From 545a40734650c309f8f045290fc0bb6259f0ce1a Mon Sep 17 00:00:00 2001
From: Aurelien Gateau <mail@agateau.com>
Date: Fri, 11 Aug 2023 08:14:10 +0200
Subject: [PATCH] Do not draw slightly rotated vehicles on the start line

---
 .changes/unreleased/Changed-20230811-081227.yaml         | 4 ++++
 .../src/com/agateau/utils/tests/AgcMathUtilsTests.java   | 9 +++++++--
 .../com/agateau/pixelwheels/racer/VehicleRenderer.java   | 4 ++--
 core/src/com/agateau/utils/AgcMathUtils.java             | 9 +++++++--
 4 files changed, 20 insertions(+), 6 deletions(-)
 create mode 100644 .changes/unreleased/Changed-20230811-081227.yaml

diff --git a/.changes/unreleased/Changed-20230811-081227.yaml b/.changes/unreleased/Changed-20230811-081227.yaml
new file mode 100644
index 00000000..d50ca3d8
--- /dev/null
+++ b/.changes/unreleased/Changed-20230811-081227.yaml
@@ -0,0 +1,4 @@
+kind: Changed
+body: Vehicles are no longer drawn slightly rotated on the start line, making them
+  look better.
+time: 2023-08-11T08:12:27.301161038+02:00
diff --git a/core-tests/src/com/agateau/utils/tests/AgcMathUtilsTests.java b/core-tests/src/com/agateau/utils/tests/AgcMathUtilsTests.java
index 9b1fbf12..65db8376 100644
--- a/core-tests/src/com/agateau/utils/tests/AgcMathUtilsTests.java
+++ b/core-tests/src/com/agateau/utils/tests/AgcMathUtilsTests.java
@@ -141,7 +141,12 @@ public void testLineDoesNotCrossSegment() {
     @Test
     public void testSnapAngle() {
         assertThat(AgcMathUtils.snapAngle(92f), is(90f));
-        assertThat(AgcMathUtils.snapAngle(87f), is(90f));
-        assertThat(AgcMathUtils.snapAngle(183f), is(180f));
+        assertThat(AgcMathUtils.snapAngle(182f), is(180f));
+        assertThat(AgcMathUtils.snapAngle(-89f), is(-90f));
+        assertThat(AgcMathUtils.snapAngle(-92f), is(-90f));
+
+        // Untouched values
+        assertThat(AgcMathUtils.snapAngle(87f), is(87f));
+        assertThat(AgcMathUtils.snapAngle(183f), is(183f));
     }
 }
diff --git a/core/src/com/agateau/pixelwheels/racer/VehicleRenderer.java b/core/src/com/agateau/pixelwheels/racer/VehicleRenderer.java
index 72fe6633..c2b4c1fc 100644
--- a/core/src/com/agateau/pixelwheels/racer/VehicleRenderer.java
+++ b/core/src/com/agateau/pixelwheels/racer/VehicleRenderer.java
@@ -86,8 +86,8 @@ 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.
+        // Snap angles so that the vehicle body textures are not drawn 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;
diff --git a/core/src/com/agateau/utils/AgcMathUtils.java b/core/src/com/agateau/utils/AgcMathUtils.java
index 36da7a4b..cef30db5 100644
--- a/core/src/com/agateau/utils/AgcMathUtils.java
+++ b/core/src/com/agateau/utils/AgcMathUtils.java
@@ -28,6 +28,8 @@ public class AgcMathUtils {
     public static final float msToKmh = 3600 / 1000f;
     public static final float kmhToMs = 1 / msToKmh;
 
+    private static final float SNAP_ANGLE_THRESHOLD = 2;
+
     /** Wrap angles if they are less than 0 or greater than 360 */
     public static float normalizeAngle(float angle) {
         return modulo(angle, 360);
@@ -223,10 +225,13 @@ public static boolean rectangleContains(Rectangle rect, Vector2 position, float
         return true;
     }
 
+    /**
+     * Snap angle when its value is close to a multiple of 90°. "Close" means a difference of less
+     * than SNAP_ANGLE_THRESHOLD.
+     */
     public static float snapAngle(float value) {
-        value = normalizeAngle(value);
         float snappedValue = MathUtils.round(value / 90f) * 90f;
-        if (Math.abs(snappedValue - value) < 2) {
+        if (Math.abs(snappedValue - value) <= SNAP_ANGLE_THRESHOLD) {
             return snappedValue;
         }
         return value;