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Vulkan Nitty-Gritty

Josh

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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
	{
	public:
		Vk* environment;
		VkBuffer vertexBuffer;
		VmaAllocation allocation;
		VkBuffer indexBuffer;
		VmaAllocation indexallocation;

		VkMesh();
		~VkMesh();
	};

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.

giphy.gif.9f502d385d20a66c25c40f4204d5c9ef.gif

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

Quote

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:

vulkan_memory_strategy.png.be553b8754ab05b2fd1478f4fdcafcfe.png

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:
Image1.thumb.jpg.a139e97295f7c7fa029d4ec153c183d8.jpg

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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:

      I am also moving all things private to private members. I found a cool trick that allows me to create read-only members. In the example below, you can access the "position" member to get an entity's local position, but you cannot modify it without using the SetPosition() method. This is important because modifying values often involves updating lots of things in the engine under the hood and syncing data with other threads. This also means that any method Visual Studio displays as you are typing is okay to use, and there won't be any undocumented / use-at-your-own risk types of commands like we had in Leadwerks 4.
      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:
      auto terrain = shared_ptr<Terrain>(new Terrain); instead of this, because make_shared() doesn't have access to the Terrain constructor. (If it did, you would be able to create a shared pointer to a new terrain, so we don't want that!)
      auto terrain = make_shared<Terrain>(); I have big expectations for Leadwerks 5, so it makes sense to pay a lot of attention to the coding experience you will have while using this. I hope you like it!
    • 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.
      --Add a material layer local mtl = LoadMaterial("Materials/Dirt/dirt01.mat") local layerID = terrain:AddLayer(mtl) We don't have to do anything else to make the material appear because by default the entire terrain is set to use the first layer, if a material is available there:

      Next we will raise a few terrain points.
      --Modify terrain height for x=-5,5 do for y=-5,5 do h = (1 - (math.sqrt(x*x + y*y)) / 5) * 20 terrain:SetElevation(127 + x, 127 + y, h) end end And then we will update the normals for that whole section, all at once. Notice that we specify a larger grid for the normals update, because the terrain points next to the ones we modified will have their normals affected by the change in height of the neighboring pixel.
      --Update normals of modified and neighboring points terrain:UpdateNormals(127 - 6, 127 - 6, 13, 13) Now we have a small hill.

      Next let's add another layer and apply it to terrain points that are on the side of the hill we just created:
      --Add another layer mtl = LoadMaterial("Materials/Rough-rockface1.json") rockLayerID = terrain:AddLayer(mtl) --Apply layer to sides of hill for x=-5,5 do for y=-5,5 do slope = terrain:GetSlope(127 + x, 127 + y) alpha = math.min(slope / 15, 1.0) terrain:SetMaterial(rockLayerID, 127 + x, 127 + y, alpha) end end We could improve the appearance by giving it a more gradual change in the rock layer alpha, but it's okay for now.

      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.
      Terrain
      The terrain building API is now available and you can begin working with it, This allows you to construct and modify terrains in pure code. Terrain supports up to 256 materials, each with its own albedo, normal, and displacement maps. Collision and raycasting are currently not supported.
      Fast C++ Builds
      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
      Integer arguments have been replaced with enum values for window styles, entity bounds, and load flags. This is nice because the C++ compiler has some error checking so you don't do something like this:
      LoadTexture("grass.dds", WINDOW_FULLSCREEN); Operators have been added to allow combining enum values as bitwise flags.
      A new LOAD_DUMP_INFO LoadFlags value has been added which will print out information about loaded files (I need this to debug the GLTF loader!).
      Early Spring Cleaning
      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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