ImGui frame profiler overlay, and Vulkan per-draw descriptor set churn fix

code/CMakeLists.txt

@@ -77,6 +77,7 @@ TARGET_LINK_LIBRARIES(code PUBLIC jansson)
 target_link_libraries(code PUBLIC anl)
 
 target_link_libraries(code PUBLIC imgui)
+target_link_libraries(code PUBLIC implot)
 
 IF(FSO_BUILD_WITH_OPENXR)
 	target_link_libraries(code PUBLIC OpenXR::openxr_loader)

code/cmdline/cmdline.cpp

@@ -2339,10 +2339,9 @@ bool SetCmdlineParams()
 	if (gr_sync_validation_arg.found()) {
 		// Enables the Vulkan validation layer + debug messenger + synchronization
 		// validation feature (see VulkanRenderer::initializeInstance), but NOT the
-		// engine-level graphics debug output: -gr_debug additionally draws debug
-		// overlays (e.g. output_uniform_debug_data), which are unrelated to GPU
-		// sync validation and would otherwise appear as spurious on-screen
-		// artifacts. Keep this a pure GPU-validation switch.
+		// engine-level graphics debug output: -gr_debug additionally feeds extra
+		// stat groups into the ImGui frame profiler overlay (see gr_get_debug_stats),
+		// which are unrelated to GPU sync validation. Keep this a pure GPU-validation switch.
 		Cmdline_gr_sync_validation = true;
 	}
 

code/graphics/2d.cpp

@@ -22,6 +22,7 @@
 #include "material.h"
 #include "matrix.h"
 
+#include "bmpman/bmpman.h"
 #include "cmdline/cmdline.h"
 #include "debugconsole/console.h"
 #include "executor/global_executors.h"
@@ -42,6 +43,7 @@
 #include "render/3d.h"
 #include "scripting/hook_api.h"
 #include "scripting/scripting.h"
+#include "tracing/ProfilerOverlay.h"
 #include "tracing/tracing.h"
 #include "utils/boost/hash_combine.h"
 #include "utils/string_utils.h"
@@ -3170,24 +3172,38 @@ void gr_set_bitmap(int bitmap_num, int alphablend_mode, int bitblt_mode, float a
 	gr_screen.current_bitmap          = bitmap_num;
 }
 
-static void output_uniform_debug_data()
+gr_debug_stats gr_get_debug_stats()
 {
-	if (gr_screen.mode == GraphicsAPI::Stub) {
-		return;
+	gr_debug_stats stats;
+
+	if (!Cmdline_graphics_debug_output) {
+		return stats;
 	}
 
-	int line_height = gr_get_font_height() + 1;
+	if (UniformBufferManager) {
+		stats.uniform_buffer_valid = true;
+		stats.uniform_buffer_size = UniformBufferManager->getBufferSize();
+		stats.uniform_buffer_used = UniformBufferManager->getCurrentlyUsedSize();
+	}
 
-	gr_set_color_fast(&Color_bright_white);
+	gr_screen.gf_get_debug_stats(stats);
 
-	gr_printf_no_resize(gr_screen.center_offset_x + 20, gr_screen.center_offset_y + 160,
-	                    "Uniform buffer size: " SIZE_T_ARG, UniformBufferManager->getBufferSize());
-	gr_printf_no_resize(gr_screen.center_offset_x + 20, gr_screen.center_offset_y + 160 + line_height,
-	                    "Currently used data: " SIZE_T_ARG, UniformBufferManager->getCurrentlyUsedSize());
+	return stats;
 }
 
+static bool Imgui_frame_active = false;
+
 void gr_imgui_begin_frame()
 {
+	if (Imgui_frame_active) {
+		return;
+	}
+
+	// The stub renderer (standalone server) never assigns the ImGui entry points.
+	if (!gr_screen.gf_imgui_new_frame || !ImGui::GetCurrentContext()) {
+		return;
+	}
+
 	gr_imgui_new_frame();      // renderer backend (OpenGL/Vulkan)
 	ImGui_ImplSDL3_NewFrame(); // platform backend, derives the display size from the SDL window
 
@@ -3205,6 +3221,23 @@ void gr_imgui_begin_frame()
 	}
 
 	ImGui::NewFrame();
+	Imgui_frame_active = true;
+}
+
+void gr_imgui_end_frame()
+{
+	if (!Imgui_frame_active) {
+		return;
+	}
+
+	ImGui::Render();
+	gr_imgui_render_draw_data();
+	Imgui_frame_active = false;
+}
+
+bool gr_imgui_frame_active()
+{
+	return Imgui_frame_active;
 }
 
 void gr_flip(bool execute_scripting)
@@ -3225,9 +3258,13 @@ void gr_flip(bool execute_scripting)
 
 	model_process_cached_ui_render_instances();
 
-	if (Cmdline_graphics_debug_output) {
-		output_uniform_debug_data();
-	}
+	// Every presented frame drains the frame profiler and contributes the overlay window to
+	// this frame's ImGui pass. Doing it here rather than per game state is what keeps the
+	// profiler's event buffer bounded: collection is global, so the drain has to be too.
+	tracing::profiler_overlay_frame();
+
+	// Closes whatever ImGui frame the overlay (or the lab, or the options screen) opened.
+	gr_imgui_end_frame();
 
 	// IMPORTANT: No rendering may happen after this point until gf_flip()/gr_setup_frame().
 	// gr_reset_immediate_buffer() resets the write offset to 0, so any subsequent immediate
@@ -3496,6 +3533,30 @@ void gr_heap_deallocate(GpuHeap heap_type, size_t data_offset)
 	gpuHeap->freeGpuData(data_offset);
 }
 
+gr_memory_stats gr_get_memory_stats()
+{
+	gr_memory_stats stats;
+
+	// gpu_heaps[] entries stay null when gpu_heap_init() early-returned (GraphicsAPI::Stub, e.g.
+	// a build with both graphics backends disabled), so this must not assume a live heap.
+	auto vertex_heap = get_gpu_heap(GpuHeap::ModelVertex);
+	auto index_heap = get_gpu_heap(GpuHeap::ModelIndex);
+	if (vertex_heap != nullptr && index_heap != nullptr) {
+		stats.model_heap_valid = true;
+		stats.model_vertex_heap_used = vertex_heap->usedBytes();
+		stats.model_vertex_heap_size = vertex_heap->bufferSize();
+		stats.model_index_heap_used = index_heap->usedBytes();
+		stats.model_index_heap_size = index_heap->bufferSize();
+	}
+
+	stats.locked_bitmap_ram_valid = true;
+	stats.locked_bitmap_ram_bytes = bm_texture_ram;
+
+	gr_screen.gf_get_memory_stats(stats);
+
+	return stats;
+}
+
 void gr_set_gamma(float gamma)
 {
 	if (gr_screen.mode == GraphicsAPI::Stub) {

code/graphics/2d.h

@@ -690,6 +690,56 @@ enum class BufferUsageHint { Static, Dynamic, Streaming, PersistentMapping };
  */
 typedef void* gr_sync;
 
+/**
+ * @brief Per-backend diagnostic counters, populated only when -gr_debug is active
+ *
+ * Each stat group carries its own "valid" flag since not every backend collects every
+ * group (e.g. per-draw-call counters currently only exist in the Vulkan backend). See
+ * gr_get_debug_stats().
+ */
+struct gr_debug_stats {
+	bool uniform_buffer_valid = false;
+	size_t uniform_buffer_size = 0;
+	size_t uniform_buffer_used = 0;
+
+	bool draw_stats_valid = false;
+	int draw_calls = 0;
+	int draw_indexed_calls = 0;
+	int total_vertices = 0;
+	int total_indices = 0;
+	int apply_material_calls = 0;
+	int apply_material_failures = 0;
+	int no_pipeline_skips = 0;
+	int descriptor_sets_allocated = 0;
+	int descriptor_writes = 0;
+	size_t pipeline_count = 0;
+	int on_demand_texture_uploads = 0;
+};
+
+/**
+ * @brief Cross-backend memory usage snapshot for the profiler overlay's memory panel
+ *
+ * Unlike gr_debug_stats, this is always populated when queried (no -gr_debug gate) -- memory
+ * usage is meant to be visible to anyone with the profiler overlay open. Each group still carries
+ * its own "valid" flag since not every backend/build collects every group (e.g. both graphics
+ * backends disabled at build time). See gr_get_memory_stats().
+ */
+struct gr_memory_stats {
+	bool model_heap_valid = false;
+	size_t model_vertex_heap_used = 0;
+	size_t model_vertex_heap_size = 0;
+	size_t model_index_heap_used = 0;
+	size_t model_index_heap_size = 0;
+
+	bool locked_bitmap_ram_valid = false;
+	size_t locked_bitmap_ram_bytes = 0;
+
+	bool gpu_purpose_valid = false;
+	size_t gpu_texture_bytes = 0;
+	size_t gpu_geometry_bytes = 0;
+	size_t gpu_render_target_bytes = 0;
+};
+
 typedef struct screen {
 	int max_w = 0, max_h = 0; // Width and height
 	int max_w_unscaled = 0, max_h_unscaled = 0;
@@ -963,6 +1013,14 @@ typedef struct screen {
 	std::function<void(const char* name)> gf_push_debug_group;
 	std::function<void()> gf_pop_debug_group;
 
+	// Fills in whichever debug_stats groups this backend collects. Defaults to a no-op
+	// so backends without per-draw-call counters (OpenGL, stub) don't have to assign it.
+	std::function<void(gr_debug_stats& stats)> gf_get_debug_stats = [](gr_debug_stats&) {};
+
+	// Fills in whichever memory_stats groups this backend collects (GPU-purpose byte totals).
+	// Defaults to a no-op so backends without per-purpose tagging don't have to assign it.
+	std::function<void(gr_memory_stats& stats)> gf_get_memory_stats = [](gr_memory_stats&) {};
+
 	std::function<int()> gf_create_query_object;
 	std::function<void(int obj, QueryType type)> gf_query_value;
 	std::function<bool(int obj)> gf_query_value_available;
@@ -1153,6 +1211,23 @@ bool gr_is_screenshot_requested();
 //#define gr_flip				GR_CALL(gr_screen.gf_flip)
 void gr_flip(bool execute_scripting = true);
 
+/**
+ * @brief Collects whichever graphics-API debug stats are available for the active backend
+ *
+ * Returns a default-constructed (all-invalid) gr_debug_stats unless -gr_debug is active. Safe
+ * to call every frame regardless of backend or debug flag.
+ */
+gr_debug_stats gr_get_debug_stats();
+
+/**
+ * @brief Collects whichever cross-backend memory usage stats are available
+ *
+ * Unlike gr_get_debug_stats(), this is always populated (no -gr_debug gate) -- memory usage is
+ * meant to be visible whenever the profiler overlay is open. Safe to call every frame regardless
+ * of backend or build configuration; groups a backend/build doesn't support stay invalid/zero.
+ */
+gr_memory_stats gr_get_memory_stats();
+
 inline void gr_setup_frame() {
 	gr_screen.gf_setup_frame();
 }
@@ -1310,6 +1385,16 @@ inline void gr_post_process_restore_zbuffer()
  */
 void gr_imgui_begin_frame();
 
+/**
+ * @brief Renders and submits the open ImGui frame, if any. Called by gr_flip().
+ */
+void gr_imgui_end_frame();
+
+/**
+ * @brief Whether an ImGui frame is currently open for contributions
+ */
+bool gr_imgui_frame_active();
+
 inline void gr_render_primitives(material* material_info,
 	primitive_type prim_type,
 	vertex_layout* layout,

code/graphics/opengl/gropengl.cpp

@@ -1164,6 +1164,7 @@ void gr_opengl_init_function_pointers()
 
 	gr_screen.gf_is_capable = gr_opengl_is_capable;
 	gr_screen.gf_get_property = gr_opengl_get_property;
+	gr_screen.gf_get_memory_stats = gr_opengl_get_memory_stats;
 
 	gr_screen.gf_push_debug_group = gr_opengl_push_debug_group;
 	gr_screen.gf_pop_debug_group = gr_opengl_pop_debug_group;

code/graphics/opengl/gropengldraw.cpp

@@ -760,6 +760,66 @@ void opengl_scene_texture_shutdown()
 	Scene_framebuffer_in_frame = false;
 }
 
+size_t opengl_get_scene_render_target_bytes()
+{
+	// The bytes for each pixel come from the internal formats that opengl_setup_scene_textures()
+	// gives to these textures: GL_RGBA16F holds 8 bytes, GL_RGBA8 and GL_DEPTH24_STENCIL8 hold 4.
+	// Keep the values below equal to the formats at the creation sites in that function.
+	constexpr size_t RGBA16F_BYTES = 8;
+	constexpr size_t RGBA8_BYTES = 4;
+	constexpr size_t DEPTH24_STENCIL8_BYTES = 4;
+
+	size_t bytes = 0;
+
+	auto add_texture = [&bytes](GLuint texture_id, size_t width, size_t height, size_t bytes_per_pixel,
+							 size_t samples = 1) {
+		if (texture_id == 0) {
+			return;
+		}
+		bytes += width * height * bytes_per_pixel * samples;
+	};
+
+	const auto scene_w = static_cast<size_t>(Scene_texture_width);
+	const auto scene_h = static_cast<size_t>(Scene_texture_height);
+
+	add_texture(Scene_color_texture, scene_w, scene_h, RGBA16F_BYTES);
+	add_texture(Scene_ldr_texture, scene_w, scene_h, RGBA8_BYTES);
+	add_texture(Scene_position_texture, scene_w, scene_h, RGBA16F_BYTES);
+	add_texture(Scene_normal_texture, scene_w, scene_h, RGBA16F_BYTES);
+	add_texture(Scene_specular_texture, scene_w, scene_h, RGBA8_BYTES);
+	add_texture(Scene_emissive_texture, scene_w, scene_h, RGBA16F_BYTES);
+	add_texture(Scene_composite_texture, scene_w, scene_h, RGBA16F_BYTES);
+	add_texture(Scene_luminance_texture, scene_w, scene_h, RGBA16F_BYTES);
+	add_texture(Cockpit_depth_texture, scene_w, scene_h, DEPTH24_STENCIL8_BYTES);
+	add_texture(Scene_depth_texture, scene_w, scene_h, DEPTH24_STENCIL8_BYTES);
+
+	// The multisample textures hold one value for each sample, thus their bytes go up with the
+	// MSAA level. Cmdline_msaa_enabled holds the number of samples and is 0 when MSAA is off.
+	const auto samples = static_cast<size_t>(std::max(1, Cmdline_msaa_enabled));
+
+	add_texture(Scene_color_texture_ms, scene_w, scene_h, RGBA16F_BYTES, samples);
+	add_texture(Scene_position_texture_ms, scene_w, scene_h, RGBA16F_BYTES, samples);
+	add_texture(Scene_normal_texture_ms, scene_w, scene_h, RGBA16F_BYTES, samples);
+	add_texture(Scene_specular_texture_ms, scene_w, scene_h, RGBA8_BYTES, samples);
+	add_texture(Scene_emissive_texture_ms, scene_w, scene_h, RGBA16F_BYTES, samples);
+	add_texture(Scene_depth_texture_ms, scene_w, scene_h, DEPTH24_STENCIL8_BYTES, samples);
+
+	// The back buffer and gamma blit textures use the size of the screen, not the (clamped) size
+	// of the scene textures.
+	const auto screen_w = static_cast<size_t>(gr_screen.max_w);
+	const auto screen_h = static_cast<size_t>(gr_screen.max_h);
+
+	add_texture(Back_texture, screen_w, screen_h, RGBA16F_BYTES);
+	add_texture(Back_depth_texture, screen_w, screen_h, DEPTH24_STENCIL8_BYTES);
+	add_texture(GammaBlit_texture, screen_w, screen_h, RGBA8_BYTES);
+
+	// The two distortion textures always have the size 32x32.
+	add_texture(Distortion_texture[0], 32, 32, RGBA8_BYTES);
+	add_texture(Distortion_texture[1], 32, 32, RGBA8_BYTES);
+
+	return bytes;
+}
+
 void gr_opengl_scene_texture_begin()
 {
 	if ( !Scene_texture_initialized ) {

code/graphics/opengl/gropengldraw.h

@@ -57,6 +57,15 @@ void gr_opengl_render_shield_impact(shield_material* material_info,
 
 void opengl_setup_scene_textures();
 void opengl_scene_texture_shutdown();
+
+/**
+ * @brief Gives the bytes that the scene, backbuffer, and distortion textures hold
+ *
+ * The profiler overlay's memory panel adds this value to the "render targets" group. The function
+ * counts only the textures that exist at the moment of the call, thus it gives 0 before
+ * opengl_setup_scene_textures() runs and after opengl_scene_texture_shutdown() runs.
+ */
+size_t opengl_get_scene_render_target_bytes();
 void gr_opengl_scene_texture_begin();
 void gr_opengl_scene_texture_end();
 void gr_opengl_copy_effect_texture();