snap angles

.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

core-tests/src/com/agateau/utils/tests/AgcMathUtilsTests.java

@@ -137,4 +137,16 @@ 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(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));
+    }
 }

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 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;
         float yOffset =

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);
@@ -222,4 +224,16 @@ 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) {
+        float snappedValue = MathUtils.round(value / 90f) * 90f;
+        if (Math.abs(snappedValue - value) <= SNAP_ANGLE_THRESHOLD) {
+            return snappedValue;
+        }
+        return value;
+    }
 }