SoftBody3D: Add a property for scaling rest lengths of edge constraints

modules/jolt_physics/jolt_physics_server_3d.cpp

@@ -1126,6 +1126,20 @@ real_t JoltPhysicsServer3D::soft_body_get_linear_stiffness(RID p_body) const {
 	return (real_t)body->get_stiffness_coefficient();
 }
 
+void JoltPhysicsServer3D::soft_body_set_shrinking_factor(RID p_body, real_t p_shrinking_factor) {
+	JoltSoftBody3D *body = soft_body_owner.get_or_null(p_body);
+	ERR_FAIL_NULL(body);
+
+	return body->set_shrinking_factor((float)p_shrinking_factor);
+}
+
+real_t JoltPhysicsServer3D::soft_body_get_shrinking_factor(RID p_body) const {
+	JoltSoftBody3D *body = soft_body_owner.get_or_null(p_body);
+	ERR_FAIL_NULL_V(body, 0.0);
+
+	return (real_t)body->get_shrinking_factor();
+}
+
 void JoltPhysicsServer3D::soft_body_set_pressure_coefficient(RID p_body, real_t p_coefficient) {
 	JoltSoftBody3D *body = soft_body_owner.get_or_null(p_body);
 	ERR_FAIL_NULL(body);

modules/jolt_physics/jolt_physics_server_3d.h

@@ -331,6 +331,9 @@ public:
 	virtual void soft_body_set_linear_stiffness(RID p_body, real_t p_coefficient) override;
 	virtual real_t soft_body_get_linear_stiffness(RID p_body) const override;
 
+	virtual void soft_body_set_shrinking_factor(RID p_body, real_t p_shrinking_factor) override;
+	virtual real_t soft_body_get_shrinking_factor(RID p_body) const override;
+
 	virtual void soft_body_set_pressure_coefficient(RID p_body, real_t p_coefficient) override;
 	virtual real_t soft_body_get_pressure_coefficient(RID p_body) const override;
 

modules/jolt_physics/objects/jolt_soft_body_3d.cpp

@@ -202,6 +202,10 @@ bool JoltSoftBody3D::_ref_shared_data() {
 		vertex_attrib.mCompliance = vertex_attrib.mShearCompliance = inverse_stiffness;
 
 		settings.CreateConstraints(&vertex_attrib, 1, JPH::SoftBodySharedSettings::EBendType::None);
+		float multiplier = 1.0f - shrinking_factor;
+		for (JPH::SoftBodySharedSettings::Edge &e : settings.mEdgeConstraints) {
+			e.mRestLength *= multiplier;
+		}
 		settings.Optimize();
 	} else {
 		iter_shared_data->value.ref_count++;
@@ -454,6 +458,14 @@ void JoltSoftBody3D::set_stiffness_coefficient(float p_coefficient) {
 	stiffness_coefficient = CLAMP(p_coefficient, 0.0f, 1.0f);
 }
 
+float JoltSoftBody3D::get_shrinking_factor() const {
+	return shrinking_factor;
+}
+
+void JoltSoftBody3D::set_shrinking_factor(float p_shrinking_factor) {
+	shrinking_factor = p_shrinking_factor;
+}
+
 void JoltSoftBody3D::set_pressure(float p_pressure) {
 	if (unlikely(pressure == p_pressure)) {
 		return;

modules/jolt_physics/objects/jolt_soft_body_3d.h

@@ -64,6 +64,7 @@ class JoltSoftBody3D final : public JoltObject3D {
 	float pressure = 0.0f;
 	float linear_damping = 0.01f;
 	float stiffness_coefficient = 0.5f;
+	float shrinking_factor = 0.0f;
 
 	int simulation_precision = 5;
 
@@ -138,6 +139,9 @@ public:
 	float get_stiffness_coefficient() const;
 	void set_stiffness_coefficient(float p_coefficient);
 
+	float get_shrinking_factor() const;
+	void set_shrinking_factor(float p_shrinking_factor);
+
 	float get_pressure() const { return pressure; }
 	void set_pressure(float p_pressure);