I'm not sure I'm following you. From what you described, following the technique of the DeclarativeChart class will likely be the simple road since you have everything already working with a QGraphicsScene. You don't render the QImage to a texture, your render your scene on a QImage and then you make a texture of it. Qt already supports creating texture from QImage.
I tested it with different options what brought me to following: Using QQuickPaintedItem and painting scene content or its part in overloaded paint method gives the same effects like rendering to QImage and using it as a texture.
But when QQuickPaintedItem has set:. Qt Forum. Only users with topic management privileges can see it. Hi All, Happy New Year!
Could someone describe it more. Some general concept of that. Reply Quote 0 1 Reply Last reply. Hi, The general concept is that the scene is rendered in a QImage that is then converted to a texture to be used by the node. See the renderScene and updatePaintNode functions. Hope it helps. Reply Quote 1 1 Reply Last reply. But please correct me if I'm wrong.
Do You mean this one with rendering QImage into texture? Ok, I understood a point but I'm mixing terminology Thank You a lot for the answer. Thanks for the feedback. Loading More Posts 11 Posts. Reply Reply as topic.On most platforms, the rendering will occur on a dedicated thread. Communication between the item and the renderer should primarily happen via the QQuickFramebufferObject::Renderer::synchronize function.
This function will be called on the render thread while the GUI thread is blocked. To render into the FBO, the user should subclass the Renderer class and reimplement its Renderer::render function. The Renderer subclass is returned from createRenderer. The size of the FBO will by default adapt to the size of the item. Starting Qt 5. Warning: This class is only suitable when working directly with OpenGL. It is not compatible with the RHI-based rendering path.
This property controls if the size of the FBO's contents should be mirrored vertically when drawing. This allows easy integration of third-party rendering code that does not follow the standard expectations. When this property is false, the FBO will be created once the first time it is displayed.
If it is set to true, the FBO will be recreated every time the dimensions of the item change. Documentation contributions included herein are the copyrights of their respective owners.
Qt and respective logos are trademarks of The Qt Company Ltd. All other trademarks are property of their respective owners. Detailed Description On most platforms, the rendering will occur on a dedicated thread. Using queued connections or events for communication between item and renderer is also possible.
Both the Renderer and the FBO are memory managed internally. Property Documentation mirrorVertically : bool This property controls if the size of the FBO's contents should be mirrored vertically when drawing. The default value is false.
This property was introduced in Qt 5. Access functions: bool mirrorVertically const void setMirrorVertically bool enable. This function will be called on the rendering thread while the GUI thread is blocked.Friday July 15, by Yoann Lopes Comments. As mentioned in that article, one of the new features is a new technique for text rendering based on distance field alpha testing.
This technique allows us to leverage all the power of OpenGL and have text like we never had before in Qt: scalable, sub-pixel positioned and sub-pixel antialiased Now, most of you are probably wondering what a distance field is. Also known as distance transform or distance map, it is a derived representation of a digital image that maps each pixel to a value representing the distance to the closest edge of the glyph.
On a range from 0. A distance field can be generated either from a high-resolution image or from a vector-based representation of the glyph. The first solution is typically based on a brute-force method and can potentially be very slow, thus it is hardly conceivable to use this solution in our case when we have dozens of glyphs or even hundreds in the case of Chinese to generate at once.
Some tools like this one allow to pre-render a set of glyphs from a given font into a file to be then used at run-time, but we didn't choose this solution as it gives poor flexibility to developers. We chose instead to use a vector-based representation of the glyph to generate the distance data.
Put simply, we extrude the outline of the glyph by a fixed distance on the inside and on the outside and fill the area between the extruded outlines with a distance gradient. We store the result in a single 8-bit channel of a 64x64 pixels cell contained in a bigger texture. By doing so we manage, thanks to Kim, to generate a distance field in less than a millisecond per glyph on a mobile device on averagemaking any vector font usable dynamically at run-time.
This technique allows to take advantage of the native bilinear interpolation performed by the GPU on the texture. The distance from the edge can be accurately interpolated, allowing to reconstruct the glyph at any scale factor. All we need to do is alpha-testing: pixels are shown or discarded depending on a threshold, typically 0. The result is a glyph with sharp outlines at any level of zoom, as if they were vector graphics.
The only flaw is that it cuts off sharp corners, but this is negligible considering how bad a magnified glyph looks when this technique is not used.
This technique provides a great visual improvement while not affecting performance at runtime as everything is done "for free" by the graphics hardware.Qt Tutorial : C++ Notepad App
Using the same distance field representation of the glyph, we can also do high-quality anti-aliasing using a single line of shader code:. Instead of using a single threshold to do alpha-testing, we now use two distance thresholds that the shader uses to soften the edges.
The input distance field value is interpolated between the two thresholds with the smoothstep function to remove aliasing artifacts. The width of the soft region can be adjusted by changing the distance between the two thresholds. The more the glyph is minified, the wider the soft region is. The more the glyph is magnified, the thinner the soft region is. When the GPU is powerful enough meaning desktop GPUs we can even do sub-pixel anti-aliasing, it is just about adding some lines of shader code.
Instead of using the distance data to compute the output pixel's alpha, we use the data of the neighboring pixels to compute each color component of the output pixel separately.
Five texture samples are then needed instead of one. The red component averages the three left-most distance field values, the green component averages the three middle distance field values and the blue component averages the three right-most distance field values. Because this requires more processing power, sub-pixel anti-aliasing is currently disabled on mobile platforms. Anyway, the high pixel density displays that equips mobile devices nowadays make the use of sub-pixel anti-aliasing pointless.
In addition to anti-aliasing, the distance field can be used, again with just a few lines of shader code, to do some special effects like outlining, glows or drop shadows. We are then able to implement the three styles provided by the QML Text element outline, raised and sunken using that technique.Welcome back! Last time we talked about texturing, lighting and geometry in regards to porting fixed function OpenGL to Modern OpenGL and while it covered the basic features in OpenGL programs, it left out a lot of advanced techniques that your fixed-function code may have used.
Render to texture is used in a variety of graphical techniques including shadow mapping, multi-pass rendering and other advanced visual effects. It involves taking the results of one rendering pass and using those produced pixels as a texture image in another rendering pass.
There a few ways you could have done this in your fixed-function applications:. Pixel buffer pbuffers for short are fixed-function off-screen memory areas on the video card that replace the normal back-buffer as the destination for rendering.
In normal rendering there is a font-buffer, a back-buffer, a depth buffer and optionally a stencil buffer allocated for you when you create the OpenGL graphics context associated with your window. This default set of buffers is called the window-system-provided framebuffer. What a pbuffer does is provide another set of buffers to use as a destination for the pixel data created when you render with OpenGL.
Pbuffer support falls into the category of an OpenGL extension. With these two extensions you now can render an image to the pbuffer off-screen memory on your video card. The question becomes; how can you use it in your next rendering pass as a texture image? What this extension does is let you describe the type of texture image pixel format and texture-target that you want your off-screen pbuffer to be used for.
With these three extensions we have everything we need to create a copy-free fixed-function render-to-texture application.
The following procedure describes exactly how to use the APIs in these extensions to perform render-to-texture.
Distance Field... Huh?
When you use pbuffers you also must use separate rendering contexts one for each pbuffer and that brings along a host of issues since you now have to manage two or more completely separate OpenGL states.
A FBO is a complete description of a set of compatible with each other off-screen rendering surfaces, including up 8 or more color-surfaces, a depth buffer surface, and a stencil surface. You pretty much get everything you had with pbuffers but with the big difference of besides having multiple color surfaces having it all done in the single OpenGL context associated with your window.
This means there is no context-switch overhead and no need to manage separate OpenGL states. We already know that a FBO contains a set of framebuffer-attachable images, but exactly what are they?
Qt Documentation Snapshots
There are off-screen memory buffers on the video card that can be used as the target and source of pixels produced and consumed when rendering in OpenGL. There are two types of framebuffer-attachable images; texture images and renderbuffer images.
You use texture images when you want to use the resulting pixels as a texture in a later rendering pass and renderbuffer otherwise. Each of these framebuffer-attachable images is assigned a specific attachment position in the containing framebuffer object. Doing this should be preferred over creating multiple FBOs, assigning a static set of image buffers and then switching between those FBOs.
You use glBindframeBuffer to make that frame buffer the target for active rendering. You use glGenRenderbuffers to create render-buffer object, glBindRenderbuffer to make it active, and glRenderbufferStorage to actually create the off-screen memory buffer. You use glFramebufferRenderbuffer and glFrameBufferTexture2D to attach previously created render-buffer or texture-images to a framebuffer object. Each attachment point itself must be complete according to these rules.
Empty attachments attachments with no image attached are complete by default. If an image is attached, it must adhere to the following rules:. Notice that there is no restriction based on size. The effective size of the FBO is the intersection of all of the sizes of the bound images ie: the smallest in each dimension.The AbstractTexture class shouldn't be used directly but rather through one of its subclasses.
Each subclass provides a set of functors for each layer, cube map face and mipmap level. In turn the backend uses those functor to properly fill a corresponding OpenGL texture with data. It is expected the functor does as minimal processing as possible so as not to slow down textures generation and upload.
If the content of a texture is the result of a slow procedural generation process, it is recommended not to implement this directly in a functor. All textures are unique. If you instantiate twice the same texture this will create 2 identical textures on the GPU, no sharing will take place. Holds the current texture handle, if Qt 3D is using the OpenGL renderer, handle is a texture id integer. Documentation contributions included herein are the copyrights of their respective owners.
Qt and respective logos are trademarks of The Qt Company Ltd. All other trademarks are property of their respective owners. Contents Properties Detailed Description. Import Statement: import Qt3D. Render 2. Holds the current texture handle type. Constant Value AbstractTexture. NoHandle AbstractTexture.In the common case of simply using a QImage as the source of texture pixel data most of the above steps are performed automatically.
Another option would be to transform your texture coordinates. This enum specifies which comparison operator is used when texture comparison is enabled on this texture. It stores an OR combination of Feature values. For more information on creating array textures, see Array Texture.
This enum defines the possible texture formats. Depending upon your OpenGL implementation only a subset of these may be supported. Creates a QOpenGLTexture object that can later be bound to the 2D texture target and contains the pixel data contained in image. If you wish to have a chain of mipmaps generated then set genMipMaps to true this is the default. This does create the underlying OpenGL texture object.
Therefore, construction using this constructor does require a valid current OpenGL context. This does not create the underlying OpenGL texture object. Therefore, construction using this constructor does not require a valid current OpenGL context. Allocates server-side storage for this texture object taking into account, the format, dimensions, mipmap levels, array layers and cubemap faces.
Once storage has been allocated for the texture then pixel data can be uploaded via one of the setData overloads. Note: If immutable texture storage is not available, then a default pixel format and pixel type will be used to create the mutable storage. You can use the other allocateStorage overload to specify exactly the pixel format and the pixel type to use when allocating mutable storage; this is particulary useful under certain OpenGL ES implementations notably, OpenGL ES 2where the pixel format and the pixel type used at allocation time must perfectly match the format and the type passed to any subsequent setData call.
See also isStorageAllocated and setData. However, if immutable texture storage is not available, then the specified pixelFormat and pixelType will be used to allocate mutable storage; note that in certain OpenGL implementations notably, OpenGL ES 2 they must perfectly match the format and the type passed to any subsequent setData call. Binds this texture to the currently active texture unit ready for rendering. Binds this texture to texture unit unit ready for rendering.
If parameter reset is true then this function will restore the active unit to the texture unit that was active upon entry.
Writes the texture border color into the first four elements of the array pointed to by border. Returns the textureId of the texture that is bound to the target of the currently active texture unit.
Returns the textureId of the texture that is bound to the target of the texture unit unit. Returns the texture comparison operator set on this texture. By default, a texture has a CompareLessEqual comparison function. Returns the texture comparison mode set on this texture. By default, a texture has a CompareNone comparison mode i. Creates the underlying OpenGL texture object. This requires a current valid OpenGL context.This property specifies whether the texture should be mirrored when loaded.
This is a convenience to avoid having to manipulate images to match the origin of the texture coordinates used by the rendering API. By default this property is set to true. This has no effect when using GPU compressed texture formats. Warning: This property results in a performance price payed at runtime when loading uncompressed or CPU compressed image formats such as PNG. To avoid this performance price it is better to set this property to false and load texture assets that have been pre-mirrored.
Note: OpenGL specifies the origin of texture coordinates from the lower left hand corner whereas DirectX uses the the upper left hand corner. Note: When using cube map texture you'll probably want mirroring disabled as the cube map sampler takes a direction rather than regular texture coordinates.
Documentation contributions included herein are the copyrights of their respective owners. Qt and respective logos are trademarks of The Qt Company Ltd. All other trademarks are property of their respective owners. Contents Properties Detailed Description. Import Statement: import Qt3D. Render 2.