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Vulkan Nitty-Gritty



I am surprised at how quickly Vulkan development is coming together. The API is ridiculously verbose, but at the same time it eliminates a lot of hidden states and implicit behavior that made OpenGL difficult to work with. I have vertex buffers working now. Vertices in the new engine will always use this layout:

    struct VkVertex
        float position[3];
        float normal[3];
        float texcoords0[2];
        float texcoords1[2];
        float tangent[3];
        unsigned char color[4];
        unsigned char boneweights[4];
        unsigned char boneindices[4];

Note there are no longer vertex binormals, as these are calculated in the vertex shader, with the assumption that the texture coordinates have no shearing. There are two sets of UV coordinates available to use. Up to 256 bones per mesh are supported.

I am creating a few internal classes for Vulkan, out of necessity, and the structure of the new renderer is forming. It's very interesting stuff:

	class VkMesh
		Vk* environment;
		VkBuffer vertexBuffer;
		VmaAllocation allocation;
		VkBuffer indexBuffer;
		VmaAllocation indexallocation;


I have hit the memory management part of Vulkan. Something that used to be neatly done for you is now pushed onto the developer for no apparent reason. I think this is really pointless because we're all going to end up using a bunch of open-source helper libraries anyways. It's like they are partially open-sourcing the driver.


You can't just allocate memory buffers as you wish. From vulkan-tutorial.com:


It should be noted that in a real world application, you're not supposed to actually call vkAllocateMemory for every individual buffer. The maximum number of simultaneous memory allocations is limited by the maxMemoryAllocationCount physical device limit, which may be as low as 4096 even on high end hardware like an NVIDIA GTX 1080. The right way to allocate memory for a large number of objects at the same time is to create a custom allocator that splits up a single allocation among many different objects by using the offset parameters that we've seen in many functions.

You can either implement such an allocator yourself, or use the VulkanMemoryAllocator library provided by the GPUOpen initiative. However, for this tutorial it's okay to use a separate allocation for every resource, because we won't come close to hitting any of these limits for now.

Nvidia explains it visually. It is better to allocate a smaller number of memory blocks and buffers and split them up:


I added the Vulkan Memory Allocator library and it works. I honestly have no idea what it is doing, but I am able to delete the Vulkan instance with no errors so that's good.

Shared contexts are also working so we can have multiple Windows, just like in the OpenGL renderer:

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The good thing about all this is that to create a simple triangle, you might pass us a function that is "CreateTriangle" with some parameters.  And save us a lot of pain...


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That is the biggest goal of an engine, simplifying the end-user's life.  We usually don't have to worry about what's under the hood but it's nice to see details of what Josh is working with.

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  • Blog Entries

    • By Josh in Josh's Dev Blog 2
      Documentation in Leadwerks 5 will start in the header files, where functions descriptions are being added directly like this:
      /// <summary> /// Sets the height of one terrain point. /// </summary> /// <param name="x">Horizontal position of the point to modify.</param> /// <param name="y">Vertical position of the point to modify.</param> /// <param name="height">Height to set, in the range -1.0 to +1.0.</param> virtual void SetHeight(const int x, const int y, const float height); This will make function descriptions appear automatically in Visual Studio, to help you write code faster and more easily:

      Visual Studio can also generate an XML file containing all of the project's function descriptions as part of the build process. The generated XML file will serve as the basis for the online documentation and Visual Studio Code extension for Lua. This is how I see it working:

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      class Entity { private: Vec3 m_position; public: const Vec3& position; }; Entity::Entity() : position(m_position) {} It is even possible to make constructors private so that the programmer has to use the correct CreateTerrain() or whatever command, instead of trying to construct a new instance of the class, with unpredictable results. Interestingly, the constructor itself has to be added as a friend function for this to work.
      class Terrein { private: Terrain(); public: friend shared_ptr<World> CreateTerrain(shared_ptr<World>, int, int, int) }; The only difference is that inside the CreateTerrain function I have to do this:
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    • By Josh in Josh's Dev Blog 8
      An often-requested feature for terrain building commands in Leadwerks 5 is being implemented. Here is my script to create a terrain. This creates a 256 x 256 terrain with one terrain point every meter, and a maximum height of +/- 50 meters:
      --Create terrain local terrain = CreateTerrain(world,256,256) terrain:SetScale(256,100,256) Here is what it looks like:

      A single material layer is then added to the terrain.
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      This gives you an idea of the basic terrain building API in Leadwerks 5, and it will serve as the foundation for more advanced terrain features. This will be included in the next beta.
    • By Josh in Josh's Dev Blog 0
      A new update is available for beta testers.
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      Precompiled headers have been integrated into the example project. The Debug build will compile in about 20 seconds the first run, and compile in just 2-3 seconds thereafter. An example class is included which shows how to add files to your game project for optimum compile times. Even if you edit one of your header files, your game will still compile in just a few seconds in debug mode! Integrating precompiled headers into the engine actually brought the size of the static libraries down significantly, so the download is only about 350 MB now.
      Enums Everywhere
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      Almost all the pre-processor macros have been removed from the Visual Studio project, with just a couple ones left. Overall the headers and project structure have been massively cleaned up.
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