Using descriptor indexing and texture arrays in Vulkan

Before we dive deep into the glTF and PBR implementation code, let's look at some lower-level functionality that will be required to minimize the number of Vulkan descriptor sets in applications that use lots of materials with multiple textures. Descriptor indexing is an extremely useful feature recently added to Vulkan 1.2 and, at the time of writing this book, is already supported on some devices. It allows us to create unbounded descriptor sets and use non-uniform dynamic indexing to access textures inside them. This way, materials can be stored in shader storage buffers and each one can reference all the required textures using integer identifiers (IDs). These IDs can be fetched from a shader storage buffer object (SSBO) and are directly used to index into an appropriate descriptor set that contains all the textures required by our application. Vulkan descriptor indexing is rather similar to the OpenGL bindless textures...