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Fix RigidDynamicBody gaining momentum with bounce

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Bounce calculation now uses the previous frame's velocity, so it's
consistent with the actual motion of the bodies involved and not the
yet-to-be-applied forces.

When bounce is 1, using the current velocity was causing the new forces
(including gravity) to be taken into account, which lead to the bounce
velocity to be higher than the falling velocity at the moment of impact,
adding more and more energy over time.
This commit is contained in:
PouleyKetchoupp 2021-11-25 08:26:38 -07:00
parent b3ec5a16ea
commit 7032cf0637
6 changed files with 24 additions and 20 deletions
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3
servers/physics_2d/godot_body_2d.cpp
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@ -549,6 +549,9 @@ void GodotBody2D::integrate_forces(real_t p_step) {
gravity *= gravity_scale;
prev_linear_velocity = linear_velocity;
prev_angular_velocity = angular_velocity;
Vector2 motion;
bool do_motion = false;

6
servers/physics_2d/godot_body_2d.h
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@ -50,6 +50,9 @@ class GodotBody2D : public GodotCollisionObject2D {
Vector2 linear_velocity;
real_t angular_velocity = 0.0;
Vector2 prev_linear_velocity;
real_t prev_angular_velocity = 0.0;
Vector2 constant_linear_velocity;
real_t constant_angular_velocity = 0.0;
@ -209,6 +212,9 @@ public:
_FORCE_INLINE_ void set_angular_velocity(real_t p_velocity) { angular_velocity = p_velocity; }
_FORCE_INLINE_ real_t get_angular_velocity() const { return angular_velocity; }
_FORCE_INLINE_ Vector2 get_prev_linear_velocity() const { return prev_linear_velocity; }
_FORCE_INLINE_ real_t get_prev_angular_velocity() const { return prev_angular_velocity; }
_FORCE_INLINE_ void set_biased_linear_velocity(const Vector2 &p_velocity) { biased_linear_velocity = p_velocity; }
_FORCE_INLINE_ Vector2 get_biased_linear_velocity() const { return biased_linear_velocity; }

7
servers/physics_2d/godot_body_pair_2d.cpp
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@ -32,7 +32,6 @@
#include "godot_collision_solver_2d.h"
#include "godot_space_2d.h"
#define POSITION_CORRECTION
#define ACCUMULATE_IMPULSES
void GodotBodyPair2D::_add_contact(const Vector2 &p_point_A, const Vector2 &p_point_B, void *p_self) {
@ -453,9 +452,9 @@ bool GodotBodyPair2D::pre_solve(real_t p_step) {
c.bounce = combine_bounce(A, B);
if (c.bounce) {
Vector2 crA(-A->get_angular_velocity() * c.rA.y, A->get_angular_velocity() * c.rA.x);
Vector2 crB(-B->get_angular_velocity() * c.rB.y, B->get_angular_velocity() * c.rB.x);
Vector2 dv = B->get_linear_velocity() + crB - A->get_linear_velocity() - crA;
Vector2 crA(-A->get_prev_angular_velocity() * c.rA.y, A->get_prev_angular_velocity() * c.rA.x);
Vector2 crB(-B->get_prev_angular_velocity() * c.rB.y, B->get_prev_angular_velocity() * c.rB.x);
Vector2 dv = B->get_prev_linear_velocity() + crB - A->get_prev_linear_velocity() - crA;
c.bounce = c.bounce * dv.dot(c.normal);
}

3
servers/physics_3d/godot_body_3d.cpp
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@ -604,6 +604,9 @@ void GodotBody3D::integrate_forces(real_t p_step) {
gravity *= gravity_scale;
prev_linear_velocity = linear_velocity;
prev_angular_velocity = angular_velocity;
Vector3 motion;
bool do_motion = false;

6
servers/physics_3d/godot_body_3d.h
View File

@ -45,6 +45,9 @@ class GodotBody3D : public GodotCollisionObject3D {
Vector3 linear_velocity;
Vector3 angular_velocity;
Vector3 prev_linear_velocity;
Vector3 prev_angular_velocity;
Vector3 constant_linear_velocity;
Vector3 constant_angular_velocity;
@ -207,6 +210,9 @@ public:
_FORCE_INLINE_ void set_angular_velocity(const Vector3 &p_velocity) { angular_velocity = p_velocity; }
_FORCE_INLINE_ Vector3 get_angular_velocity() const { return angular_velocity; }
_FORCE_INLINE_ Vector3 get_prev_linear_velocity() const { return prev_linear_velocity; }
_FORCE_INLINE_ Vector3 get_prev_angular_velocity() const { return prev_angular_velocity; }
_FORCE_INLINE_ const Vector3 &get_biased_linear_velocity() const { return biased_linear_velocity; }
_FORCE_INLINE_ const Vector3 &get_biased_angular_velocity() const { return biased_angular_velocity; }

19
servers/physics_3d/godot_body_pair_3d.cpp
View File

@ -35,18 +35,6 @@
#include "core/os/os.h"
/*
#define NO_ACCUMULATE_IMPULSES
#define NO_SPLIT_IMPULSES
#define NO_FRICTION
*/
#define NO_TANGENTIALS
/* BODY PAIR */
//#define ALLOWED_PENETRATION 0.01
#define RELAXATION_TIMESTEPS 3
#define MIN_VELOCITY 0.0001
#define MAX_BIAS_ROTATION (Math_PI / 8)
@ -370,10 +358,9 @@ bool GodotBodyPair3D::pre_solve(real_t p_step) {
c.bounce = combine_bounce(A, B);
if (c.bounce) {
Vector3 crA = A->get_angular_velocity().cross(c.rA);
Vector3 crB = B->get_angular_velocity().cross(c.rB);
Vector3 dv = B->get_linear_velocity() + crB - A->get_linear_velocity() - crA;
//normal impule
Vector3 crA = A->get_prev_angular_velocity().cross(c.rA);
Vector3 crB = B->get_prev_angular_velocity().cross(c.rB);
Vector3 dv = B->get_prev_linear_velocity() + crB - A->get_prev_linear_velocity() - crA;
c.bounce = c.bounce * dv.dot(c.normal);
}
}