Add Translate2D; fix gsdfaux.RenderImage inverted y axis

cpu_evaluators.go

@@ -807,3 +807,21 @@ func (r *offset2D) Evaluate(pos []ms2.Vec, dist []float32, userData any) error {
 	}
 	return nil
 }
+
+func (t *translate2D) Evaluate(pos []ms2.Vec, dist []float32, userData any) error {
+	sdf, err := gleval.AssertSDF2(t.s)
+	if err != nil {
+		return err
+	}
+	vp, err := gleval.GetVecPool(userData)
+	if err != nil {
+		return err
+	}
+	transformed := vp.V2.Acquire(len(pos))
+	defer vp.V2.Release(transformed)
+	T := t.p
+	for i, p := range pos {
+		transformed[i] = ms2.Sub(p, T)
+	}
+	return sdf.Evaluate(transformed, dist, userData)
+}

examples/image/image.go

@@ -31,11 +31,12 @@ func scene() (glbuild.Shader2D, error) {
 }
 
 func main() {
+	useGPU := false
 	s, err := scene()
 	if err != nil {
 		log.Fatal(err)
 	}
-	err = gsdfaux.RenderPNGFile(filename, s, 1080, nil)
+	err = gsdfaux.RenderPNGFile(filename, s, 1080, useGPU, nil)
 	if err != nil {
 		log.Fatal(err)
 	}

glrender/image.go

@@ -87,7 +87,9 @@ func (ir *ImageRendererSDF2) Render(sdf gleval.SDF2, img setImage, userData any)
 	bb.Min = ms2.Add(bb.Min, ms2.Vec{X: dx / 2, Y: dy / 2}) // Offset to center image.
 	// Keep track of next index to start reading.
 	for j := 0; j < dyi; j++ {
-		y := float32(j)*dy + bb.Min.Y
+		// y is inverted in the image interface, maximum index (maxI, maxJ) represents upper left corner.
+		// See [image.At] method so we must invert y here.
+		y := bb.Max.Y - (float32(j)*dy + bb.Min.Y)
 		err := ir.renderRow(sdf, j, y, bb.Min.X, dx, imgBB, img, userData)
 		if err != nil {
 			return err

gsdf2d.go

@@ -659,3 +659,38 @@ func (s *offset2D) AppendShaderBody(b []byte) []byte {
 	b = append(b, ')', ';')
 	return b
 }
+
+// Translate2D moves the SDF s in the given direction.
+func Translate2D(s glbuild.Shader2D, dirX, dirY float32) glbuild.Shader2D {
+	return &translate2D{s: s, p: ms2.Vec{X: dirX, Y: dirY}}
+}
+
+type translate2D struct {
+	s glbuild.Shader2D
+	p ms2.Vec
+}
+
+func (u *translate2D) Bounds() ms2.Box {
+	return u.s.Bounds().Add(u.p)
+}
+
+func (s *translate2D) ForEach2DChild(userData any, fn func(userData any, s *glbuild.Shader2D) error) error {
+	return fn(userData, &s.s)
+}
+
+func (s *translate2D) AppendShaderName(b []byte) []byte {
+	b = append(b, "translate2D"...)
+	arr := s.p.Array()
+	b = glbuild.AppendFloats(b, 0, 'n', 'p', arr[:]...)
+	b = append(b, '_')
+	b = s.s.AppendShaderName(b)
+	return b
+}
+
+func (s *translate2D) AppendShaderBody(b []byte) []byte {
+	b = glbuild.AppendVec2Decl(b, "t", s.p)
+	b = append(b, "return "...)
+	b = s.s.AppendShaderName(b)
+	b = append(b, "(p-t);"...)
+	return b
+}

gsdfaux/gsdfaux.go

@@ -142,7 +142,10 @@ func stopwatch() func() time.Duration {
 // RenderPNGFile renders a 2D SDF as an image and saves result to a PNG file with said filename.
 // The image width is sized automatically from the image height argument to preserve SDF aspect ratio.
 // If a nil color conversion function is passed then one is automatically chosen.
-func RenderPNGFile(filename string, s glbuild.Shader2D, picHeight int, colorConversion func(float32) color.Color) error {
+func RenderPNGFile(filename string, s glbuild.Shader2D, picHeight int, useGPU bool, colorConversion func(float32) color.Color) error {
+	if useGPU {
+		return errors.New("TODO: implement GPU rendering for RenderPNGFile")
+	}
 	bb := s.Bounds()
 	sz := bb.Size()
 	if colorConversion == nil {
@@ -155,6 +158,7 @@ func RenderPNGFile(filename string, s glbuild.Shader2D, picHeight int, colorConv
 	if err != nil {
 		return err
 	}
+
 	sdf, err := gleval.NewCPUSDF2(s)
 	if err != nil {
 		return err