From 5d18933411a91987b1a380e38229d064ed22a3dd Mon Sep 17 00:00:00 2001
From: Josip Miskovic <josipmiskovic@gmail.com>
Date: Wed, 3 Jun 2020 20:13:13 +0300
Subject: [PATCH] Limit simulation parameters to positive values

---
 src/api/l_physics_joints.c | 4 ++++
 src/api/l_physics_world.c  | 2 ++
 2 files changed, 6 insertions(+)

diff --git a/src/api/l_physics_joints.c b/src/api/l_physics_joints.c
index 176c4ce0..5bdddd8f 100644
--- a/src/api/l_physics_joints.c
+++ b/src/api/l_physics_joints.c
@@ -132,6 +132,7 @@ static int l_lovrBallJointGetResponseTime(lua_State* L) {
 static int l_lovrBallJointSetResponseTime(lua_State* L) {
   Joint* joint = luax_checkjoint(L, 1);
   float responseTime = luax_checkfloat(L, 2);
+  lovrAssert(responseTime >= 0, "Negative response time causes simulation instability");
   lovrBallJointSetResponseTime(joint, responseTime);
   return 0;
 }
@@ -146,6 +147,7 @@ static int l_lovrBallJointGetTightness(lua_State* L) {
 static int l_lovrBallJointSetTightness(lua_State* L) {
   Joint* joint = luax_checkjoint(L, 1);
   float tightness = luax_checkfloat(L, 2);
+  lovrAssert(tightness >= 0, "Negative tightness factor causes simulation instability");
   lovrBallJointSetTightness(joint, tightness);
   return 0;
 }
@@ -206,6 +208,7 @@ static int l_lovrDistanceJointGetResponseTime(lua_State* L) {
 static int l_lovrDistanceJointSetResponseTime(lua_State* L) {
   Joint* joint = luax_checkjoint(L, 1);
   float responseTime = luax_checkfloat(L, 2);
+  lovrAssert(responseTime >= 0, "Negative response time causes simulation instability");
   lovrDistanceJointSetResponseTime(joint, responseTime);
   return 0;
 }
@@ -220,6 +223,7 @@ static int l_lovrDistanceJointGetTightness(lua_State* L) {
 static int l_lovrDistanceJointSetTightness(lua_State* L) {
   Joint* joint = luax_checkjoint(L, 1);
   float tightness = luax_checkfloat(L, 2);
+  lovrAssert(tightness >= 0, "Negative tightness factor causes simulation instability");
   lovrDistanceJointSetTightness(joint, tightness);
   return 0;
 }
diff --git a/src/api/l_physics_world.c b/src/api/l_physics_world.c
index f87f8208..1d2b5ffa 100644
--- a/src/api/l_physics_world.c
+++ b/src/api/l_physics_world.c
@@ -190,6 +190,7 @@ static int l_lovrWorldSetGravity(lua_State* L) {
 static int l_lovrWorldGetTightness(lua_State* L) {
   World* world = luax_checktype(L, 1, World);
   float tightness = lovrWorldGetTightness(world);
+  lovrAssert(tightness >= 0, "Negative tightness factor causes simulation instability");
   lua_pushnumber(L, tightness);
   return 1;
 }
@@ -211,6 +212,7 @@ static int l_lovrWorldGetResponseTime(lua_State* L) {
 static int l_lovrWorldSetResponseTime(lua_State* L) {
   World* world = luax_checktype(L, 1, World);
   float responseTime = luax_checkfloat(L, 2);
+  lovrAssert(responseTime >= 0, "Negative response time causes simulation instability");
   lovrWorldSetResponseTime(world, responseTime);
   return 0;
 }