Rework semaphores & fences

README.md

@@ -0,0 +1,11 @@
+# Vulkan renderer in Zig & SDL2
+
+This is just a project to learn Vulkan using the Zig programming language.
+
+## Dependencies
+
+TODO
+
+## Build
+
+TODO

src/vulkan_renderer.zig

@@ -12,6 +12,8 @@ const SwapchainImage = Utilities.SwapchainImage;
 const enable_validation_layers = builtin.mode == .Debug;
 const validation_layers = [_][*:0]const u8{"VK_LAYER_KHRONOS_validation"};
 
+const MAX_FRAME_DRAWS: u32 = 2;
+
 const apis: []const vk.ApiInfo = &.{
     vk.features.version_1_0,
     vk.features.version_1_1,
@@ -40,6 +42,8 @@ pub const VulkanRenderer = struct {
 
     window: sdl.Window,
 
+    current_frame: u32 = 0,
+
     // Main
     instance: Instance,
     physical_device: vk.PhysicalDevice,
@@ -68,9 +72,9 @@ pub const VulkanRenderer = struct {
     extent: vk.Extent2D,
 
     // Synchronisation
-    image_available: vk.Semaphore,
-    render_finished: vk.Semaphore,
-    frame_fence: vk.Fence,
+    image_available: [MAX_FRAME_DRAWS]vk.Semaphore,
+    render_finished: [MAX_FRAME_DRAWS]vk.Semaphore,
+    draw_fences: [MAX_FRAME_DRAWS]vk.Fence,
 
     debug_utils: ?vk.DebugUtilsMessengerEXT,
 
@@ -78,6 +82,7 @@ pub const VulkanRenderer = struct {
         var self: Self = undefined;
 
         self.window = window;
+        self.current_frame = 0;
         self.allocator = allocator;
         self.vkb = try BaseDispatch.load(try sdl.vulkan.getVkGetInstanceProcAddr());
 
@@ -103,14 +108,17 @@ pub const VulkanRenderer = struct {
     }
 
     pub fn draw(self: *Self) !void {
-        _ = try self.device.waitForFences(1, @ptrCast(&self.frame_fence), vk.TRUE, std.math.maxInt(u64));
-        _ = try self.device.resetFences(1, @ptrCast(&self.frame_fence));
+        // Wait for given fence to signal (open) from last draw before continuing
+        _ = try self.device.waitForFences(1, @ptrCast(&self.draw_fences[self.current_frame]), vk.TRUE, std.math.maxInt(u64));
+        // Manually reset (close) fences
+        try self.device.resetFences(1, @ptrCast(&self.draw_fences[self.current_frame]));
+
         // -- Get next image
         // Get index of next image to be drawn to, and signal semaphore when ready to be drawn to
         const image_index_result = try self.device.acquireNextImageKHR(
             self.swapchain,
             std.math.maxInt(u64),
-            self.image_available,
+            self.image_available[self.current_frame],
             .null_handle,
         );
 
@@ -120,21 +128,22 @@ pub const VulkanRenderer = struct {
 
         const submit_info: vk.SubmitInfo = .{
             .wait_semaphore_count = 1, // Number of semaphores to wait on
-            .p_wait_semaphores = @ptrCast(&self.image_available), // List of semaphores to wait on
+            .p_wait_semaphores = @ptrCast(&self.image_available[self.current_frame]), // List of semaphores to wait on
             .p_wait_dst_stage_mask = &wait_stages, // Stages to check semaphores at
             .command_buffer_count = 1, // Number of command buffers to submit
             .p_command_buffers = @ptrCast(&self.command_buffers[image_index_result.image_index]), // Command buffer to submit
             .signal_semaphore_count = 1, // Number of semaphores to signal
-            .p_signal_semaphores = @ptrCast(&self.render_finished), // List of semaphores to signal when command buffer finishes
+            .p_signal_semaphores = @ptrCast(&self.render_finished[self.current_frame]), // List of semaphores to signal when command buffer finishes
         };
 
         // Submit command buffer to queue
-        try self.device.queueSubmit(self.graphics_queue.handle, 1, @ptrCast(&submit_info), self.frame_fence);
+        try self.device.queueSubmit(self.graphics_queue.handle, 1, @ptrCast(&submit_info), self.draw_fences[self.current_frame]);
+        // try self.device.queueSubmit(self.graphics_queue.handle, 1, @ptrCast(&submit_info), self.frame_fence);
 
         // -- Present rendered image to screen
         const present_info: vk.PresentInfoKHR = .{
             .wait_semaphore_count = 1, // Number of semaphores to wait on
-            .p_wait_semaphores = @ptrCast(&self.render_finished), // Semaphores to wait on
+            .p_wait_semaphores = @ptrCast(&self.render_finished[self.current_frame]), // Semaphores to wait on
             .swapchain_count = 1, // Number of swapchains to present to
             .p_swapchains = @ptrCast(&self.swapchain), // Swapchains to present images to
             .p_image_indices = @ptrCast(&image_index_result.image_index), // Index of images in swapchains to present
@@ -142,6 +151,9 @@ pub const VulkanRenderer = struct {
 
         // Present image
         _ = try self.device.queuePresentKHR(self.presentation_queue.handle, &present_info);
+
+        // Get next frame (use % to keep the current frame below MAX_FRAME_DRAWS)
+        self.current_frame = (self.current_frame + 1) % MAX_FRAME_DRAWS;
     }
 
     pub fn deinit(self: *Self) void {
@@ -149,10 +161,13 @@ pub const VulkanRenderer = struct {
             self.instance.destroyDebugUtilsMessengerEXT(self.debug_utils.?, null);
         }
 
-        _ = self.device.waitForFences(1, @ptrCast(&self.frame_fence), vk.TRUE, std.math.maxInt(u64)) catch undefined;
-        self.device.destroyFence(self.frame_fence, null);
-        self.device.destroySemaphore(self.render_finished, null);
-        self.device.destroySemaphore(self.image_available, null);
+        self.device.deviceWaitIdle() catch undefined;
+
+        for (0..MAX_FRAME_DRAWS) |i| {
+            self.device.destroySemaphore(self.render_finished[i], null);
+            self.device.destroySemaphore(self.image_available[i], null);
+            self.device.destroyFence(self.draw_fences[i], null);
+        }
 
         self.allocator.free(self.command_buffers);
         self.device.destroyCommandPool(self.graphics_command_pool, null);
@@ -638,12 +653,15 @@ pub const VulkanRenderer = struct {
     }
 
     fn createSynchronisation(self: *Self) !void {
-        // Semaphore creation information
-        self.image_available = try self.device.createSemaphore(&.{}, null);
-        self.render_finished = try self.device.createSemaphore(&.{}, null);
-
+        // Fence create information
         const fence_create_info: vk.FenceCreateInfo = .{ .flags = .{ .signaled_bit = true } };
-        self.frame_fence = try self.device.createFence(&fence_create_info, null);
+
+        // Semaphore creation information
+        for (0..MAX_FRAME_DRAWS) |i| {
+            self.image_available[i] = try self.device.createSemaphore(&.{}, null);
+            self.render_finished[i] = try self.device.createSemaphore(&.{}, null);
+            self.draw_fences[i] = try self.device.createFence(&fence_create_info, null);
+        }
     }
 
     fn recordCommands(self: *Self) !void {