From 1350d6adf7c7925834cecd34cc30388dc928141e Mon Sep 17 00:00:00 2001
From: Rebekah Rowe <rebekahrowe9999@gmail.com>
Date: Mon, 15 Jul 2024 06:59:47 -0400
Subject: [PATCH] Implimented a Vertex Staging buffer to make startup and
 buffer-copies faster.

---
 src/main.cpp | 35 ++++++++++++++++++++++++++++++++---
 1 file changed, 32 insertions(+), 3 deletions(-)

diff --git a/src/main.cpp b/src/main.cpp
index 02fb44e..8067e78 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -111,6 +111,8 @@ class VulkanExampleApplication {
 
     std::unique_ptr<vk::raii::DeviceMemory> vk_buffer_vertex_memory; // in order to get a clean desctruction sequence, instantiate the DeviceMemory for the vertex buffer first
     std::unique_ptr<vk::raii::Buffer> vk_buffer_vertex; // https://github.com/KhronosGroup/Vulkan-Hpp/blob/6f72ceca515d59f40d64b64cf2734f6261e1f9f2/RAII_Samples/13_InitVertexBuffer/13_InitVertexBuffer.cpp
+    std::unique_ptr<vk::raii::DeviceMemory> vk_buffer_vertex_staging_memory; // optional, but speeds things up!
+    std::unique_ptr<vk::raii::Buffer> vk_buffer_vertex_staging;
 
     struct Vertex {
         glm::vec2 pos;
@@ -645,11 +647,14 @@ public:
             }
             {
                 const auto vertex_buffer_size = sizeof(triangle_vertices[0]) * triangle_vertices.size();
-                std::tie(this->vk_buffer_vertex, this->vk_buffer_vertex_memory) = CreateBuffer(vertex_buffer_size, vk::BufferUsageFlagBits::eVertexBuffer, vk::MemoryPropertyFlagBits::eHostVisible | vk::MemoryPropertyFlagBits::eHostCoherent);
+                std::tie(this->vk_buffer_vertex_staging, this->vk_buffer_vertex_staging_memory) = CreateBuffer(vertex_buffer_size, vk::BufferUsageFlagBits::eTransferSrc, vk::MemoryPropertyFlagBits::eHostVisible | vk::MemoryPropertyFlagBits::eHostCoherent);
 
-                std::uint8_t* const vertex_buffer_data = static_cast<std::uint8_t*>(this->vk_buffer_vertex_memory->mapMemory(0, vertex_buffer_size));
+                std::uint8_t* const vertex_buffer_data = static_cast<std::uint8_t*>(this->vk_buffer_vertex_staging_memory->mapMemory(0, vertex_buffer_size));
                 memcpy(vertex_buffer_data, triangle_vertices.data(), vertex_buffer_size);
-                this->vk_buffer_vertex_memory->unmapMemory();
+                this->vk_buffer_vertex_staging_memory->unmapMemory();
+
+                std::tie(this->vk_buffer_vertex, this->vk_buffer_vertex_memory) = CreateBuffer(vertex_buffer_size, vk::BufferUsageFlagBits::eTransferDst | vk::BufferUsageFlagBits::eVertexBuffer, vk::MemoryPropertyFlagBits::eDeviceLocal);
+                this->CopyBuffer(*this->vk_buffer_vertex_staging, *this->vk_buffer_vertex, vertex_buffer_size);
             }
             { // syncronizing vars
                 this->vk_semephore_image_available = std::make_unique<vk::raii::Semaphore>(*this->vk_gpu, vk::SemaphoreCreateInfo {});
@@ -704,6 +709,30 @@ protected:
         allocated_buffer->bindMemory(**allocated_buffer_memory, 0);
         return { std::make_unique<vk::raii::Buffer>(std::move(*allocated_buffer)), std::make_unique<vk::raii::DeviceMemory>(std::move(*allocated_buffer_memory)) };
     };
+    void CopyBuffer(const vk::Buffer& src_buffer, const vk::Buffer& dest_buffer, const vk::DeviceSize& size) const {
+        const vk::CommandBufferAllocateInfo command_buffer_allocate_info {
+            .commandPool = **this->vk_command_pool,
+            .level = vk::CommandBufferLevel::ePrimary,
+            .commandBufferCount = 1
+        };
+        const auto command_buffer = std::move(vk::raii::CommandBuffers(*this->vk_gpu, command_buffer_allocate_info).front());
+        command_buffer.begin(vk::CommandBufferBeginInfo { .flags = vk::CommandBufferUsageFlagBits::eOneTimeSubmit });
+
+        const vk::BufferCopy copy_region {
+            //.srcOffset = 0, // Optional
+            //.dstOffset = 0, // Optional
+            .size = size
+        };
+        command_buffer.copyBuffer(src_buffer, dest_buffer, { copy_region });
+        command_buffer.end();
+
+        const vk::SubmitInfo submit_queue {
+            .commandBufferCount = 1,
+            .pCommandBuffers = &*command_buffer,
+        };
+        this->vk_queue_graphics->submit(submit_queue);
+        this->vk_queue_graphics->waitIdle();
+    };
 
 public:
     void Run() {