Add support for multiple in-flight frames

src/main.c

@@ -29,6 +29,7 @@ typedef struct SwapChainSupportDetails {
     VkPresentModeKHR* present_modes;
 } SwapChainSupportDetails;
 
+#define MAX_FRAMES_IN_FLIGHT 2
 
 typedef struct ApplicationState {
     GLFWwindow* window;
@@ -64,13 +65,13 @@ typedef struct ApplicationState {
     VkFramebuffer* framebuffers;
 
     VkCommandPool commandPool;
-    VkCommandBuffer command_buffer;
+    VkCommandBuffer command_buffer[MAX_FRAMES_IN_FLIGHT];
 
     //synchronization objects
     //semaphoers are gpu<->gpu, fences are cpu<->gpu
-    VkSemaphore image_available_semaph;
-    VkSemaphore render_finished_sempah;
-    VkFence in_flight_frames;
+    VkSemaphore image_available_semaph[MAX_FRAMES_IN_FLIGHT];
+    VkSemaphore render_finished_sempah[MAX_FRAMES_IN_FLIGHT];
+    VkFence in_flight_frames[MAX_FRAMES_IN_FLIGHT];
 } ApplicationState;
 
 typedef struct QueueFamilyIndices {
@@ -627,6 +628,7 @@ void create_render_pass(ApplicationState* state) {
     //wait on the color attachment
     dependency.srcStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT;
     dependency.srcAccessMask = 0;
+    //the part of the subpass when the attachment is written has to wait
     dependency.dstStageMask = VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT;
     dependency.dstAccessMask = VK_ACCESS_COLOR_ATTACHMENT_WRITE_BIT;
 
@@ -871,9 +873,9 @@ void create_command_buffer(ApplicationState* state) {
     //VK_COMMAND_BUFFER_LEVEL_PRIMARY: Can be submitted to a queue for execution, but cannot be called from other command buffers.
     //VK_COMMAND_BUFFER_LEVEL_SECONDARY: Cannot be submitted directly, but can be called from primary command buffers
     command_buf_allocate_info.level = VK_COMMAND_BUFFER_LEVEL_PRIMARY;
-    command_buf_allocate_info.commandBufferCount = 1;
+    command_buf_allocate_info.commandBufferCount = MAX_FRAMES_IN_FLIGHT;
 
-    if (vkAllocateCommandBuffers(state->device, &command_buf_allocate_info, &state->command_buffer) != VK_SUCCESS) {
+    if (vkAllocateCommandBuffers(state->device, &command_buf_allocate_info, state->command_buffer) != VK_SUCCESS) {
         printf("failed to allocated command buffer");
         exit(1);
     }
@@ -951,11 +953,13 @@ void create_sync_objects(ApplicationState* state) {
     //initialize it to signalled so we can draw the first frame
     fence_info.flags = VK_FENCE_CREATE_SIGNALED_BIT;
 
-    if (vkCreateSemaphore(state->device, &semaphore_info, NULL, &state->image_available_semaph) != VK_SUCCESS ||
-            vkCreateSemaphore(state->device, &semaphore_info, NULL, &state->render_finished_sempah) != VK_SUCCESS ||
-            vkCreateFence(state->device, &fence_info, NULL, &state->in_flight_frames)) {
-        printf("failed to create sync objects\n");
-        exit(1);
+    for (int i = 0; i < MAX_FRAMES_IN_FLIGHT; i++) {
+        if (vkCreateSemaphore(state->device, &semaphore_info, NULL, &state->image_available_semaph[i]) != VK_SUCCESS ||
+                vkCreateSemaphore(state->device, &semaphore_info, NULL, &state->render_finished_sempah[i]) != VK_SUCCESS ||
+                vkCreateFence(state->device, &fence_info, NULL, &state->in_flight_frames[i])) {
+            printf("failed to create sync objects\n");
+            exit(1);
+        }
     }
 }
 
@@ -974,37 +978,36 @@ void init_vulkan(ApplicationState* state) {
     create_sync_objects(state);
 }
 
-void draw_frame(ApplicationState* state) {
+void draw_frame(ApplicationState* state, uint32_t current_frame) {
     //wait for the previous frame to be rendered
-    vkWaitForFences(state->device, 1, &state->in_flight_frames, VK_TRUE, UINT64_MAX);
-    vkResetFences(state->device, 1, &state->in_flight_frames);
+    vkWaitForFences(state->device, 1, &state->in_flight_frames[current_frame], VK_TRUE, UINT64_MAX);
+    vkResetFences(state->device, 1, &state->in_flight_frames[current_frame]);
 
     uint32_t image_index;
     //get images from the swapchain and signal when the image is ready
-    vkAcquireNextImageKHR(state->device, state->swapchain, UINT64_MAX, state->image_available_semaph, VK_NULL_HANDLE, &image_index);
+    vkAcquireNextImageKHR(state->device, state->swapchain, UINT64_MAX, state->image_available_semaph[current_frame], VK_NULL_HANDLE, &image_index);
 
     //reset and setup the commands we want to run
-    vkResetCommandBuffer(state->command_buffer, 0);
-    record_command_buffer(state, state->command_buffer, image_index);
-
+    vkResetCommandBuffer(state->command_buffer[current_frame], 0);
+    record_command_buffer(state, state->command_buffer[current_frame], image_index);
 
     //specify what to wait for before execution can begin
     VkSubmitInfo submit_info = {0};
     submit_info.sType = VK_STRUCTURE_TYPE_SUBMIT_INFO;
 
-    VkSemaphore to_wait[] = {state->image_available_semaph};
+    VkSemaphore to_wait[] = {state->image_available_semaph[current_frame]};
     VkPipelineStageFlags wait_stages[] = {VK_PIPELINE_STAGE_COLOR_ATTACHMENT_OUTPUT_BIT};
     submit_info.waitSemaphoreCount = 1;
     submit_info.pWaitSemaphores = to_wait;
     submit_info.pWaitDstStageMask = wait_stages;
     submit_info.commandBufferCount = 1;
-    submit_info.pCommandBuffers = &state->command_buffer;
+    submit_info.pCommandBuffers = &state->command_buffer[current_frame];
 
-    VkSemaphore signal_semaphores[] = {state->render_finished_sempah};
+    VkSemaphore signal_semaphores[] = {state->render_finished_sempah[current_frame]};
     submit_info.signalSemaphoreCount = 1;
     submit_info.pSignalSemaphores = signal_semaphores;
 
-    if (vkQueueSubmit(state->graphics_queue, 1, &submit_info, state->in_flight_frames) != VK_SUCCESS) {
+    if (vkQueueSubmit(state->graphics_queue, 1, &submit_info, state->in_flight_frames[current_frame]) != VK_SUCCESS) {
         printf("failed to submit draw command buffer");
         exit(1);
     }
@@ -1021,19 +1024,24 @@ void draw_frame(ApplicationState* state) {
     present_info.pResults = NULL;
 
     vkQueuePresentKHR(state->present_queue, &present_info);
+
+    current_frame = (current_frame + 1) % MAX_FRAMES_IN_FLIGHT;
 }
 
 void main_loop(ApplicationState* state) {
+    uint32_t current_frame = 0;
     while(!glfwWindowShouldClose(state->window)) {
-        draw_frame(state);
+        draw_frame(state, current_frame);
         glfwPollEvents();
     }
 }
 
 void terminate(ApplicationState* state) {
-    vkDestroyFence(state->device, state->in_flight_frames, NULL);
-    vkDestroySemaphore(state->device, state->image_available_semaph, NULL);
-    vkDestroySemaphore(state->device, state->render_finished_sempah, NULL);
+    for (int i = 0; i < MAX_FRAMES_IN_FLIGHT; i++) {
+        vkDestroyFence(state->device, state->in_flight_frames[i], NULL);
+        vkDestroySemaphore(state->device, state->image_available_semaph[i], NULL);
+        vkDestroySemaphore(state->device, state->render_finished_sempah[i], NULL);
+    }
     vkDestroyCommandPool(state->device, state->commandPool, NULL);
     for (int i = 0; i < state->swapchain_image_count; i++) {
         vkDestroyFramebuffer(state->device, state->framebuffers[i], NULL);