Multiple Vulkan buffer binding points

vk.cpp

Shader

layout (location = 0) in vec3 inPos;
layout (location = 1) in vec3 inColor;
layout (location = 2) in vec3 inPosB;
layout (location = 3) in vec3 inColorB;

...

Application

// Input state
std::array<VkVertexInputBindingDescription,2> vertexInputBinding = {};
vertexInputBinding[0].binding = 0;
vertexInputBinding[0].stride = sizeof(Vertex);
vertexInputBinding[0].inputRate = VK_VERTEX_INPUT_RATE_VERTEX;
vertexInputBinding[1].binding = 1;
vertexInputBinding[1].stride = sizeof(Vertex);
vertexInputBinding[1].inputRate = VK_VERTEX_INPUT_RATE_VERTEX;

// Inpute attribute bindings describe shader attribute locations and memory layouts
std::array<VkVertexInputAttributeDescription, 4> vertexInputAttributs;
vertexInputAttributs[0].binding = 0;
vertexInputAttributs[0].location = 0;
vertexInputAttributs[0].format = VK_FORMAT_R32G32B32_SFLOAT;
vertexInputAttributs[0].offset = offsetof(Vertex, position);
vertexInputAttributs[1].binding = 0;
vertexInputAttributs[1].location = 1;
vertexInputAttributs[1].format = VK_FORMAT_R32G32B32_SFLOAT;
vertexInputAttributs[1].offset = offsetof(Vertex, color);

vertexInputAttributs[2].binding = 1;
vertexInputAttributs[2].location = 2;
vertexInputAttributs[2].format = VK_FORMAT_R32G32B32_SFLOAT;
vertexInputAttributs[2].offset = offsetof(Vertex, position);
vertexInputAttributs[3].binding = 1;
vertexInputAttributs[3].location = 3;
vertexInputAttributs[3].format = VK_FORMAT_R32G32B32_SFLOAT;
vertexInputAttributs[3].offset = offsetof(Vertex, color);

// Vertex input state used for pipeline creation
VkPipelineVertexInputStateCreateInfo vertexInputState = {};
vertexInputState.sType = VK_STRUCTURE_TYPE_PIPELINE_VERTEX_INPUT_STATE_CREATE_INFO;
vertexInputState.vertexBindingDescriptionCount = 2;
vertexInputState.pVertexBindingDescriptions = vertexInputBinding.data();
vertexInputState.vertexAttributeDescriptionCount = 4;
vertexInputState.pVertexAttributeDescriptions = vertexInputAttributs.data();

// Bind
vkCmdBindVertexBuffers(drawCmdBuffers[i], 0, 1, &vertices.buffer, offsets);
vkCmdBindVertexBuffers(drawCmdBuffers[i], 1, 1, &verticesB.buffer, offsets);

why not put both of vertex datas into the same buffer?It seems that they will be handled within the same shader?

I am under the impression that this is an example that teaches us how to properly use vertex input attributes and not an example that is meant to demonstrate optimal usage of buffers. I believe the you are right and using the same buffer would have been a great idea. :)