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Update getting_started.md
Include reference to add_required_extension_features and per-version feature enables. Fix type with CustomQueueDescription.
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@ -141,7 +141,7 @@ auto physical_device_selector_return = phys_device_selector
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if (!physical_device_selector_return) {
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// Handle error
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}
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auto phys_device = phys_device_ret.value ();
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auto phys_device = physical_device_selector_return.value ();
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```
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To select a physical device, call `select()` on the `vkb::PhysicalDeviceSelector` object.
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@ -151,9 +151,11 @@ No cleanup is required for `vkb::PhysicalDevice`.
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The `vkb::PhysicalDeviceSelector` will look for the first device in the list that satisfied all the specified criteria, and if none is found, will return the first device that partially satisfies the criteria.
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The various "require" and "desire" pairs of functions indicate to `vk-bootstrap` what features and capabilities are necessary for an application and what are simply preferred. A "require" function will fail any `VkPhysicalDevice` that doesn't satisfy the constraint, while any criteria that doesn't satisfy the "desire" functions will make the `VkPhysicalDevice` only 'partially satisfy'.
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The various "require" functions indicate to `vk-bootstrap` what features and capabilities are necessary for an application. A "require" function will fail any `VkPhysicalDevice` that doesn't satisfy the constraint.
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```c
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For example, "requiring" certain device extensions to be supported is done as follows:
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```cpp
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// Application cannot function without this extension
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phys_device_selector.add_required_extension("VK_KHR_timeline_semaphore");
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@ -161,10 +163,51 @@ phys_device_selector.add_required_extension("VK_KHR_timeline_semaphore");
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phys_device_selector.add_desired_extension("VK_KHR_imageless_framebuffer");
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```
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While requiring that certain features are available is as follows:
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```cpp
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VkPhysicalDeviceFeatures required_features{};
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required_features.multiViewport = true;
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phys_device_selector.set_required_features(required_features);
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```
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To enable features for newer versions of Vulkan, use `set_required_features_11()`, `set_required_features_12()`, and `set_required_features_13()` and follow the same pattern as `set_required_features()` of passing in the features struct, corresponding to the version.
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Note that `set_required_features_11()` was released with 1.2, so it cannot be used for 1.1 only capable Vulkan devices.
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Features only available through extensions need to use `add_required_extension_features()`. For example:
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```cpp
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VkPhysicalDeviceDescriptorIndexingFeatures descriptor_indexing_features{};
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descriptor_indexing_features.<features_used> = true;
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phys_device_selector.add_required_extension_features(&descriptor_indexing_features);
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```
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The features and extensions used as selection criteria in `vkb::PhysicalDeviceSelector` automatically propagate into `vkb::DeviceBuilder`. That means the application only needs to state the feature requirement once, and `vk-bootstrap` will handle enabling it on the resulting device.
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Note:
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Because `vk-bootstrap` does not manage creating a `VkSurfaceKHR` handle, it is explicitly passed into the `vkb::PhysicalDeviceSelector` for proper querying of surface support details. Unless the `vkb::InstanceBuilder::set_headless()` function was called, the physical device selector will emit `no_surface_provided` error. If an application does intend to present but cannot create a `VkSurfaceKHR` handle before physical device selection, use `defer_surface_initialization()` to disable the `no_surface_provided` error.
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## Physical Device
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The `vkb::PhysicalDevice` represents a chosen physical device, along with all the necessary details about how to create a `VkDevice` from it with the requested features and extensions. While most use cases will simply give the `vkb::PhysicalDevice` to `vkb::DeviceBuilder`, there are a handful of useful things that can be done with it.
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Adding optional extensions. It is occasionally useful to enable features if they are present but not require that they be available on the physical device.
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This is done using `enable_extension_if_present()` as follows.
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```cpp
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bool supported = phys_device.enable_extension_if_present("VK_KHR_timeline_semaphore");
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if (supported){
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// allows easy feedback whether an extension is supported or not.
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}
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```
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Use `enable_extensions_if_present()` to check if a group of extensions are available, and enable all of them if they are all present. This will *not* enable any extension unless they are all present, useful for handling dependencies between extensions, where one extension requires another one to be enabled.
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## Device Creation
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Once a `VkPhysicalDevice` has been selected, a `VkDevice` can be created. Facilitating that is the `vkb::DeviceBuilder`. Creation and usage follows the forms laid out by `vkb::InstanceBuilder`.
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@ -178,17 +221,6 @@ if (!dev_ret) {
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vkb::Device vkb_device = dev_ret.value();
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```
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The features and extensions used as selection criteria in `vkb::PhysicalDeviceSelector` automatically propagate into `vkb::DeviceBuilder`. Because of this, there is no way to enable features or extensions that were not specified during `vkb::PhysicalDeviceSelector`. This is by design as any feature or extension enabled in a device *must* have support from the `VkPhysicalDevice` it is created with.
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The common method to extend Vulkan functionality in existing API calls is to use the pNext chain. This is accounted for `VkDevice` creation with the `add_pNext` member function of `vkb::DeviceBuilder`. Note: Any structures added to the pNext chain must remain valid until `build()` is called.
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```cpp
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VkPhysicalDeviceDescriptorIndexingFeatures descriptor_indexing_features{};
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auto dev_ret = device_builder.add_pNext(&descriptor_indexing_features)
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.build ();
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```
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To destroy a `vkb::Device`, call `vkb::destroy_device()`.
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```cpp
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vkb::destroy_device(vkb_device);
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@ -222,7 +254,6 @@ for (uint32_t i = 0; i < static_cast<uint32_t>(queue_families.size ()); i++) {
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if (queue_families[i].queueFlags & VK_QUEUE_GRAPHICS_BIT) {
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// Find the first queue family with graphics operations supported
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queue_descriptions.push_back (vkb::CustomQueueDescription (
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i, queue_families[i].queueCount,
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std::vector<float> (queue_families[i].queueCount, 1.0f)));
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}
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}
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