QRhiRenderBuffer Class

Renderbuffer resource. More...

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

Public Types

struct NativeRenderBuffer
enum Flag { UsedWithSwapChainOnly }
flags Flags
enum Type { DepthStencil, Color }

Public Functions

virtual bool create() = 0
virtual bool createFrom(QRhiRenderBuffer::NativeRenderBuffer src)
QRhiRenderBuffer::Flags flags() const
QSize pixelSize() const
int sampleCount() const
void setFlags(QRhiRenderBuffer::Flags f)
void setPixelSize(const QSize &sz)
void setSampleCount(int s)
void setType(QRhiRenderBuffer::Type t)
QRhiRenderBuffer::Type type() const

Reimplemented Public Functions

virtual QRhiResource::Type resourceType() const override

Detailed Description

Renderbuffers cannot be sampled or read but have some benefits over textures in some cases:

A DepthStencil renderbuffer may be lazily allocated and be backed by transient memory with some APIs. On some platforms this may mean the depth/stencil buffer uses no physical backing at all.

Color renderbuffers are useful since QRhi::MultisampleRenderBuffer may be supported even when QRhi::MultisampleTexture is not.

How the renderbuffer is implemented by a backend is not exposed to the applications. In some cases it may be backed by ordinary textures, while in others there may be a different kind of native resource used.

Renderbuffers that are used as (and are only used as) depth-stencil buffers in combination with a QRhiSwapChain's color buffers should have the UsedWithSwapChainOnly flag set. This serves a double purpose: such buffers, depending on the backend and the underlying APIs, be more efficient, and QRhi provides automatic sizing behavior to match the color buffers, which means calling setPixelSize() and create() are not necessary for such renderbuffers.

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

Member Type Documentation

enum QRhiRenderBuffer::Flag
flags QRhiRenderBuffer::Flags

Flag values for flags() and setFlags()

QRhiRenderBuffer::UsedWithSwapChainOnly1 << 0For DepthStencil renderbuffers this indicates that the renderbuffer is only used in combination with a QRhiSwapChain, and never in any other way. This provides automatic sizing and resource rebuilding, so calling setPixelSize() or create() is not needed whenever this flag is set. This flag value may also trigger backend-specific behavior, for example with OpenGL, where a separate windowing system interface API is in use (EGL, GLX, etc.), the flag is especially important as it avoids creating any actual renderbuffer resource as there is already a windowing system provided depth/stencil buffer as requested by QSurfaceFormat.

The Flags type is a typedef for QFlags<Flag>. It stores an OR combination of Flag values.

enum QRhiRenderBuffer::Type

Specifies the type of the renderbuffer

QRhiRenderBuffer::DepthStencil0Combined depth/stencil

Member Function Documentation

[pure virtual] bool QRhiRenderBuffer::create()

Creates the corresponding native graphics resources. If there are already resources present due to an earlier create() with no corresponding destroy(), then destroy() is called implicitly first.

Returns true when successful, false when a graphics operation failed. Regardless of the return value, calling destroy() is always safe.

[virtual] bool QRhiRenderBuffer::createFrom(QRhiRenderBuffer::NativeRenderBuffer src)

Similar to create() except that no new native renderbuffer objects are created. Instead, the native renderbuffer object specified by src is used.

This allows importing an existing renderbuffer object (which must belong to the same device or sharing context, depending on the graphics API) from an external graphics engine.

Note: This is currently applicable to OpenGL only. This function exists solely to allow importing a renderbuffer object that is bound to some special, external object, such as an EGLImageKHR. Once the application performed the glEGLImageTargetRenderbufferStorageOES call, the renderbuffer object can be passed to this function to create a wrapping QRhiRenderBuffer, which in turn can be passed in as a color attachment to a QRhiTextureRenderTarget to enable rendering to the EGLImage.

Note: pixelSize(), sampleCount(), and flags() must still be set correctly. Passing incorrect sizes and other values to QRhi::newRenderBuffer() and then following it with a createFrom() expecting that the native renderbuffer object alone is sufficient to deduce such values is wrong and will lead to problems.

Note: QRhiRenderBuffer does not take ownership of the native object, and destroy() will not release that object.

Note: This function is only implemented when the QRhi::RenderBufferImport feature is reported as supported. Otherwise, the function does nothing and the return value is false.

Returns true when successful, false when not supported.

QRhiRenderBuffer::Flags QRhiRenderBuffer::flags() const

Returns the flags.

See also setFlags().

QSize QRhiRenderBuffer::pixelSize() const

Returns the pixel size.

See also setPixelSize().

[override virtual] QRhiResource::Type QRhiRenderBuffer::resourceType() const

Reimplements: QRhiResource::resourceType() const.

Returns the resource type.

int QRhiRenderBuffer::sampleCount() const

Returns the sample count. 1 means no multisample antialiasing.

See also setSampleCount().

void QRhiRenderBuffer::setFlags(QRhiRenderBuffer::Flags f)

Sets the flags to f.

See also flags().

void QRhiRenderBuffer::setPixelSize(const QSize &sz)

Sets the size (in pixels) to sz.

See also pixelSize().

void QRhiRenderBuffer::setSampleCount(int s)

Sets the sample count to s.

See also sampleCount().

void QRhiRenderBuffer::setType(QRhiRenderBuffer::Type t)

Sets the type to t.

See also type().

QRhiRenderBuffer::Type QRhiRenderBuffer::type() const

Returns the renderbuffer type.

See also setType().

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