Decently working demo for rigidbody 1

1 files changed, 6 insertions, 4 deletions

diff --git a/2d/rigidbody/rigidbody_1/snippet3.cpp b/2d/rigidbody/rigidbody_1/snippet3.cpp
index a43c884..4727a9a 100644
--- a/2d/rigidbody/rigidbody_1/snippet3.cpp
+++ b/2d/rigidbody/rigidbody_1/snippet3.cpp
@@ -17,24 +17,26 @@ struct Rigidbody {
     void update(float32 deltaTimeSeconds) {
         applyGravity(deltaTimeSeconds);
 
-        // Add up all of the forces acting at this moment
         Vector2 force;
         for (int32 idx = 0; idx < numImpulses; idx++) {
             Impulse& i = activeImpulses[idx];
 
             float32 nextTimeAppliedSeconds = i.timeAppliedSeconds + deltaTimeSeconds;
             if (nextTimeAppliedSeconds >= i.timeOfApplicationSeconds) {
-                nextTimeAppliedSeconds = i.timeOfApplicationSeconds;
+                nextTimeAppliedSeconds = i.timeOfApplicationSeconds; // Do the remainder of the time
                 i.isDead = true;
             }
             
+            // We apply the force spread out over timeOfApplicationSeconds, so we need
+            // to calculate the fractional amount of force that was applied in this frame.
             float32 impulseDtSeconds = nextTimeAppliedSeconds - i.timeAppliedSeconds;
-            force += i.force * impulseDtSeconds;
+            Vector2 forceToApply = i.force * (impulseDtSeconds / i.timeOfApplicationSeconds);
+            force += forceToApply * impulseDtSeconds;
             i.timeAppliedSeconds = nextTimeAppliedSeconds;
         }
 
         Vector2 acceleration = force / mass;
-        velocity += (acceleration * impulseDtSeconds);
+        velocity += (acceleration * deltaTimeSeconds);
         position += (velocity * deltaTimeSeconds);
 
         // Cleanup any impulses that have expired in the mean time