PhysicsRigidBody: implement the friction parameter

stephengold · Jun 20, 2024 · 25e1374 · 25e1374
1 parent 1923aef
commit 25e1374
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Showing 2 changed files with 32 additions and 0 deletions.
diff --git a/library/src/main/java/com/jme3/bullet/objects/PhysicsRigidBody.java b/library/src/main/java/com/jme3/bullet/objects/PhysicsRigidBody.java
@@ -181,6 +181,17 @@ public Vec3d getAngularVelocityDp(Vec3d storeResult) {
         return result;
     }
 
+    /**
+     * Return the body's friction parameter.
+     *
+     * @return the parameter value (&ge;0)
+     */
+    public float getFriction() {
+        float result = joltBody.getFriction();
+        assert result >= 0f : result;
+        return result;
+    }
+
     /**
      * Copy the linear velocity of the body's center of mass. The body must be
      * in dynamic mode.
@@ -441,6 +452,18 @@ public void setCollisionShape(CollisionShape desiredShape) {
         rebuildRigidBody();
     }
 
+    /**
+     * Alter the body's friction.
+     *
+     * @param friction the desired friction value (&ge;0, default=0.5)
+     * <p>
+     * Note: the jolt-java default is 0.2 .
+     */
+    public void setFriction(float friction) {
+        Validate.nonNegative(friction, "friction");
+        joltBody.setFriction(friction);
+    }
+
     /**
      * Alter the linear velocity of the body's center of mass.
      *

diff --git a/library/src/main/java/com/jme3/bullet/objects/infos/RigidBodySnapshot.java b/library/src/main/java/com/jme3/bullet/objects/infos/RigidBodySnapshot.java
@@ -56,6 +56,10 @@ public class RigidBodySnapshot {
     // *************************************************************************
     // fields
 
+    /**
+     * friction parameter
+     */
+    private float friction;
     /**
      * angular velocity (in physics-space coordinates)
      */
@@ -71,6 +75,7 @@ public class RigidBodySnapshot {
      * Instantiate a snapshot with default parameters.
      */
     public RigidBodySnapshot() {
+        this.friction = 0.5f;
         this.angularVelocity = new Vec3d();
         this.linearVelocity = new Vec3d();
     }
@@ -81,6 +86,9 @@ public RigidBodySnapshot() {
      * @param body the body to capture (not null)
      */
     public RigidBodySnapshot(PhysicsRigidBody body) {
+        this.friction = body.getFriction();
+
+        // Vec3d
         if (body.isDynamic()) {
             this.angularVelocity = body.getAngularVelocityDp(null);
             this.linearVelocity = body.getLinearVelocityDp(null);
@@ -98,6 +106,7 @@ public RigidBodySnapshot(PhysicsRigidBody body) {
      * @param body the target body (not null, modified)
      */
     public void applyTo(PhysicsRigidBody body) {
+        body.setFriction(friction);
         if (body.isDynamic()) {
             body.setAngularVelocityDp(angularVelocity);
             body.setLinearVelocityDp(linearVelocity);