From 7d09a7957c2b778c5d7a5d989ca7510d13c58a31 Mon Sep 17 00:00:00 2001
From: MihailRis <mexaruc@gmail.com>
Date: Fri, 6 Mar 2026 19:47:43 +0300
Subject: [PATCH] fix division by zero in some cases

---
 src/objects/Entities.cpp      | 26 +++++++++++++++++---------
 src/physics/PhysicsSolver.cpp |  9 +++++++--
 2 files changed, 24 insertions(+), 11 deletions(-)

diff --git a/src/objects/Entities.cpp b/src/objects/Entities.cpp
index 6750116df..17b5acd83 100644
--- a/src/objects/Entities.cpp
+++ b/src/objects/Entities.cpp
@@ -1,28 +1,29 @@
 #define VC_ENABLE_REFLECTION
 #include "Entities.hpp"
 
-#include <entt/entity/registry.hpp>
-#include <glm/ext/matrix_transform.hpp>
-#include <sstream>
-
 #include "assets/Assets.hpp"
 #include "content/Content.hpp"
 #include "data/dv_util.hpp"
 #include "debug/Logger.hpp"
 #include "engine/Engine.hpp"
+#include "Entity.hpp"
+#include "EntityDef.hpp"
+#include "graphics/commons/Model.hpp"
 #include "graphics/core/DrawContext.hpp"
 #include "graphics/core/LineBatch.hpp"
-#include "graphics/commons/Model.hpp"
 #include "graphics/render/ModelBatch.hpp"
 #include "logic/scripting/scripting.hpp"
 #include "maths/FrustumCulling.hpp"
 #include "maths/rays.hpp"
-#include "EntityDef.hpp"
-#include "Entity.hpp"
-#include "rigging.hpp"
+#include "maths/util.hpp"
 #include "physics/PhysicsSolver.hpp"
+#include "rigging.hpp"
 #include "world/Level.hpp"
 
+#include <entt/entity/registry.hpp>
+#include <glm/ext/matrix_transform.hpp>
+#include <sstream>
+
 static debug::Logger logger("entities");
 
 Entities::Entities(Level& level)
@@ -336,7 +337,14 @@ void Entities::updatePhysics(float delta) {
                                 ? 8.0f
                                 : (!grounded ? 2.0f : 10.0f);
             hitbox.scale = transform.size;
-            transform.setPos(hitbox.position);
+            if (util::is_nan_or_inf(hitbox.position)) {
+                logger.error()
+                    << "something bad happened in physics engine (entity "
+                    << eid.def.name << "#" << eid.uid << ")";
+                hitbox.position = transform.pos;
+            } else {
+                transform.setPos(hitbox.position);
+            }
             if (hitbox.grounded && !grounded) {
                 scripting::on_entity_grounded(
                     *get(eid.uid), glm::length(prevVel - hitbox.velocity)
diff --git a/src/physics/PhysicsSolver.cpp b/src/physics/PhysicsSolver.cpp
index bf78f860a..f9e4b6e23 100644
--- a/src/physics/PhysicsSolver.cpp
+++ b/src/physics/PhysicsSolver.cpp
@@ -140,8 +140,10 @@ static bool calc_collision_neg_y(
             if (pos.y < newy && glm::abs(pos.y - newy) < 0.5f) {
                 pos.y = newy;
             }
-            hitbox.groundVelocity =
-                (box->position - box->prevPosition) / box->delta;
+            if (glm::abs(box->delta) > 1e-5f) {
+                hitbox.groundVelocity =
+                    (box->position - box->prevPosition) / box->delta;
+            }
             if (vel.y < 0.0f) {
                 vel.y = 0.0f;
                 if (hitbox.groundMaterial.empty()) {
@@ -300,6 +302,9 @@ void PhysicsSolver::calcSubstep(
 ) {
     if (hitbox.grounded) {
         pos.x += hitbox.groundVelocity.x * dt * substeps;
+        if (hitbox.groundVelocity.y < 0.0f) {
+            pos.y += hitbox.groundVelocity.y * dt * substeps;
+        }
         pos.z += hitbox.groundVelocity.z * dt * substeps;
     }