Vulkan 学习(16)---- 使用 VertexBuffer
Vertex Buffer
创建一个 VertexBuffer 存储 Vertex data，代替之前在 Shader 中使用固定顶点值的做法
Vertex Shader
修改 GLSL 的 VertexShader 如下:
注意这里指定了 input Vertex data 的 location 和 格式
#version 450
layout(location = 0) in vec2 inPosition;
layout(location = 1) in vec3 inColor;layout(location = 0) out vec3 fragColor;
void main() {gl_Position = vec4(inPosition, 0.0, 1.0);fragColor = inColor;
}
Note:
Shader 中 location 用于表明 VertexData 是如何分布的， 结合输入参数传入的偏移就可以唯一的确定需要的值
Vertex Data
这里指定 Vertex data 如下：
struct Vertex {glm::vec2 pos;glm::vec3 color;
}const std::vector<Vertex> vertices = {{{-0.5f, 0.5f}, {1.0f, 0.0f, 0.0f}},{{-0.5f, -0.5f}, {0.0f, 1.0f, 0.0f}},{{0.5f, 0.5f}, {0.0f, 0.0f, 1.0f}},{{0.5f, -0.5f }, {1.0f, 0.0f, 0.0f} }
};
glm lib 的数据结构可以和 VertexShader 中的 vec2，vec3 结构保持一致,
Vulkan 中的坐标系如下：
VertexInputBindingDescription
VkVertexInputBindingDescription 说明了如何加载 VertexData，包括了步长，绑定索引和加载方式等信息
binding：是一个索引，用于标志顶点缓冲区的绑定位置，如果有多个顶点缓冲区（比如一个存储位置数据，一个存储法线数据，就可以用不同的bindings进行区分stride: 表示每次加载Vertex data的步长inputRate：
VK_VERTEX_INPUT_RATE_VERTEX表示每个顶点都加载一次数据
VK_VERTEX_INPUT_RATE_INSTANCE每个instance加载一次数据
参考实现：
static VkVertexInputBindingDescription getBindingDescription() {VkVertexInputBindingDescription bindingDescription{};// 这里的 binding 默认使用 0， 注意最后要和 vkCmdBindVertexBuffers 参数对应// vkCmdBindVertexBuffers(commandBuffer, 0, 1, vertexBuffers, offsets);bindingDescription.binding = 0;bindingDescription.stride = sizeof(Vertex);bindingDescription.inputRate = VK_VERTEX_INPUT_RATE_VERTEX;return bindingDescription;
}
VertexInputAttributeDescription
VertexInputAttributeDescription 说明了 VertexData 的处理方式，或者说是 VertexData 的顶点属性
typedef struct VkVertexInputAttributeDescription {uint32_t location;uint32_t binding;VkFormat format;uint32_t offset;
} VkVertexInputAttributeDescription;
location: 这里的 location 必须和 Vertex Shader 中的 location 匹配，每个 location 都必须创建一个 VkVertexInputAttributeDescription 结构
binding: 顶点缓冲区的索引，和前面的 InputBindingDescription 对应
format: 可以和 VertexShader 中的数据类型匹配：
//float: VK_FORMAT_R32_SFLOAT
//vec2: VK_FORMAT_R32G32_SFLOAT
//vec3: VK_FORMAT_R32G32B32_SFLOAT
//vec4: VK_FORMAT_R32G32B32A32_SFLOAT
//ivec2: VK_FORMAT_R32G32_SINT
//uvec4: VK_FORMAT_R32G32B32A32_UINT
//double: VK_FORMAT_R64_SFLOAT
offset: 对应的内容在 VertexData 中的偏移
加载 BindingDescription 和 AttributeDescription
在 BindGraphicPipeline 时，在 pVertexInputState 阶段输入 vertexInputInfo
vertexInputInfo 包含了 bindingDescription 和 attributeDescriptions
VkPipelineVertexInputStateCreateInfo vertexInputInfo{};
vertexInputInfo.sType = VK_STRUCTURE_TYPE_PIPELINE_VERTEX_INPUT_STATE_CREATE_INFO;auto bindingDescription = Vertex::getBindingDescription();
auto attributeDescriptions = Vertex::getAttributeDescriptions();vertexInputInfo.vertexBindingDescriptionCount = 1;
vertexInputInfo.vertexAttributeDescriptionCount = static_cast<uint32_t>(attributeDescriptions.size());
vertexInputInfo.pVertexBindingDescriptions = &bindingDescription;
vertexInputInfo.pVertexAttributeDescriptions = attributeDescriptions.data();// create and bind pipeline 的时候会传入这个参数 vertexInputInfo
VkGraphicsPipelineCreateInfo pipelineInfo{};
.....
pipelineInfo.pVertexInputState = &vertexInputInfo;
VertexBuffer 创建 和 绑定
void createVertexBuffer() {VkBufferCreateInfo bufferInfo{};bufferInfo.sType = VK_STRUCTURE_TYPE_BUFFER_CREATE_INFO;bufferInfo.size = sizeof(vertices[0]) * vertices.size();bufferInfo.usage = VK_BUFFER_USAGE_VERTEX_BUFFER_BIT;//VK_SHARING_MODE_EXCLUSIVE 设备队列独享资源，该资源一次只能被一种设备队列族中的队列访问//VK_SHARING_MODE_CONCURRENT 设备队列共享资源，该资源只能一次被多种设备队列族中的队列访问bufferInfo.sharingMode = VK_SHARING_MODE_EXCLUSIVE;if (vkCreateBuffer(device, &bufferInfo, nullptr, &vertexBuffer) != VK_SUCCESS){throw std::runtime_error("failed to create vertex buffer!");}VkMemoryRequirements memRequirements;vkGetBufferMemoryRequirements(device, vertexBuffer, &memRequirements);VkMemoryAllocateInfo allocInfo{};allocInfo.sType = VK_STRUCTURE_TYPE_MEMORY_ALLOCATE_INFO;allocInfo.allocationSize = memRequirements.size;allocInfo.memoryTypeIndex = findMemoryType(memRequirements.memoryTypeBits, VK_MEMORY_PROPERTY_HOST_VISIBLE_BIT | VK_MEMORY_PROPERTY_HOST_COHERENT_BIT);if (vkAllocateMemory(device, &allocInfo, nullptr, &vertexBufferMemory) != VK_SUCCESS) {throw std::runtime_error("failed to allocate vertex buffer memory!");}vkBindBufferMemory(device, vertexBuffer, vertexBufferMemory, 0);void* data;vkMapMemory(device, vertexBufferMemory, 0, bufferInfo.size, 0, &data);memcpy(data, vertices.data(), (size_t)bufferInfo.size);vkUnmapMemory(device, vertexBufferMemory);
}
步骤如下:
- 创建
VertexBuffer对象，注意usage要使用VK_BUFFER_USAGE_VERTEX_BUFFER_BIT - 获取
memRequirements, 关键是memory的大小和类型 allocate对应类型的memoryMapmemory并拷贝对应的顶点数据
最后在 recordCommandBuffer 的时候绑定这个 VertexBuffer 就行
vkCmdBindPipeline(commandBuffer, VK_PIPELINE_BIND_POINT_GRAPHICS, graphicsPipeline);VkBuffer vertexBuffers[] = { vertexBuffer };
VkDeviceSize offsets[] = { 0 };
vkCmdBindVertexBuffers(commandBuffer, 0, 1, vertexBuffers, offsets);
vkCmdDraw(commandBuffer, static_cast<uint32_t>(vertices.size()), 1, 0, 0);