+  # Requires paying for GPU access.
+  # build-mac:
+  #   name: MacOS
+  #   runs-on: macos-latest-xlarge
+  #   steps:
+  #   - uses: actions/checkout@v3
+
+  #   - name: Setup GPU drivers
+  #     run: brew install mesa
+
+  #   - name: Set up Go
+  #     uses: actions/setup-go@v3
+  #     with:
+  #       go-version: 1.22
+
+  #   - name: Build
+  #     run: go build -v ./...
+
+  #   - name: Test
+  #     run: go test -v ./...
 
   build-linux:
     name: Linux
diff --git a/examples/ui-geb/uigeb.go b/examples/ui-geb/uigeb.go
new file mode 100644
index 0000000..f09a69a
--- /dev/null
+++ b/examples/ui-geb/uigeb.go
@@ -0,0 +1,94 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"math"
+	"runtime"
+
+	"github.com/soypat/glgl/math/ms2"
+	"github.com/soypat/glgl/math/ms3"
+	"github.com/soypat/gsdf"
+	"github.com/soypat/gsdf/forge/textsdf"
+	"github.com/soypat/gsdf/glbuild"
+	"github.com/soypat/gsdf/gsdfaux"
+)
+
+func init() {
+	runtime.LockOSThread()
+}
+
+// scene generates the 3D object for rendering.
+func scene(bld *gsdf.Builder) (glbuild.Shader3D, error) {
+	// We create the cover of Gödel, Escher, Bach: an Eternal Golden Braid.
+	var f textsdf.Font
+	f.Configure(textsdf.FontConfig{
+		RelativeGlyphTolerance: 0.01,
+	})
+	err := f.LoadTTFBytes(textsdf.ISO3098TTF())
+	if err != nil {
+		return nil, err
+	}
+	G, _ := f.Glyph('G')
+	E, _ := f.Glyph('E')
+	B, _ := f.Glyph('B')
+
+	bbG := G.Bounds()
+	bbE := E.Bounds()
+	bbB := B.Bounds()
+	fmt.Println(bbG, bbE, bbB)
+	// return nil, errors.New("basdasd")
+	szG := bbG.Size()
+	szE := bbE.Size()
+	szB := bbB.Size()
+
+	// Match center between letters.
+	G = bld.Translate2D(G, -szG.X/2, -szG.Y/2)
+	E = bld.Translate2D(E, -szE.X/2, -szE.Y/2)
+	B = bld.Translate2D(B, -szB.X/2, -szB.Y/2)
+
+	// GEB size. Scale all letters to match size.
+	szz := ms2.MaxElem(szG, ms2.MaxElem(szE, szB)).Max()
+	sz := ms2.Vec{X: szz, Y: szz}
+	sclG := ms2.DivElem(sz, szG)
+	sclE := ms2.DivElem(sz, szE)
+	sclB := ms2.DivElem(sz, szB)
+	fmt.Println(sclG, sclE, sclB)
+	// Create 3D letters.
+	L := sz.Max()
+	G3 := bld.Extrude(G, L)
+	E3 := bld.Extrude(E, L)
+	B3 := bld.Extrude(B, L)
+
+	// Non-uniform scaling to fill letter intersections.
+	G3 = bld.Transform(G3, ms3.ScaleMat4(ms3.Vec{X: sclG.X, Y: sclG.Y, Z: 1}))
+	E3 = bld.Transform(E3, ms3.ScaleMat4(ms3.Vec{X: sclE.X, Y: sclE.Y, Z: 1}))
+	B3 = bld.Transform(B3, ms3.ScaleMat4(ms3.Vec{X: sclB.X, Y: sclB.Y, Z: 1}))
+
+	// Orient letters.
+	const deg90 = math.Pi / 2
+	E3 = bld.Rotate(E3, deg90, ms3.Vec{Y: 1})
+	B3 = bld.Rotate(B3, -deg90, ms3.Vec{X: 1})
+
+	GEB := bld.Intersection(G3, E3)
+	GEB = bld.Intersection(GEB, B3)
+	// return bld.Union(G3, E3, B3), bld.Err() // For debugging.
+	return GEB, bld.Err()
+}
+
+func main() {
+	var bld gsdf.Builder
+	shape, err := scene(&bld)
+	shape = bld.Scale(shape, 0.3)
+	if err != nil {
+		log.Fatal("creating scene:", err)
+	}
+	fmt.Println("Running UI... compiling text shaders may take a while...")
+	err = gsdfaux.UI(shape, gsdfaux.UIConfig{
+		Width:  800,
+		Height: 600,
+	})
+	if err != nil {
+		log.Fatal("UI:", err)
+	}
+}
diff --git a/examples/ui-text/uitext.go b/examples/ui-text/uitext.go
index 1c3ba44..211354c 100644
--- a/examples/ui-text/uitext.go
+++ b/examples/ui-text/uitext.go
@@ -19,6 +19,9 @@ func init() {
 // scene generates the 3D object for rendering.
 func scene(bld *gsdf.Builder) (glbuild.Shader3D, error) {
 	var f textsdf.Font
+	f.Configure(textsdf.FontConfig{
+		RelativeGlyphTolerance: 0.15,
+	})
 	err := f.LoadTTFBytes(textsdf.ISO3098TTF())
 	if err != nil {
 		return nil, err
@@ -28,6 +31,8 @@ func scene(bld *gsdf.Builder) (glbuild.Shader3D, error) {
 	if err != nil {
 		return nil, err
 	}
+	line = bld.Scale2D(line, 10) // Scale to prevent numeric error.
+
 	// Find characteristic size of characters(glyphs/letters).
 	len := utf8.RuneCountInString(text)
 	sz := line.Bounds().Size()
diff --git a/forge/textsdf/font.go b/forge/textsdf/font.go
index 309c5ff..063793a 100644
--- a/forge/textsdf/font.go
+++ b/forge/textsdf/font.go
@@ -16,6 +16,11 @@ import (
 const firstBasic = '!'
 const lastBasic = '~'
 
+type FontConfig struct {
+	// RelativeGlyphTolerance sets the permissible curve tolerance for glyphs. Must be between 0..1. If zero a reasonable value is chosen.
+	RelativeGlyphTolerance float32
+}
+
 // Font implements font parsing and glyph (character) generation.
 type Font struct {
 	ttf truetype.Font
@@ -25,6 +30,16 @@ type Font struct {
 	// Other kinds of glyphs.
 	otherGlyphs map[rune]glyph
 	bld         gsdf.Builder
+	reltol      float32 // Set by config or reset call if zeroed.
+}
+
+func (f *Font) Configure(cfg FontConfig) error {
+	if cfg.RelativeGlyphTolerance < 0 || cfg.RelativeGlyphTolerance >= 1 {
+		return errors.New("invalid RelativeGlyphTolerance")
+	}
+	f.reset()
+	f.reltol = cfg.RelativeGlyphTolerance
+	return nil
 }
 
 // LoadTTFBytes loads a TTF file blob into f. After calling Load the Font is ready to generate text SDFs.
@@ -50,6 +65,9 @@ func (f *Font) reset() {
 			delete(f.otherGlyphs, k)
 		}
 	}
+	if f.reltol == 0 {
+		f.reltol = 0.15
+	}
 }
 
 type glyph struct {
@@ -63,7 +81,8 @@ func (f *Font) TextLine(s string) (glbuild.Shader2D, error) {
 	var shapes []glbuild.Shader2D
 	scale := f.scale()
 	var idxPrev truetype.Index
-	var xOfs float32
+	var xOfs int64
+	scalout := f.scaleout()
 	for ic, c := range s {
 		if !unicode.IsGraphic(c) {
 			return nil, fmt.Errorf("char %q not graphic", c)
@@ -75,7 +94,7 @@ func (f *Font) TextLine(s string) (glbuild.Shader2D, error) {
 			if c == '\t' {
 				hm.AdvanceWidth *= 4
 			}
-			xOfs += float32(hm.AdvanceWidth)
+			xOfs += int64(hm.AdvanceWidth)
 			continue
 		}
 		charshape, err := f.Glyph(c)
@@ -84,14 +103,14 @@ func (f *Font) TextLine(s string) (glbuild.Shader2D, error) {
 		}
 
 		kern := f.ttf.Kern(scale, idxPrev, idx)
-		xOfs += float32(kern)
+		xOfs += int64(kern)
 		idxPrev = idx
 		if ic == 0 {
-			xOfs += float32(hm.LeftSideBearing)
+			xOfs += int64(hm.LeftSideBearing)
 		}
-		charshape = f.bld.Translate2D(charshape, xOfs, 0)
+		charshape = f.bld.Translate2D(charshape, float32(xOfs)*scalout, 0)
 		shapes = append(shapes, charshape)
-		xOfs += float32(hm.AdvanceWidth)
+		xOfs += int64(hm.AdvanceWidth)
 	}
 	if len(shapes) == 1 {
 		return shapes[0], nil
@@ -144,6 +163,21 @@ func (f *Font) scale() fixed.Int26_6 {
 	return fixed.Int26_6(f.ttf.FUnitsPerEm())
 }
 
+func (f *Font) rawbounds() ms2.Box {
+	bb := f.ttf.Bounds(f.scale())
+	return ms2.Box{
+		Min: ms2.Vec{X: float32(bb.Min.X), Y: float32(bb.Min.Y)},
+		Max: ms2.Vec{X: float32(bb.Max.X), Y: float32(bb.Max.Y)},
+	}
+}
+
+// scaleout defines the scaling from fixed point integers to
+func (f *Font) scaleout() float32 {
+	bb := f.rawbounds()
+	sz := bb.Size().Min()
+	return 1. / float32(sz)
+}
+
 func (f *Font) makeGlyph(char rune) (glyph, error) {
 	g := &f.gb
 	bld := &f.bld
@@ -155,9 +189,11 @@ func (f *Font) makeGlyph(char rune) (glyph, error) {
 	if err != nil {
 		return glyph{}, err
 	}
+	scaleout := f.scaleout()
 
+	tol := f.reltol
 	// Build Glyph.
-	shape, fill, err := glyphCurve(bld, g.Points, 0, g.Ends[0])
+	shape, fill, err := glyphCurve(bld, g.Points, 0, g.Ends[0], tol, scaleout)
 	if err != nil {
 		return glyph{}, err
 	} else if !fill {
@@ -167,7 +203,7 @@ func (f *Font) makeGlyph(char rune) (glyph, error) {
 	start := g.Ends[0]
 	g.Ends = g.Ends[1:]
 	for _, end := range g.Ends {
-		sdf, fill, err := glyphCurve(bld, g.Points, start, end)
+		sdf, fill, err := glyphCurve(bld, g.Points, start, end, tol, scaleout)
 		start = end
 		if err != nil {
 			return glyph{}, err
@@ -181,20 +217,20 @@ func (f *Font) makeGlyph(char rune) (glyph, error) {
 	return glyph{sdf: shape}, nil
 }
 
-func glyphCurve(bld *gsdf.Builder, points []truetype.Point, start, end int) (glbuild.Shader2D, bool, error) {
+func glyphCurve(bld *gsdf.Builder, points []truetype.Point, start, end int, tol, scale float32) (glbuild.Shader2D, bool, error) {
 	var (
-		sampler = ms2.Spline3Sampler{Spline: quadBezier, Tolerance: 0.1}
+		sampler = ms2.Spline3Sampler{Spline: quadBezier, Tolerance: tol}
 		sum     float32
 	)
 	points = points[start:end]
 	n := len(points)
 	i := 0
 	var poly []ms2.Vec
-	vPrev := p2v(points[n-1])
+	vPrev := p2v(points[n-1], scale)
 	for i < n {
 		p0, p1, p2 := points[i], points[(i+1)%n], points[(i+2)%n]
 		onBits := onbits3(points, 0, n, i)
-		v0, v1, v2 := p2v(p0), p2v(p1), p2v(p2)
+		v0, v1, v2 := p2v(p0, scale), p2v(p1, scale), p2v(p2, scale)
 		implicit0 := ms2.Scale(0.5, ms2.Add(v0, v1))
 		implicit1 := ms2.Scale(0.5, ms2.Add(v1, v2))
 		switch onBits {
@@ -232,17 +268,17 @@ func glyphCurve(bld *gsdf.Builder, points []truetype.Point, start, end int) (glb
 			i += 2
 		}
 		poly = append(poly, v0) // Append start point.
-		poly = sampler.SampleBisect(poly, 1)
+		poly = sampler.SampleBisect(poly, 4)
 		sum += (v0.X - vPrev.X) * (v0.Y + vPrev.Y)
 		vPrev = v0
 	}
 	return bld.NewPolygon(poly), sum > 0, bld.Err()
 }
 
-func p2v(p truetype.Point) ms2.Vec {
+func p2v(p truetype.Point, scale float32) ms2.Vec {
 	return ms2.Vec{
-		X: float32(p.X),
-		Y: float32(p.Y),
+		X: float32(p.X) * scale,
+		Y: float32(p.Y) * scale,
 	}
 }
 
diff --git a/go.mod b/go.mod
index dfa4ee0..2d31fb4 100644
--- a/go.mod
+++ b/go.mod
@@ -5,13 +5,11 @@ go 1.22.1
 require (
 	github.com/chewxy/math32 v1.11.1
 	github.com/go-gl/gl v0.0.0-20231021071112-07e5d0ea2e71
+	github.com/go-gl/glfw v0.0.0-20221017161538-93cebf72946b
 	github.com/go-gl/glfw/v3.3/glfw v0.0.0-20221017161538-93cebf72946b
 	github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0
 	github.com/soypat/glgl v0.0.0-20241121001014-cc8498d2a83d
+	golang.org/x/image v0.22.0
 )
 
-require (
-	github.com/go-gl/glfw v0.0.0-20221017161538-93cebf72946b // indirect
-	golang.org/x/exp v0.0.0-20221230185412-738e83a70c30 // indirect
-	golang.org/x/image v0.22.0 // indirect
-)
+require golang.org/x/exp v0.0.0-20221230185412-738e83a70c30 // indirect
diff --git a/go.sum b/go.sum
index 5e3eab8..147c78f 100644
--- a/go.sum
+++ b/go.sum
@@ -8,10 +8,6 @@ github.com/go-gl/glfw/v3.3/glfw v0.0.0-20221017161538-93cebf72946b h1:GgabKamyOY
 github.com/go-gl/glfw/v3.3/glfw v0.0.0-20221017161538-93cebf72946b/go.mod h1:tQ2UAYgL5IevRw8kRxooKSPJfGvJ9fJQFa0TUsXzTg8=
 github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0 h1:DACJavvAHhabrF08vX0COfcOBJRhZ8lUbR+ZWIs0Y5g=
 github.com/golang/freetype v0.0.0-20170609003504-e2365dfdc4a0/go.mod h1:E/TSTwGwJL78qG/PmXZO1EjYhfJinVAhrmmHX6Z8B9k=
-github.com/soypat/glgl v0.0.0-20241019203012-a2ad2ed164c2 h1:N/GkdilItOR9bBrGXIj+53DbxUzRnG1SF/aOkBQzlxs=
-github.com/soypat/glgl v0.0.0-20241019203012-a2ad2ed164c2/go.mod h1:1LcEp6XHSMCI91WlJHzl/aW4Bp5v6yQOiYFyjrlk350=
-github.com/soypat/glgl v0.0.0-20241117161642-84ce0213c9ea h1:bPlNmRe3fBJQPzqNWUN2ChFZJgGo+jk056+wpAzEX+w=
-github.com/soypat/glgl v0.0.0-20241117161642-84ce0213c9ea/go.mod h1:1LcEp6XHSMCI91WlJHzl/aW4Bp5v6yQOiYFyjrlk350=
 github.com/soypat/glgl v0.0.0-20241121001014-cc8498d2a83d h1:kDdWM661L/RAxg0j4gV+18hky7/3Tvbhd8O6p8CLB7w=
 github.com/soypat/glgl v0.0.0-20241121001014-cc8498d2a83d/go.mod h1:1LcEp6XHSMCI91WlJHzl/aW4Bp5v6yQOiYFyjrlk350=
 golang.org/x/exp v0.0.0-20221230185412-738e83a70c30 h1:m9O6OTJ627iFnN2JIWfdqlZCzneRO6EEBsHXI25P8ws=
diff --git a/gsdf2d.go b/gsdf2d.go
index e2fff5e..0c5835e 100644
--- a/gsdf2d.go
+++ b/gsdf2d.go
@@ -1235,3 +1235,40 @@ func (ca *circarray2D) AppendShaderBody(b []byte) []byte {
 func (u *circarray2D) AppendShaderObjects(objects []glbuild.ShaderObject) []glbuild.ShaderObject {
 	return objects
 }
+
+// ScaleXY scales s by scaleFactor around the origin.
+func (bld *Builder) Scale2D(s glbuild.Shader2D, scale float32) glbuild.Shader2D {
+	return &scale2D{s: s, scale: scale}
+}
+
+type scale2D struct {
+	s     glbuild.Shader2D
+	scale float32
+}
+
+func (u *scale2D) Bounds() ms2.Box {
+	b := u.s.Bounds()
+	return b.Scale(ms2.Vec{X: u.scale, Y: u.scale})
+}
+
+func (s *scale2D) ForEach2DChild(userData any, fn func(userData any, s *glbuild.Shader2D) error) error {
+	return fn(userData, &s.s)
+}
+
+func (s *scale2D) AppendShaderName(b []byte) []byte {
+	b = append(b, "scalexy_"...)
+	b = s.s.AppendShaderName(b)
+	return b
+}
+
+func (s *scale2D) AppendShaderBody(b []byte) []byte {
+	b = glbuild.AppendFloatDecl(b, "s", s.scale)
+	b = append(b, "return "...)
+	b = s.s.AppendShaderName(b)
+	b = append(b, "(p/s)*s;"...)
+	return b
+}
+
+func (u *scale2D) AppendShaderObjects(objects []glbuild.ShaderObject) []glbuild.ShaderObject {
+	return objects
+}
diff --git a/gsdfaux/gsdfaux.go b/gsdfaux/gsdfaux.go
index 6070350..e3e7c64 100644
--- a/gsdfaux/gsdfaux.go
+++ b/gsdfaux/gsdfaux.go
@@ -39,7 +39,7 @@ type RenderConfig struct {
 
 type UIConfig struct {
 	Width, Height int
-	Ctx           context.Context
+	Context       context.Context
 }
 
 func UI(s glbuild.Shader3D, cfg UIConfig) error {
diff --git a/gsdfaux/ui.go b/gsdfaux/ui.go
index 5cff5c7..e5e4971 100644
--- a/gsdfaux/ui.go
+++ b/gsdfaux/ui.go
@@ -169,13 +169,20 @@ void main() {
 				isMousePressed = false
 				window.SetInputMode(glfw.CursorMode, glfw.CursorNormal)
 			}
-
 		}
 	})
 
 	// Main render loop
 	previousTime := glfw.GetTime()
+	ctx := cfg.Context
 	for !window.ShouldClose() {
+		if ctx != nil {
+			select {
+			case <-ctx.Done():
+				return ctx.Err()
+			default:
+			}
+		}
 		width, height := window.GetSize()
 		currentTime := glfw.GetTime()
 		elapsedTime := currentTime - previousTime