From 16cfdfec19145ac2b890e5a30ad4075092f06da8 Mon Sep 17 00:00:00 2001
From: elsid <elsid.mail@gmail.com>
Date: Thu, 3 Feb 2022 00:04:28 +0100
Subject: [PATCH] Avoid unnecessary computation

And fix UBSAN error:

/home/elsid/dev/openmw/apps/openmw/mwrender/renderingmanager.cpp:659:81: runtime error: division by zero
    #0 0x556eac16f4dc in MWRender::RenderingManager::configureAmbient(ESM::Cell const*) /home/elsid/dev/openmw/apps/openmw/mwrender/renderingmanager.cpp:659
    #1 0x556eadfd3d60 in MWWorld::Scene::loadCell(MWWorld::CellStore*, Loading::Listener*, bool, osg::Vec3f const&) /home/elsid/dev/openmw/apps/openmw/mwworld/scene.cpp:467
    #2 0x556eadfe3047 in MWWorld::Scene::changeToInteriorCell(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, ESM::Position const&, bool, bool) /home/elsid/dev/openmw/apps/openmw/mwworld/scene.cpp:830
    #3 0x556eadeb8fb3 in MWWorld::World::changeToInteriorCell(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, ESM::Position const&, bool, bool) /home/elsid/dev/openmw/apps/openmw/mwworld/worldimp.cpp:978
    #4 0x556eadeba5f1 in MWWorld::World::changeToCell(ESM::CellId const&, ESM::Position const&, bool, bool) /home/elsid/dev/openmw/apps/openmw/mwworld/worldimp.cpp:1008
    #5 0x556eaeb852dd in MWState::StateManager::loadGame(MWState::Character const*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) /home/elsid/dev/openmw/apps/openmw/mwstate/statemanagerimp.cpp:533
    #6 0x556eaeb81674 in MWState::StateManager::loadGame(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) /home/elsid/dev/openmw/apps/openmw/mwstate/statemanagerimp.cpp:366
    #7 0x556eaebd2aae in OMW::Engine::go() /home/elsid/dev/openmw/apps/openmw/engine.cpp:1025
    #8 0x556eaeba810a in runApplication(int, char**) /home/elsid/dev/openmw/apps/openmw/main.cpp:221
    #9 0x556eaf865e9a in wrapApplication(int (*)(int, char**), int, char**, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) /home/elsid/dev/openmw/components/debug/debugging.cpp:205
    #10 0x556eaeba8368 in main /home/elsid/dev/openmw/apps/openmw/main.cpp:233
    #11 0x7f89773b3b24 in __libc_start_main (/usr/lib/libc.so.6+0x27b24)
    #12 0x556eac13c09d in _start (/home/elsid/dev/openmw/build/gcc/ubsan/openmw+0x669c09d)
---
 apps/openmw/mwrender/renderingmanager.cpp | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/apps/openmw/mwrender/renderingmanager.cpp b/apps/openmw/mwrender/renderingmanager.cpp
index 6c9ff173ae..90fe0877ec 100644
--- a/apps/openmw/mwrender/renderingmanager.cpp
+++ b/apps/openmw/mwrender/renderingmanager.cpp
@@ -656,11 +656,10 @@ namespace MWRender
             if (relativeLuminance < mMinimumAmbientLuminance)
             {
                 // brighten ambient so it reaches the minimum threshold but no more, we want to mess with content data as least we can
-                float targetBrightnessIncreaseFactor = mMinimumAmbientLuminance / relativeLuminance;
                 if (ambient.r() == 0.f && ambient.g() == 0.f && ambient.b() == 0.f)
                     ambient = osg::Vec4(mMinimumAmbientLuminance, mMinimumAmbientLuminance, mMinimumAmbientLuminance, ambient.a());
                 else
-                    ambient *= targetBrightnessIncreaseFactor;
+                    ambient *= mMinimumAmbientLuminance / relativeLuminance;
             }
         }