Before you can start using any function from Vulkan and vulkano, the first thing to do is to create an instance. Creating an instance tries to load Vulkan from the system and reads the list of available implementations.
Creating an instance takes three optional parameters which aren't going to cover for now. You can
check the documentation of
for more information.
use vulkano::instance::Instance; use vulkano::instance::InstanceExtensions; let instance = Instance::new(None, &InstanceExtensions::none(), None) .expect("failed to create instance");
Like many other functions in vulkano, creating an instance returns a
Result. If Vulkan is not
available on the system, this result will contain an error. For the sake of this example we call
expect on the
Result, which prints a message to stderr and terminates the application if it
contains an error. In a real game or application you should handle that situation in a nicer way,
for example by opening a dialog box with an explanation. This is out of scope of this guide.
Before going further you can try your code by running:
The machine you run your program on may have multiple devices that support Vulkan. Before we can ask a video card to perform some operations, we have to enumerate all the physical devices that support Vulkan and choose which one we are going to use for this operation.
In reality a physical device can be a dedicated graphics card, but also an integrated graphics processor or a software implementation. It can be basically anything that allows running Vulkan operations.
As of the writing of this guide, it is not yet possible to use multiple devices simultaneously in an efficient way (eg. SLI/Crossfire). You can use multiple devices simultaneously in the same program, but there is not much point in doing so because you cannot share anything between them. Consequently the best thing to do in practice is to chose one physical device which is going to run everything:
use vulkano::instance::PhysicalDevice; let physical = PhysicalDevice::enumerate(&instance).next().expect("no device available");
enumerate function returns an iterator to the list of available physical devices.
next on it to return the first device, if any. Note that the first device is not
necessarily the best device. In a real program you probably want to leave the choice to the user.
Keep in mind that the list of physical devices can be empty. This happens if Vulkan is installed on the system, but none of the physical devices of the machine are capable of supporting Vulkan. In a real-world application you are encouraged to handle this situation properly as well.