fix CPU cylinder for round=0

cpu_evaluators.go

@@ -62,7 +62,7 @@ func (c *cylinder) Evaluate(pos []ms3.Vec, dist []float32, userData any) error {
 	if round == 0 {
 		for i, p := range pos {
 			p = ms3.Vec{X: p.X, Y: p.Z, Z: p.Y}
-			dx := math32.Hypot(p.X, p.Y) - r
+			dx := math32.Hypot(p.X, p.Z) - r
 			dy := math32.Abs(p.Y) - h
 			dist[i] = minf(0, maxf(dx, dy)) + math32.Hypot(math32.Max(0, dx), math32.Max(0, dy))
 		}

examples/npt-flange/flange.go

@@ -98,8 +98,6 @@ func scene() (gleval.SDF3, error) {
 		Thread: threads.ISO{D: npt.D, P: 1.0 / npt.TPI},
 		Style:  threads.NutHex,
 	})
-
-	return makeSDF(pipe)
 	if err != nil {
 		return nil, err
 	}
@@ -113,6 +111,7 @@ func scene() (gleval.SDF3, error) {
 	if err != nil {
 		return nil, err
 	}
+	// return makeSDF(hole)
 	flange = gsdf.Difference(flange, hole) // Make through-hole in flange bottom
 	flange = gsdf.Scale(flange, 25.4)      // convert to millimeters
 	return makeSDF(flange)

examples/test/glsdf3test.go

@@ -66,6 +66,7 @@ var PremadePrimitives = []glbuild.Shader3D{
 	mustShader(gsdf.NewTorus(3, .5)), // Negative normal?
 	mustShader(gsdf.NewTriangularPrism(1, 2)),
 	mustShader(gsdf.NewCylinder(1, 3, .1)),
+	mustShader(gsdf.NewCylinder(1, 3, 0)), // Cylinder with no rounding.
 	mustShader(threads.Screw(5, threads.ISO{ // Negative normal.
 		D:   1,
 		P:   0.1,

primitives.go

@@ -98,13 +98,14 @@ func (s *box) Bounds() ms3.Box {
 }
 
 func NewCylinder(r, h, rounding float32) (glbuild.Shader3D, error) {
-	if rounding < 0 || rounding >= r || rounding > h/2 {
+	okRounding := rounding >= 0 && rounding < r && rounding < h/2
+	if !okRounding {
 		return nil, errors.New("invalid cylinder rounding")
 	}
-	if r <= 0 || h <= 0 {
-		return nil, errors.New("zero or negative cylinder dimension")
+	if r > 0 && h > 0 {
+		return &cylinder{r: r, h: h, round: rounding}, nil
 	}
-	return &cylinder{r: r, h: h, round: rounding}, nil
+	return nil, errors.New("bad cylinder dimension")
 }
 
 type cylinder struct {