From 15318301e09a9b45236aec0c47d7fdbd0123f4f5 Mon Sep 17 00:00:00 2001
From: Alex Nichol <unixpickle@gmail.com>
Date: Sun, 27 Aug 2023 13:02:49 -0700
Subject: [PATCH] whipped cream

---
 examples/usable/milkshake_ringholder/cream.go | 68 +++++++++++++++++++
 examples/usable/milkshake_ringholder/cup.go   | 17 ++++-
 examples/usable/milkshake_ringholder/main.go  | 16 ++++-
 3 files changed, 97 insertions(+), 4 deletions(-)
 create mode 100644 examples/usable/milkshake_ringholder/cream.go

diff --git a/examples/usable/milkshake_ringholder/cream.go b/examples/usable/milkshake_ringholder/cream.go
new file mode 100644
index 0000000..cca483c
--- /dev/null
+++ b/examples/usable/milkshake_ringholder/cream.go
@@ -0,0 +1,68 @@
+package main
+
+import (
+	"math"
+
+	"github.com/unixpickle/model3d/model2d"
+	"github.com/unixpickle/model3d/model3d"
+	"github.com/unixpickle/model3d/render3d"
+	"github.com/unixpickle/model3d/toolbox3d"
+)
+
+const (
+	CreamRadius  = 0.15
+	CreamHeight  = 0.8
+	CreamZOffset = 0.05
+)
+
+func CreamSolid() (model3d.Solid, toolbox3d.CoordColorFunc) {
+	mesh := CreamMesh()
+	return model3d.NewColliderSolid(model3d.MeshToCollider(mesh)),
+		toolbox3d.ConstantCoordColorFunc(render3d.NewColor(1.0))
+}
+
+func CreamMesh() *model3d.Mesh {
+	baseShape := model2d.CheckedFuncSolid(
+		model2d.Ones(-CreamRadius),
+		model2d.Ones(CreamRadius),
+		func(c model2d.Coord) bool {
+			norm := c.Norm()
+			if norm < 1e-8 {
+				return true
+			}
+			normed := c.Scale(1 / norm)
+			pow := 2.5
+			r := math.Pow(math.Pow(math.Abs(normed.X), pow)+math.Pow(math.Abs(normed.Y), pow), pow)
+			return norm/CreamRadius < r
+		},
+	)
+	length := 10.0
+	solid3d := model3d.ProfileSolid(baseShape, 0, length)
+	mesh3d := model3d.DualContour(solid3d, 0.03, true, false)
+
+	// Deform along a curve.
+	return mesh3d.MapCoords(func(c model3d.Coord3D) model3d.Coord3D {
+		centerCoord := creamCurve(c.Z / length)
+		c2 := creamCurve(c.Z/length + 1e-5)
+		derivative := c2.Sub(centerCoord).Normalize()
+		x1 := model3d.Z(1).ProjectOut(derivative)
+		x2 := x1.Cross(derivative)
+
+		// Apply a small twist along the curve.
+		rotation := c.Z / length * 25
+		x1, x2 = x1.Scale(math.Cos(rotation)).Add(x2.Scale(math.Sin(rotation))),
+			x1.Scale(-math.Sin(rotation)).Add(x2.Scale(math.Cos(rotation)))
+		return centerCoord.Add(x1.Scale(c.Y)).Add(x2.Scale(c.X))
+	})
+}
+
+func creamCurve(t float64) model3d.Coord3D {
+	theta := t * 30
+	// We want the start to naturally "tuck into" the spiral.
+	radius := (CupTopRadius - CreamRadius) * (1 - math.Abs(t*1.1-0.1))
+	return model3d.XYZ(
+		math.Cos(theta)*radius,
+		math.Sin(theta)*radius,
+		CupHeight+t*CreamHeight-CreamZOffset,
+	)
+}
diff --git a/examples/usable/milkshake_ringholder/cup.go b/examples/usable/milkshake_ringholder/cup.go
index 0e52905..204f762 100644
--- a/examples/usable/milkshake_ringholder/cup.go
+++ b/examples/usable/milkshake_ringholder/cup.go
@@ -17,6 +17,8 @@ const (
 	CupTopRadius      = 0.9
 	CupHeight         = 3
 	CupRimHeight      = 0.4
+	CupRimThickness   = 0.1
+	CupContentsDepth  = 0.1
 )
 
 func CupSolid() (model3d.Solid, toolbox3d.CoordColorFunc) {
@@ -39,9 +41,22 @@ func CupSolid() (model3d.Solid, toolbox3d.CoordColorFunc) {
 					facetDepth := math.Sqrt(1 - r*r)
 					radius -= facetDepth * CupFacetFlatten
 				}
+			} else if c.Z > CupHeight-CupContentsDepth {
+				r := c.XY().Norm()
+				return r < radius && r > radius-CupRimThickness
 			}
 			return c.XY().Norm() < radius
 		},
 	)
-	return solid, toolbox3d.ConstantCoordColorFunc(render3d.NewColorRGB(0x65/255.0, 0xbc/255.0, 0xd4/255.0))
+	colorFn := func(c model3d.Coord3D) render3d.Color {
+		fracTop := c.Z / CupHeight
+		radius := fracTop*CupTopRadius + (1-fracTop)*CupBottomRadius
+		r := c.XY().Norm()
+		if r <= radius-CupRimThickness && c.Z > CupHeight-CupRimHeight {
+			return render3d.NewColor(1.0)
+		} else {
+			return render3d.NewColorRGB(0x65/255.0, 0xbc/255.0, 0xd4/255.0)
+		}
+	}
+	return solid, colorFn
 }
diff --git a/examples/usable/milkshake_ringholder/main.go b/examples/usable/milkshake_ringholder/main.go
index eb71fee..a7dd8de 100644
--- a/examples/usable/milkshake_ringholder/main.go
+++ b/examples/usable/milkshake_ringholder/main.go
@@ -3,10 +3,20 @@ package main
 import (
 	"github.com/unixpickle/model3d/model3d"
 	"github.com/unixpickle/model3d/render3d"
+	"github.com/unixpickle/model3d/toolbox3d"
 )
 
 func main() {
-	cup, colorFn := CupSolid()
-	mesh := model3d.MarchingCubesSearch(cup, 0.02, 8)
-	render3d.SaveRandomGrid("rendering.png", mesh, 3, 3, 300, colorFn.RenderColor)
+	cup, cupColor := CupSolid()
+	cream, creamColor := CreamSolid()
+	joined := model3d.JoinedSolid{cup, cream}
+
+	mesh, interior := model3d.MarchingCubesInterior(joined, 0.02, 8)
+	colorFunc := toolbox3d.JoinedSolidCoordColorFunc(
+		interior,
+		cup, cupColor,
+		cream, creamColor,
+	)
+
+	render3d.SaveRandomGrid("rendering.png", mesh, 3, 3, 300, colorFunc.RenderColor)
 }