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struct Impulse {
Vector2 force = { 0, 0 };
Vector2 pointOfApplication = { 0, 0 };
float32 timeOfApplicationSeconds = 0.25f;
float32 timeAppliedSeconds = 0.f;
bool isDead = false;
};
const int32 NUM_IMPULSES = 4;
struct Rigidbody {
int32 numImpulses = 0;
Impulse activeImpulses[NUM_IMPULSES];
Vector2 velocity = { 0, 0 };
Vector2 position = { 0, 0 };
float32 mass = 1.f;
float32 rotationalVelocity = 0.f;
float32 rotation = 0.f;
float32 momentOfInertia = 1.f;
void reset() {
numImpulses = 0;
velocity = { 0, 0 };
rotationalVelocity = 0.f;
rotation = 0.f;
}
void applyImpulse(Impulse i) {
if (numImpulses > NUM_IMPULSES) {
printf("Unable to apply impulse. Buffer full.\n");
return;
}
activeImpulses[numImpulses] = i;
numImpulses++;
}
void applyGravity(float32 deltaTimeSeconds) {
velocity += (Vector2 { 0.f, -9.8f } * deltaTimeSeconds);
}
void update(float32 deltaTimeSeconds) {
applyGravity(deltaTimeSeconds);
Vector2 force;
float32 torque = 0.f;
for (int32 idx = 0; idx < numImpulses; idx++) {
Impulse& i = activeImpulses[idx];
float32 nextTimeAppliedSeconds = i.timeAppliedSeconds + deltaTimeSeconds;
if (nextTimeAppliedSeconds >= i.timeOfApplicationSeconds) {
nextTimeAppliedSeconds = i.timeOfApplicationSeconds;
i.isDead = true;
}
float32 impulseDtSeconds = nextTimeAppliedSeconds - i.timeAppliedSeconds;
Vector2 forceToApply = i.force * (impulseDtSeconds / i.timeOfApplicationSeconds);
force += forceToApply * impulseDtSeconds;
// New! Increment the torque for each force
torque += i.pointOfApplication.getPerp().dot(forceToApply);
i.timeAppliedSeconds = nextTimeAppliedSeconds;
}
Vector2 acceleration = force / mass;
velocity += (acceleration * deltaTimeSeconds);
position += (velocity * deltaTimeSeconds);
// New! Update the rotational velocity as well
float32 rotationalAcceleration = torque / momentOfInertia;
rotationalVelocity += (rotationalAcceleration * deltaTimeSeconds);
rotation += (rotationalVelocity * deltaTimeSeconds);
for (int32 idx = 0; idx < numImpulses; idx++) {
if (activeImpulses[idx].isDead) {
for (int j = idx + 1; j < numImpulses; j++) {
activeImpulses[j - 1] = activeImpulses[j];
}
idx = idx - 1;
numImpulses--;
}
}
}
};
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