- Qt 6.6
- Qt GUI
- C++ Classes
- QRhiRenderPassDescriptor
- Qt 6.6.0 Reference Documentation

# QRhiRenderPassDescriptor Class

Render pass resource. More...

Header: | #include <QRhiRenderPassDescriptor>
CMake: | find_package(Qt6 REQUIRED COMPONENTS Gui) target_link_libraries(mytarget PRIVATE Qt6::Gui)
qmake: | QT += gui
Since: | Qt 6.6
Inherits: | QRhiResource

- List of all members, including inherited members

## Public Functions

virtual bool | isCompatible(const QRhiRenderPassDescriptor *other) const = 0
virtual const QRhiNativeHandles * | nativeHandles()
virtual QRhiRenderPassDescriptor * | newCompatibleRenderPassDescriptor() const = 0
virtual QVector<quint32> | serializedFormat() const = 0

## Reimplemented Public Functions

virtual QRhiResource::Type | resourceType() const override

## Detailed Description

A render pass, if such a concept exists in the underlying graphics API, is a collection of attachments (color, depth, stencil) and describes how those attachments are used.

Note: This is a RHI API with limited compatibility guarantees, see QRhi for details.

## Member Function Documentation

### `[pure virtual]` bool QRhiRenderPassDescriptor::isCompatible(const QRhiRenderPassDescriptor *other) const

Returns true if the other QRhiRenderPassDescriptor is compatible with this one, meaning `this` and other can be used interchangebly in QRhiGraphicsPipeline::setRenderPassDescriptor().

The concept of the compatibility of renderpass descriptors is similar to the layout compatibility of QRhiShaderResourceBindings instances. They allow better reuse of QRhiGraphicsPipeline instances: for example, a QRhiGraphicsPipeline instance cache is expected to use these functions to look for a matching pipeline, instead of just comparing pointers, thus allowing a different QRhiRenderPassDescriptor and QRhiShaderResourceBindings to be used in combination with the pipeline, as long as they are compatible.

The exact details of compatibility depend on the underlying graphics API. Two renderpass descriptors created from the same QRhiTextureRenderTarget are always compatible.

Similarly to QRhiShaderResourceBindings, compatibility can also be tested without having two existing objects available. Extracting the opaque blob by calling serializedFormat() allows testing for compatibility by comparing the returned vector to another QRhiRenderPassDescriptor's serializedFormat(). This has benefits in certain situations, because it allows testing the compatibility of a QRhiRenderPassDescriptor with a QRhiGraphicsPipeline even when the QRhiRenderPassDescriptor the pipeline was originally built was is no longer available (but the data returned from its serializedFormat() still is).

See also newCompatibleRenderPassDescriptor() and serializedFormat().

### `[virtual]` const QRhiNativeHandles *QRhiRenderPassDescriptor::nativeHandles()

Returns a pointer to a backend-specific QRhiNativeHandles subclass, such as QRhiVulkanRenderPassNativeHandles. The returned value is `nullptr` when exposing the underlying native resources is not supported by the backend.

See also QRhiVulkanRenderPassNativeHandles.

### `[pure virtual]` QRhiRenderPassDescriptor *QRhiRenderPassDescriptor::newCompatibleRenderPassDescriptor() const

Returns a new QRhiRenderPassDescriptor that is compatible with this one.

This function allows cloning a QRhiRenderPassDescriptor. The returned object is ready to be used, and the ownership is transferred to the caller. Cloning a QRhiRenderPassDescriptor object can become useful in situations where the object is stored in data structures related to graphics pipelines (in order to allow creating new pipelines which in turn requires a renderpass descriptor object), and the lifetime of the renderpass descriptor created from a render target may be shorter than the pipelines. (for example, because the engine manages and destroys renderpasses together with the textures and render targets it was created from) In such a situation, it can be beneficial to store a cloned version in the data structures, and thus transferring ownership as well.

See also isCompatible().

### `[override virtual]` QRhiResource::Type QRhiRenderPassDescriptor::resourceType() const

Reimplements: QRhiResource::resourceType() const.

Returns the resource type.

### `[pure virtual]` QVector<quint32> QRhiRenderPassDescriptor::serializedFormat() const

Returns a vector of integers containing an opaque blob describing the data relevant for compatibility.

Given two QRhiRenderPassDescriptor objects `rp1` and `rp2`, if the data returned from this function is identical, then `rp1->isCompatible(rp2)`, and vice versa hold true as well.

Note: The returned data is meant to be used for storing in memory and comparisons during the lifetime of the QRhi the object belongs to. It is not meant for storing on disk, reusing between processes, or using with multiple QRhi instances with potentially different backends.

See also isCompatible().