QGLFramebufferObject 类封装 OpenGL 帧缓冲对象。 更多...
| 头： | #include <QGLFramebufferObject> |
| qmake: | QT += opengl |
| Since: | Qt 4.2 |
| 继承： | QPaintDevice |
该类已过时。 提供它是为使旧源代码能继续工作。强烈建议不要在新代码中使用它。
该类在 Qt 4.2 引入。
| enum | Attachment { NoAttachment, CombinedDepthStencil, Depth } |
| QGLFramebufferObject (int width , int height , const QGLFramebufferObjectFormat & format ) | |
| QGLFramebufferObject (const QSize & size , const QGLFramebufferObjectFormat & format ) | |
| QGLFramebufferObject (int width , int height , QGLFramebufferObject::Attachment attachment , GLenum target = GL_TEXTURE_2D, GLenum internal_format = 0) | |
| QGLFramebufferObject (const QSize & size , QGLFramebufferObject::Attachment attachment , GLenum target = GL_TEXTURE_2D, GLenum internal_format = 0) | |
| QGLFramebufferObject (int width , int height , GLenum target = GL_TEXTURE_2D) | |
| QGLFramebufferObject (const QSize & size , GLenum target = GL_TEXTURE_2D) | |
| virtual | ~QGLFramebufferObject () |
| QGLFramebufferObject::Attachment | attachment () const |
| bool | bind () |
| void | drawTexture (const QRectF & target , GLuint textureId , GLenum textureTarget = GL_TEXTURE_2D) |
| void | drawTexture (const QPointF & point , GLuint textureId , GLenum textureTarget = GL_TEXTURE_2D) |
| QGLFramebufferObjectFormat | format () const |
| GLuint | handle () const |
| bool | isBound () const |
| bool | isValid () const |
| bool | release () |
| QSize | size () const |
| GLuint | texture () const |
| QImage | toImage () const |
| virtual QPaintEngine * | paintEngine () const override |
| bool | bindDefault () |
| void | blitFramebuffer (QGLFramebufferObject * target , const QRect & targetRect , QGLFramebufferObject * source , const QRect & sourceRect , GLbitfield buffers = GL_COLOR_BUFFER_BIT, GLenum filter = GL_NEAREST) |
| bool | hasOpenGLFramebufferBlit () |
| bool | hasOpenGLFramebufferObjects () |
| virtual int | metric (QPaintDevice::PaintDeviceMetric metric ) const override |
The QGLFramebufferObject class encapsulates an OpenGL framebuffer object, defined by the
GL_EXT_framebuffer_object
extension. In addition it provides a rendering surface that can be painted on with a
QPainter
, rendered to using native GL calls, or both. This surface can be bound and used as a regular texture in your own GL drawing code. By default, the QGLFramebufferObject class generates a 2D GL texture (using the
GL_TEXTURE_2D
target), which is used as the internal rendering target.
It is important to have a current GL context when creating a QGLFramebufferObject, otherwise initialization will fail.
OpenGL framebuffer objects and pbuffers (see QGLPixelBuffer ) can both be used to render to offscreen surfaces, but there are a number of advantages with using framebuffer objects instead of pbuffers:
render_texture
extension.
当使用 QPainter to paint to a QGLFramebufferObject you should take care that the QGLFramebufferObject is created with the CombinedDepthStencil attachment for QPainter to be able to render correctly. Note that you need to create a QGLFramebufferObject with more than one sample per pixel for primitives to be antialiased when drawing using a QPainter . To create a multisample framebuffer object you should use one of the constructors that take a QGLFramebufferObjectFormat parameter, and set the QGLFramebufferObjectFormat::samples () property to a non-zero value.
When painting to a QGLFramebufferObject using QPainter , the state of the current GL context will be altered by the paint engine to reflect its needs. Applications should not rely upon the GL state being reset to its original conditions, particularly the current shader program, GL viewport, texture units, and drawing modes.
For multisample framebuffer objects a color render buffer is created, otherwise a texture with the specified texture target is created. The color render buffer or texture will have the specified internal format, and will be bound to the
GL_COLOR_ATTACHMENT0
attachment in the framebuffer object.
If you want to use a framebuffer object with multisampling enabled as a texture, you first need to copy from it to a regular framebuffer object using QGLContext::blitFramebuffer().
As of Qt 4.8, it's possible to draw into a QGLFramebufferObject using a QPainter in a separate thread. Note that OpenGL 2.0 or OpenGL ES 2.0 is required for this to work.
注意： This class has been deprecated in favor of QOpenGLFramebufferObject .
This enum type is used to configure the depth and stencil buffers attached to the framebuffer object when it is created.
| 常量 | 值 | 描述 |
|---|---|---|
QGLFramebufferObject::NoAttachment
|
0
|
No attachment is added to the framebuffer object. Note that the OpenGL depth and stencil tests won't work when rendering to a framebuffer object without any depth or stencil buffers. This is the default value. |
QGLFramebufferObject::CombinedDepthStencil
|
1
|
若
GL_EXT_packed_depth_stencil
extension is present, a combined depth and stencil buffer is attached. If the extension is not present, only a depth buffer is attached.
|
QGLFramebufferObject::Depth
|
2
|
A depth buffer is attached to the framebuffer object. |
该枚举在 Qt 4.3 引入或被修改。
另请参阅 attachment ().
这是重载函数。
Constructs an OpenGL framebuffer object of the given width and height based on the supplied format .
这是重载函数。
Constructs an OpenGL framebuffer object of the given size based on the supplied format .
这是重载函数。
Constructs an OpenGL framebuffer object and binds a texture to the buffer of the given width and height .
The
attachment
parameter describes the depth/stencil buffer configuration,
target
the texture target and
internal_format
the internal texture format. The default texture target is
GL_TEXTURE_2D
, while the default internal format is
GL_RGBA8
for desktop OpenGL and
GL_RGBA
for OpenGL/ES.
另请参阅 size (), texture ()，和 attachment ().
这是重载函数。
Constructs an OpenGL framebuffer object and binds a texture to the buffer of the given size .
The
attachment
parameter describes the depth/stencil buffer configuration,
target
the texture target and
internal_format
the internal texture format. The default texture target is
GL_TEXTURE_2D
, while the default internal format is
GL_RGBA8
for desktop OpenGL and
GL_RGBA
for OpenGL/ES.
另请参阅 size (), texture ()，和 attachment ().
这是重载函数。
Constructs an OpenGL framebuffer object and binds a 2D GL texture to the buffer of the given width and height .
Constructs an OpenGL framebuffer object and binds a 2D GL texture to the buffer of the size
size
. The texture is bound to the
GL_COLOR_ATTACHMENT0
target in the framebuffer object.
The
target
parameter is used to specify the GL texture target. The default target is
GL_TEXTURE_2D
. Keep in mind that
GL_TEXTURE_2D
textures must have a power of 2 width and height (e.g. 256x512), unless you are using OpenGL 2.0 or higher.
By default, no depth and stencil buffers are attached. This behavior can be toggled using one of the overloaded constructors.
The default internal texture format is
GL_RGBA8
for desktop OpenGL, and
GL_RGBA
for OpenGL/ES.
It is important that you have a current GL context set when creating the QGLFramebufferObject, otherwise the initialization will fail.
另请参阅 size (), texture ()，和 attachment ().
[虚拟]
QGLFramebufferObject::
~QGLFramebufferObject
()
Destroys the framebuffer object and frees any allocated resources.
Returns the status of the depth and stencil buffers attached to this framebuffer object.
Switches rendering from the default, windowing system provided framebuffer to this framebuffer object. Returns
true
upon success, false otherwise.
另请参阅 release ().
[static]
bool
QGLFramebufferObject::
bindDefault
()
Switches rendering back to the default, windowing system provided framebuffer. Returns
true
upon success, false otherwise.
[static]
void
QGLFramebufferObject::
blitFramebuffer
(
QGLFramebufferObject
*
target
, const
QRect
&
targetRect
,
QGLFramebufferObject
*
source
, const
QRect
&
sourceRect
,
GLbitfield
buffers
= GL_COLOR_BUFFER_BIT,
GLenum
filter
= GL_NEAREST)
Blits from the sourceRect rectangle in the source framebuffer object to the targetRect rectangle in the target framebuffer object.
若
source
or
target
is
nullptr
, the default framebuffer will be used instead of a framebuffer object as source or target respectively.
The
buffers
parameter should be a mask consisting of any combination of
GL_COLOR_BUFFER_BIT
,
GL_DEPTH_BUFFER_BIT
，和
GL_STENCIL_BUFFER_BIT
. Any buffer type that is not present both in the source and target buffers is ignored.
The
sourceRect
and
targetRect
rectangles may have different sizes; in this case
buffers
should not contain
GL_DEPTH_BUFFER_BIT
or
GL_STENCIL_BUFFER_BIT
。
filter
parameter should be set to
GL_LINEAR
or
GL_NEAREST
, and specifies whether linear or nearest interpolation should be used when scaling is performed.
若 source 等于 target a copy is performed within the same buffer. Results are undefined if the source and target rectangles overlap and have different sizes. The sizes must also be the same if any of the framebuffer objects are multisample framebuffers.
Note that the scissor test will restrict the blit area if enabled.
This function will have no effect unless hasOpenGLFramebufferBlit () returns true.
该函数在 Qt 4.6 引入。
另请参阅 hasOpenGLFramebufferBlit ().
Draws the given texture, textureId , to the given target rectangle, target , in OpenGL model space. The textureTarget should be a 2D texture target.
The framebuffer object should be bound when calling this function.
Equivalent to the corresponding QGLContext::drawTexture ().
该函数在 Qt 4.4 引入。
Draws the given texture, textureId , at the given point in OpenGL model space. The textureTarget should be a 2D texture target.
The framebuffer object should be bound when calling this function.
Equivalent to the corresponding QGLContext::drawTexture ().
该函数在 Qt 4.4 引入。
Returns the format of this framebuffer object.
Returns the GL framebuffer object handle for this framebuffer object (returned by the
glGenFrameBuffersEXT()
function). This handle can be used to attach new images or buffers to the framebuffer. The user is responsible for cleaning up and destroying these objects.
[static]
bool
QGLFramebufferObject::
hasOpenGLFramebufferBlit
()
返回
true
if the OpenGL
GL_EXT_framebuffer_blit
extension is present on this system; otherwise returns
false
.
该函数在 Qt 4.6 引入。
另请参阅 blitFramebuffer ().
[static]
bool
QGLFramebufferObject::
hasOpenGLFramebufferObjects
()
返回
true
if the OpenGL
GL_EXT_framebuffer_object
extension is present on this system; otherwise returns
false
.
返回
true
if the framebuffer object is currently bound to a context, otherwise false is returned.
该函数在 Qt 4.5 引入。
返回
true
if the framebuffer object is valid.
The framebuffer can become invalid if the initialization process fails, the user attaches an invalid buffer to the framebuffer object, or a non-power of two width/height is specified as the texture size if the texture target is
GL_TEXTURE_2D
. The non-power of two limitation does not apply if the OpenGL version is 2.0 or higher, or if the GL_ARB_texture_non_power_of_two extension is present.
The framebuffer can also become invalid if the QGLContext that the framebuffer was created within is destroyed and there are no other shared contexts that can take over ownership of the framebuffer.
[override virtual protected]
int
QGLFramebufferObject::
metric
(
QPaintDevice::PaintDeviceMetric
metric
) const
重实现： QPaintDevice::metric (QPaintDevice::PaintDeviceMetric metric) const.
[override virtual]
QPaintEngine
*QGLFramebufferObject::
paintEngine
() const
重实现： QPaintDevice::paintEngine () const.
Switches rendering back to the default, windowing system provided framebuffer. Returns
true
upon success, false otherwise.
另请参阅 bind ().
Returns the size of the texture attached to this framebuffer object.
Returns the texture id for the texture attached as the default rendering target in this framebuffer object. This texture id can be bound as a normal texture in your own GL code.
If a multisample framebuffer object is used then the value returned from this function will be invalid.
Returns the contents of this framebuffer object as a QImage .
The returned image has a format of premultiplied ARGB32 or RGB32. The latter is used only when internalTextureFormat() is set to
GL_RGB
.
If the rendering in the framebuffer was not done with premultiplied alpha in mind, create a wrapper QImage with a non-premultiplied format. This is necessary before performing operations like QImage::save () because otherwise the image data would get unpremultiplied, even though it was not premultiplied in the first place. To create such a wrapper without performing a copy of the pixel data, do the following:
QImage fboImage(fbo.toImage()); QImage image(fboImage.constBits(), fboImage.width(), fboImage.height(), QImage::Format_ARGB32);
On QNX the back buffer is not preserved when a buffer swap occures. So this function might return old content.