From c84530857c65d95955b167f12fddcf55ec10b100 Mon Sep 17 00:00:00 2001
From: Aurelien Gateau <mail@agateau.com>
Date: Tue, 25 Jul 2023 21:05:52 +0200
Subject: [PATCH] Snap angles

---
 .../src/com/agateau/utils/tests/AgcMathUtilsTests.java   | 7 +++++++
 .../com/agateau/pixelwheels/racer/VehicleRenderer.java   | 4 ++++
 core/src/com/agateau/utils/AgcMathUtils.java             | 9 +++++++++
 3 files changed, 20 insertions(+)

diff --git a/core-tests/src/com/agateau/utils/tests/AgcMathUtilsTests.java b/core-tests/src/com/agateau/utils/tests/AgcMathUtilsTests.java
index 08a2fb35b..9b1fbf122 100644
--- a/core-tests/src/com/agateau/utils/tests/AgcMathUtilsTests.java
+++ b/core-tests/src/com/agateau/utils/tests/AgcMathUtilsTests.java
@@ -137,4 +137,11 @@ public void testLineDoesNotCrossSegment() {
         assertThat(AgcMathUtils.lineCrossesSegment(l1, l2, s1, s2), is(false));
         assertThat(AgcMathUtils.lineCrossesSegment(l1, l2, s2, s1), is(false));
     }
+
+    @Test
+    public void testSnapAngle() {
+        assertThat(AgcMathUtils.snapAngle(92f), is(90f));
+        assertThat(AgcMathUtils.snapAngle(87f), is(90f));
+        assertThat(AgcMathUtils.snapAngle(183f), is(180f));
+    }
 }
diff --git a/core/src/com/agateau/pixelwheels/racer/VehicleRenderer.java b/core/src/com/agateau/pixelwheels/racer/VehicleRenderer.java
index aaf480a36..72fe66333 100644
--- a/core/src/com/agateau/pixelwheels/racer/VehicleRenderer.java
+++ b/core/src/com/agateau/pixelwheels/racer/VehicleRenderer.java
@@ -25,6 +25,7 @@
 import com.agateau.pixelwheels.gameobject.CellFrameBufferManager;
 import com.agateau.pixelwheels.gameobject.CellFrameBufferUser;
 import com.agateau.pixelwheels.utils.BodyRegionDrawer;
+import com.agateau.utils.AgcMathUtils;
 import com.badlogic.gdx.Gdx;
 import com.badlogic.gdx.graphics.Color;
 import com.badlogic.gdx.graphics.g2d.Animation;
@@ -85,6 +86,9 @@ public void init(CellFrameBufferManager manager) {
 
     private void drawBodyToCell(Batch batch, Body body, TextureRegion region) {
         float angle = body.getAngle() * MathUtils.radiansToDegrees;
+        // Snap angles so that the vehicles do not slightly rotated when facing north, south, east
+        // or west. This is especially useful at startup.
+        angle = AgcMathUtils.snapAngle(angle);
         float xOffset =
                 (body.getPosition().x - mVehicle.getPosition().x) / Constants.UNIT_FOR_PIXEL;
         float yOffset =
diff --git a/core/src/com/agateau/utils/AgcMathUtils.java b/core/src/com/agateau/utils/AgcMathUtils.java
index 25083a487..36da7a4b4 100644
--- a/core/src/com/agateau/utils/AgcMathUtils.java
+++ b/core/src/com/agateau/utils/AgcMathUtils.java
@@ -222,4 +222,13 @@ public static boolean rectangleContains(Rectangle rect, Vector2 position, float
         }
         return true;
     }
+
+    public static float snapAngle(float value) {
+        value = normalizeAngle(value);
+        float snappedValue = MathUtils.round(value / 90f) * 90f;
+        if (Math.abs(snappedValue - value) < 2) {
+            return snappedValue;
+        }
+        return value;
+    }
 }