From da8c5f73cf8442902d9eba26a545bb1f7af054e2 Mon Sep 17 00:00:00 2001
From: Shadowfacts <me@shadowfacts.net>
Date: Mon, 21 Oct 2019 11:32:18 -0400
Subject: [PATCH] Basic bezier curve rendering

---
 .../shadowfacts/cacao/geometry/BezierCurve.kt | 49 +++++++++++++++++++
 .../net/shadowfacts/cacao/geometry/Point.kt   |  7 +++
 .../shadowfacts/cacao/util/RenderHelper.kt    |  9 ++++
 .../shadowfacts/cacao/view/BezierCurveView.kt | 36 ++++++++++++++
 4 files changed, 101 insertions(+)
 create mode 100644 src/main/kotlin/net/shadowfacts/cacao/geometry/BezierCurve.kt
 create mode 100644 src/main/kotlin/net/shadowfacts/cacao/view/BezierCurveView.kt

diff --git a/src/main/kotlin/net/shadowfacts/cacao/geometry/BezierCurve.kt b/src/main/kotlin/net/shadowfacts/cacao/geometry/BezierCurve.kt
new file mode 100644
index 0000000..60a4453
--- /dev/null
+++ b/src/main/kotlin/net/shadowfacts/cacao/geometry/BezierCurve.kt
@@ -0,0 +1,49 @@
+package net.shadowfacts.cacao.geometry
+
+import java.lang.RuntimeException
+import kotlin.math.pow
+
+/**
+ * Helper class that represents a cubic bezier curve.
+ *
+ * @author shadowfacts
+ */
+data class BezierCurve(private val points: Array<Point>) {
+
+	init {
+		if (points.size != 4) {
+			throw RuntimeException("Cubic bezier curve must have exactly four points")
+		}
+	}
+
+	fun point(time: Double): Point {
+		val x = coordinate(time, Axis.HORIZONTAL)
+		val y = coordinate(time, Axis.VERTICAL)
+		return Point(x, y)
+	}
+
+	private fun coordinate(t: Double, axis: Axis): Double {
+		// B(t)=(1-t)^3*p0+3(1-t)^2*t*p1+3(1-t)*t^2*p2+t^3*p3
+		val p0 = points[0][axis]
+		val p1 = points[1][axis]
+		val p2 = points[2][axis]
+		val p3 = points[3][axis]
+		return ((1 - t).pow(3) * p0) + (3 * (1 - t).pow(2) * t * p1) + (3 * (1 - t) * t.pow(2) * p2) + (t.pow(3) * p3)
+	}
+
+	override fun equals(other: Any?): Boolean {
+		if (this === other) return true
+		if (javaClass != other?.javaClass) return false
+
+		other as BezierCurve
+
+		if (!points.contentEquals(other.points)) return false
+
+		return true
+	}
+
+	override fun hashCode(): Int {
+		return points.contentHashCode()
+	}
+
+}
\ No newline at end of file
diff --git a/src/main/kotlin/net/shadowfacts/cacao/geometry/Point.kt b/src/main/kotlin/net/shadowfacts/cacao/geometry/Point.kt
index f556a6a..81406d4 100644
--- a/src/main/kotlin/net/shadowfacts/cacao/geometry/Point.kt
+++ b/src/main/kotlin/net/shadowfacts/cacao/geometry/Point.kt
@@ -21,4 +21,11 @@ data class Point(val x: Double, val y: Double) {
 		return Point(x - other.x, y - other.y)
 	}
 
+	operator fun get(axis: Axis): Double {
+		return when (axis) {
+			Axis.HORIZONTAL -> x
+			Axis.VERTICAL -> y
+		}
+	}
+
 }
\ No newline at end of file
diff --git a/src/main/kotlin/net/shadowfacts/cacao/util/RenderHelper.kt b/src/main/kotlin/net/shadowfacts/cacao/util/RenderHelper.kt
index f041167..c858c11 100644
--- a/src/main/kotlin/net/shadowfacts/cacao/util/RenderHelper.kt
+++ b/src/main/kotlin/net/shadowfacts/cacao/util/RenderHelper.kt
@@ -9,6 +9,7 @@ import net.minecraft.client.render.VertexFormat
 import net.minecraft.client.render.VertexFormats
 import net.minecraft.client.sound.PositionedSoundInstance
 import net.minecraft.sound.SoundEvent
+import net.shadowfacts.cacao.geometry.BezierCurve
 import net.shadowfacts.cacao.geometry.Point
 import net.shadowfacts.cacao.geometry.Rect
 import net.shadowfacts.cacao.util.texture.Texture
@@ -108,6 +109,14 @@ object RenderHelper {
 		GlStateManager.translated(x, y, z)
 	}
 
+	/**
+	 * @see org.lwjgl.opengl.GL11.glScaled
+	 */
+	fun scale(x: Double, y: Double, z: Double = 1.0) {
+		if (disabled) return
+		GlStateManager.scaled(x, y, z)
+	}
+
 	/**
 	 * @see org.lwjgl.opengl.GL11.glColor4f
 	 */
diff --git a/src/main/kotlin/net/shadowfacts/cacao/view/BezierCurveView.kt b/src/main/kotlin/net/shadowfacts/cacao/view/BezierCurveView.kt
new file mode 100644
index 0000000..c026f70
--- /dev/null
+++ b/src/main/kotlin/net/shadowfacts/cacao/view/BezierCurveView.kt
@@ -0,0 +1,36 @@
+package net.shadowfacts.cacao.view
+
+import com.mojang.blaze3d.platform.GlStateManager
+import net.shadowfacts.cacao.geometry.BezierCurve
+import net.shadowfacts.cacao.geometry.Point
+import net.shadowfacts.cacao.util.Color
+import net.shadowfacts.cacao.util.RenderHelper
+
+/**
+ * @author shadowfacts
+ */
+class BezierCurveView(val curve: BezierCurve): View() {
+
+	private val points by lazy {
+		val step = 0.05
+		var t = 0.0
+		val points = mutableListOf<Point>()
+		while (t <= 1) {
+			points.add(curve.point(t))
+			t += step
+		}
+		points
+	}
+
+	var lineWidth = 3f
+	var lineColor = Color.BLACK
+
+	override fun drawContent(mouse: Point, delta: Float) {
+		RenderHelper.scale(bounds.width, bounds.height)
+		for ((index, point) in points.withIndex()) {
+			val next = points.getOrNull(index + 1) ?: break
+			RenderHelper.drawLine(point, next, zIndex, lineWidth, lineColor)
+		}
+	}
+
+}
\ No newline at end of file