Noniv · Sep 21, 2026
diff --git a/src/mods/UObjectHook.cpp b/src/mods/UObjectHook.cpp
@@ -612,7 +612,8 @@ void UObjectHook::on_pre_calculate_stereo_view_offset(void* stereo_device, const
         } // else todo?
     }
 
-    if ((view_index + 1) % 2 == 0) {
+    // Mono only has a single view pass, so there is no second view to wait for
+    if ((view_index + 1) % 2 == 0 || VR::get()->is_using_mono()) {
         tick_attachments(view_rotation, world_to_meters, view_location, is_double);
     }
 }

diff --git a/src/mods/VR.cpp b/src/mods/VR.cpp
@@ -1561,7 +1561,7 @@ void VR::update_hmd_state(bool from_view_extensions, uint32_t frame_count) {
         }
     }
 
-    if (frame_count != 0 && is_using_afr() && frame_count % 2 == 0) {
+    if (frame_count != 0 && is_using_alternating_eyes() && frame_count % 2 == 0) {
         if (runtime->is_openxr()) {
             std::scoped_lock __{ m_openxr->sync_assignment_mtx };
 
@@ -2060,7 +2060,7 @@ void VR::on_present() {
     m_present_thread_id = GetCurrentThreadId();
 
     utility::ScopeGuard _guard {[&]() {
-        if (!is_using_afr() || (m_render_frame_count + 1) % 2 == m_left_eye_interval) {
+        if (!is_using_alternating_eyes() || (m_render_frame_count + 1) % 2 == m_left_eye_interval) {
             SetEvent(m_present_finished_event);
         }
 
@@ -2069,7 +2069,7 @@ void VR::on_present() {
 
     m_frame_count = get_runtime()->internal_render_frame_count;
 
-    if (!is_using_afr() || m_render_frame_count % 2 == m_left_eye_interval) {
+    if (!is_using_alternating_eyes() || m_render_frame_count % 2 == m_left_eye_interval) {
         ResetEvent(m_present_finished_event);
     }
 
@@ -2126,7 +2126,7 @@ void VR::on_present() {
     const auto renderer = g_framework->get_renderer_type();
     vr::EVRCompositorError e = vr::EVRCompositorError::VRCompositorError_None;
 
-    const auto is_left_eye_frame = is_using_afr() ? (m_render_frame_count % 2 == m_left_eye_interval) : true;
+    const auto is_left_eye_frame = is_using_alternating_eyes() ? (m_render_frame_count % 2 == m_left_eye_interval) : true;
 
     if (is_left_eye_frame && get_synchronize_stage() == VR::SynchronizeStage::LATE) {
         const auto had_sync = runtime->got_first_sync;
@@ -2217,7 +2217,7 @@ void VR::on_post_present() {
 
     detect_controllers();
 
-    const auto is_left_eye_frame = is_using_afr() ? (is_same_frame || (m_render_frame_count % 2 == m_left_eye_interval)) : true;
+    const auto is_left_eye_frame = is_using_alternating_eyes() ? (is_same_frame || (m_render_frame_count % 2 == m_left_eye_interval)) : true;
 
     if (is_left_eye_frame) {
         if (get_synchronize_stage() == VR::SynchronizeStage::VERY_LATE || !runtime->got_first_sync) {
@@ -2411,7 +2411,11 @@ void VR::on_draw_sidebar_entry(std::string_view name) {
     }
 
     if (selected_page == PAGE_UNREAL) {
-        m_rendering_method->draw("Rendering Method");
+        if (m_rendering_method->draw("Rendering Method")) {
+            // Mono forces its own projection overrides, so the eye projections need to be regenerated when switching.
+            get_runtime()->should_recalculate_eye_projections = true;
+        }
+
         m_synced_afr_method->draw("Synced Sequential Method");
 
         m_world_scale->draw("World Scale");

diff --git a/src/mods/VR.hpp b/src/mods/VR.hpp
@@ -29,6 +29,7 @@ class VR : public Mod {
         NATIVE_STEREO = 0,
         SYNCHRONIZED = 1,
         ALTERNATING = 2,
+        MONO = 3,
     };
 
     enum SynchronizeStage {
@@ -408,9 +409,22 @@ class VR : public Mod {
     bool is_using_afr() const {
         return m_rendering_method->value() == RenderingMethod::ALTERNATING || 
                m_rendering_method->value() == RenderingMethod::SYNCHRONIZED ||
+               m_rendering_method->value() == RenderingMethod::MONO ||
                m_extreme_compat_mode->value() == true;
     }
 
+    // Mono renders a single centered view every frame and submits it to both eyes.
+    // It shares the single view/single wide render target layout with AFR (is_using_afr() is true)
+    // but does not alternate eyes between frames.
+    bool is_using_mono() const {
+        return m_rendering_method->value() == RenderingMethod::MONO;
+    }
+
+    // Whether the left and right eyes are rendered on separate (alternating) frames.
+    bool is_using_alternating_eyes() const {
+        return is_using_afr() && !is_using_mono();
+    }
+
     bool is_using_synchronized_afr() const {
         return m_rendering_method->value() == RenderingMethod::SYNCHRONIZED ||
                (m_extreme_compat_mode->value() && m_rendering_method->value() == RenderingMethod::NATIVE_STEREO);
@@ -624,11 +638,20 @@ class VR : public Mod {
         return m_extreme_compat_mode->value();
     }
 
-    auto get_horizontal_projection_override() const {
+    // Mono needs both eyes to share the exact same frustum, the per-eye view bounds then crop the shared image.
+    int32_t get_horizontal_projection_override() const {
+        if (is_using_mono()) {
+            return HORIZONTAL_PROJECTION_OVERRIDE::HORIZONTAL_SYMMETRIC;
+        }
+
         return m_horizontal_projection_override->value();
     }
 
-    auto get_vertical_projection_override() const {
+    int32_t get_vertical_projection_override() const {
+        if (is_using_mono() && m_vertical_projection_override->value() == VERTICAL_PROJECTION_OVERRIDE::VERTICAL_DEFAULT) {
+            return VERTICAL_PROJECTION_OVERRIDE::VERTICAL_MATCHED;
+        }
+
         return m_vertical_projection_override->value();
     }
 
@@ -837,6 +860,7 @@ class VR : public Mod {
         "Native Stereo",
         "Synchronized Sequential",
         "Alternating/AFR",
+        "Mono",
     };
 
     static const inline std::vector<std::string> s_sync_mode_names{

diff --git a/src/mods/vr/D3D11Component.cpp b/src/mods/vr/D3D11Component.cpp
@@ -259,8 +259,10 @@ vr::EVRCompositorError D3D11Component::on_frame(VR* vr) {
     const auto is_same_frame = m_last_rendered_frame > 0 && m_last_rendered_frame == vr->m_render_frame_count;
     m_last_rendered_frame = vr->m_render_frame_count;
 
+    // Mono uses the AFR texture layout, but every frame is submitted to both eyes (like the is_same_frame case)
+    const auto is_mono = vr->is_using_mono();
     const auto is_actually_afr = vr->is_using_afr();
-    const auto is_afr = !is_same_frame && vr->is_using_afr();
+    const auto is_afr = !is_same_frame && vr->is_using_alternating_eyes();
     const auto is_left_eye_frame = is_afr && vr->m_render_frame_count % 2 == vr->m_left_eye_interval;
     const auto is_right_eye_frame = !is_afr || vr->m_render_frame_count % 2 == vr->m_right_eye_interval;
 
@@ -423,7 +425,14 @@ vr::EVRCompositorError D3D11Component::on_frame(VR* vr) {
 
         if (!is_afr) {
             // Render right side to right screen tex
-            if (m_scene_capture_tex_ref.has_texture() && m_scene_capture_tex_ref.has_srv()) {
+            if (is_mono) {
+                render_srv_to_rtv(
+                    m_game_batch.get(),
+                    m_engine_tex_ref,
+                    m_2d_screen_tex[1],
+                    RECT{0, 0, (LONG)((float)m_backbuffer_size[0] / 2.0f), (LONG)m_backbuffer_size[1]}
+                );
+            } else if (m_scene_capture_tex_ref.has_texture() && m_scene_capture_tex_ref.has_srv()) {
                 render_srv_to_rtv(
                     m_game_batch.get(),
                     m_scene_capture_tex_ref,
@@ -630,7 +639,7 @@ vr::EVRCompositorError D3D11Component::on_frame(VR* vr) {
             if (is_actually_afr) {
                 D3D11_BOX src_box{};
                 if (!vr->is_extreme_compatibility_mode_enabled()) {
-                    if (!is_afr) {
+                    if (!is_afr && !is_mono) {
                         src_box.left = m_backbuffer_size[0] / 2;
                         src_box.right = m_backbuffer_size[0];
                         src_box.top = 0;
@@ -770,7 +779,7 @@ vr::EVRCompositorError D3D11Component::on_frame(VR* vr) {
             if (!m_scene_capture_tex_ref.has_texture()) {
                 D3D11_BOX src_box{};
                 if (!vr->is_extreme_compatibility_mode_enabled()) {
-                    if (!is_afr) {
+                    if (!is_afr && !is_mono) {
                         src_box.left = m_backbuffer_size[0] / 2;
                         src_box.right = m_backbuffer_size[0];
                         src_box.top = 0;

diff --git a/src/mods/vr/D3D12Component.cpp b/src/mods/vr/D3D12Component.cpp
@@ -79,8 +79,10 @@ vr::EVRCompositorError D3D12Component::on_frame(VR* vr) {
     const auto is_same_frame = m_last_rendered_frame > 0 && m_last_rendered_frame == vr->m_render_frame_count;
     m_last_rendered_frame = vr->m_render_frame_count;
 
+    // Mono uses the AFR texture layout, but every frame is submitted to both eyes (like the is_same_frame case)
+    const auto is_mono = vr->is_using_mono();
     const auto is_actually_afr = vr->is_using_afr();
-    const auto is_afr = !is_same_frame && vr->is_using_afr();
+    const auto is_afr = !is_same_frame && vr->is_using_alternating_eyes();
     const auto is_left_eye_frame = is_afr && vr->m_render_frame_count % 2 == vr->m_left_eye_interval;
     const auto is_right_eye_frame = !is_afr || vr->m_render_frame_count % 2 == vr->m_right_eye_interval;
 
@@ -307,7 +309,17 @@ vr::EVRCompositorError D3D12Component::on_frame(VR* vr) {
 
             if (!is_afr) {
                 // Render right side to right screen tex
-                if (m_scene_capture_tex.texture.Get() != nullptr) {
+                if (is_mono) {
+                    d3d12::render_srv_to_rtv(
+                        m_game_batch.get(),
+                        commands.cmd_list.Get(),
+                        m_game_tex,
+                        m_2d_screen_tex[1],
+                        RECT{0, 0, (LONG)((float)m_backbuffer_size[0] / 2.0f), (LONG)m_backbuffer_size[1]},
+                        ENGINE_SRC_COLOR,
+                        ENGINE_SRC_COLOR
+                    );
+                } else if (m_scene_capture_tex.texture.Get() != nullptr) {
                     d3d12::render_srv_to_rtv(
                         m_game_batch.get(),
                         commands.cmd_list.Get(),
@@ -519,7 +531,7 @@ vr::EVRCompositorError D3D12Component::on_frame(VR* vr) {
                 D3D12_BOX src_box{};
 
                 if (!vr->is_extreme_compatibility_mode_enabled()) {
-                    if (!is_afr) {
+                    if (!is_afr && !is_mono) {
                         src_box.left = m_backbuffer_size[0] / 2;
                         src_box.right = m_backbuffer_size[0];
                         src_box.top = 0;
@@ -591,7 +603,7 @@ vr::EVRCompositorError D3D12Component::on_frame(VR* vr) {
                 }
             }
 
-            if (!is_afr) {
+            if (!is_afr && !is_mono) {
                 if (m_scene_capture_tex.texture.Get() == nullptr) {
                     m_openvr.copy_right(backbuffer.Get(), D3D12_RESOURCE_STATE_RENDER_TARGET);
                 } else {

diff --git a/src/mods/vr/FFakeStereoRenderingHook.cpp b/src/mods/vr/FFakeStereoRenderingHook.cpp
@@ -3066,7 +3066,7 @@ sdk::FSceneView* FFakeStereoRenderingHook::sceneview_constructor(sdk::FSceneView
 
     last_frame_count = g_frame_count;
 
-    const auto true_index = vr->is_using_afr() ? (g_frame_count + last_index) % 2 : last_index;
+    const auto true_index = vr->is_using_alternating_eyes() ? (g_frame_count + last_index) % 2 : (vr->is_using_mono() ? 0 : last_index);
 
     if (vr->is_splitscreen_compatibility_enabled() || vr->is_sceneview_compatibility_enabled()) {
         int32_t w = vr->get_hmd_width();
@@ -3177,7 +3177,7 @@ sdk::FSceneView* FFakeStereoRenderingHook::sceneview_constructor(sdk::FSceneView
         }
     }
 
-    if (init_options_scene_state != nullptr && !new_scene_state_inserted_this_frame && vr->is_ghosting_fix_enabled() && !known_scene_states.empty() && vr->is_using_afr() && true_index == 1) {
+    if (init_options_scene_state != nullptr && !new_scene_state_inserted_this_frame && vr->is_ghosting_fix_enabled() && !known_scene_states.empty() && vr->is_using_alternating_eyes() && true_index == 1) {
         init_options->set_stereo_pass(EStereoscopicPass::eSSP_PRIMARY);
 
         // Set the scene state to the one that isn't the current one
@@ -3507,7 +3507,7 @@ void FFakeStereoRenderingHook::begin_render_viewfamily(ISceneViewExtension* exte
             int32_t x = 0;
             int32_t y = 0;
 
-            const auto true_index = vr->is_using_afr() ? (frame_count + 1) % 2 : view_index;
+            const auto true_index = vr->is_using_alternating_eyes() ? (frame_count + 1) % 2 : (vr->is_using_mono() ? 0 : view_index);
 
             if (!vr->is_using_afr() && true_index == 1) {
                 x += w;
@@ -4790,10 +4790,12 @@ __forceinline void FFakeStereoRenderingHook::calculate_stereo_view_offset(
     const auto has_double_precision = g_hook->m_has_double_precision;
     const auto rot_d = (Rotator<double>*)view_rotation;
 
+    const auto is_mono = vr->is_using_mono();
+
     if (vr->is_using_afr() && !is_full_pass) {
-        true_index = g_frame_count % 2;
+        true_index = is_mono ? 0 : g_frame_count % 2;
 
-        if (!vr->is_using_synchronized_afr()) {
+        if (!vr->is_using_synchronized_afr() && !is_mono) {
             if (g_hook->m_has_double_precision) {
                 if (true_index == 1) {
                     *rot_d = g_hook->m_last_afr_rotation_double;
@@ -4810,6 +4812,9 @@ __forceinline void FFakeStereoRenderingHook::calculate_stereo_view_offset(
         }
     }
 
+    // Mono only has a single pass per frame, so it has to act as both the first (left) and the last (right) eye pass.
+    const auto is_last_eye_pass = true_index == 1 || (is_mono && !is_full_pass);
+
     if (true_index == 0 && !is_full_pass) {
         if (has_double_precision) {
             g_hook->m_last_pre_rotation_double = *rot_d;
@@ -4927,7 +4932,10 @@ __forceinline void FFakeStereoRenderingHook::calculate_stereo_view_offset(
         const auto current_eye_rotation_offset = glm::normalize(glm::quat{vr->get_eye_transform(true_index)});
 
         const auto new_rotation = glm::normalize(vqi_norm * current_hmd_rotation * current_eye_rotation_offset);
-        const auto eye_offset = glm::vec3{vr->get_eye_offset((VRRuntime::Eye)(true_index))};
+        // Mono renders from the point directly between the eyes.
+        const auto eye_offset = is_mono ?
+            (glm::vec3{vr->get_eye_offset(VRRuntime::Eye::LEFT)} + glm::vec3{vr->get_eye_offset(VRRuntime::Eye::RIGHT)}) * 0.5f :
+            glm::vec3{vr->get_eye_offset((VRRuntime::Eye)(true_index))};
 
 
         const auto standing_delta = vr->get_position(0) - vr->get_standing_origin();
@@ -4971,7 +4979,7 @@ __forceinline void FFakeStereoRenderingHook::calculate_stereo_view_offset(
         // Roomscale movement
         // only do it on the right eye pass
         // if we did it on the left, there would be eye desyncs when the right eye is rendered
-        if (true_index == 1 && (vr->is_roomscale_enabled() || vr->is_aim_pawn_control_rotation_enabled())) {
+        if (is_last_eye_pass && (vr->is_roomscale_enabled() || vr->is_aim_pawn_control_rotation_enabled())) {
             const auto world = sdk::UEngine::get()->get_world();
 
             if (const auto controller = sdk::UGameplayStatics::get()->get_player_controller(world, 0); controller != nullptr) {
@@ -5040,7 +5048,7 @@ __forceinline void FFakeStereoRenderingHook::calculate_stereo_view_offset(
         }
 
         // Modify Player Control Rotation
-        if (true_index == 1 && vr->is_aim_modify_player_control_rotation_enabled() && vr->is_any_aim_method_active()) {
+        if (is_last_eye_pass && vr->is_aim_modify_player_control_rotation_enabled() && vr->is_any_aim_method_active()) {
             if (g_hook->m_tracking_system_hook != nullptr) {
                 g_hook->m_tracking_system_hook->manual_update_control_rotation();
             }
@@ -5166,7 +5174,7 @@ __forceinline Matrix4x4f* FFakeStereoRenderingHook::calculate_stereo_projection_
         auto true_index = index_starts_from_one ? ((view_index + 1) % 2) : (view_index % 2);
 
         if (vr->is_using_afr()) {
-            true_index = g_frame_count % 2;
+            true_index = vr->is_using_mono() ? 0 : g_frame_count % 2;
         }
 
         auto& double_matrix = *(Matrix4x4d*)out;
@@ -5352,7 +5360,7 @@ uint32_t FFakeStereoRenderingHook::get_desired_number_of_views_hook(FFakeStereoR
     if (!is_stereo_enabled || (vr->is_using_afr() && !vr->is_splitscreen_compatibility_enabled())) {
         // We need to know about the second scene state to fix ghosting, so set the view count to 2
         // after we know about it, we can continue returning 1.
-        if (is_stereo_enabled && vr->is_ghosting_fix_enabled() && vr->is_using_afr() &&
+        if (is_stereo_enabled && vr->is_ghosting_fix_enabled() && vr->is_using_alternating_eyes() &&
             g_hook->m_sceneview_data.known_scene_states.size() < 2 && g_hook->m_fixed_localplayer_view_count &&
             !!g_hook->m_sceneview_data.constructor_hook && g_hook->m_has_view_extensions_installed)
         {

diff --git a/src/mods/vr/OverlayComponent.cpp b/src/mods/vr/OverlayComponent.cpp
@@ -97,7 +97,7 @@ void OverlayComponent::update_input_mouse_emulation() {
     if (m_framework_intersect_state.intersecting && VR::get()->is_using_controllers()) {
         auto vr = VR::get();
         auto& io = ImGui::GetIO();
-        const auto is_initial_frame = !vr->is_using_afr() || vr->get_frame_count() % 2 == vr->m_left_eye_interval;
+        const auto is_initial_frame = !vr->is_using_alternating_eyes() || vr->get_frame_count() % 2 == vr->m_left_eye_interval;
 
         const auto x = m_framework_intersect_state.swapchain_intersection_point.x;
         const auto y = m_framework_intersect_state.swapchain_intersection_point.y;
@@ -249,7 +249,7 @@ void OverlayComponent::update_input_openvr() {
 
     auto vr = VR::get();
     auto& io = ImGui::GetIO();
-    const auto is_initial_frame = !vr->is_using_afr() || vr->get_frame_count() % 2 == vr->m_left_eye_interval;
+    const auto is_initial_frame = !vr->is_using_alternating_eyes() || vr->get_frame_count() % 2 == vr->m_left_eye_interval;
 
     // Restore the previous frame's input state
     memcpy(io.KeysDown, m_initial_imgui_input_state.KeysDown, sizeof(io.KeysDown));

diff --git a/src/mods/vr/runtimes/OpenXR.cpp b/src/mods/vr/runtimes/OpenXR.cpp
@@ -168,7 +168,7 @@ VRRuntime::Error OpenXR::synchronize_frame(std::optional<uint32_t> frame_count)
             this->pipeline_states[next_frame].frame_state = this->frame_state;
             this->pipeline_states[next_frame].prev_frame_count = this->last_submit_state.frame_count;
 
-            if (VR::get()->is_using_afr()) {
+            if (VR::get()->is_using_alternating_eyes()) {
                 const auto afr_frame = (next_frame + 1) % OpenXR::QUEUE_SIZE;
                 this->pipeline_states[afr_frame].frame_state = this->frame_state;
                 this->pipeline_states[afr_frame].prev_frame_count = next_frame;
@@ -177,7 +177,7 @@ VRRuntime::Error OpenXR::synchronize_frame(std::optional<uint32_t> frame_count)
             this->pipeline_states[*frame_count % OpenXR::QUEUE_SIZE].frame_state = this->frame_state;
             this->pipeline_states[*frame_count % OpenXR::QUEUE_SIZE].prev_frame_count = *frame_count;
 
-            if (VR::get()->is_using_afr()) {
+            if (VR::get()->is_using_alternating_eyes()) {
                 this->pipeline_states[(*frame_count + 1) % OpenXR::QUEUE_SIZE].frame_state = this->frame_state;
                 this->pipeline_states[(*frame_count + 1) % OpenXR::QUEUE_SIZE].prev_frame_count = *frame_count;
             }