I'm using Qt3D with a combination of this offscreen renderer and modified the framegraph to include a background image, like here.
Unfortunately, adding transparency to the objects drawn over the background image using QPhongAlphaMaterial only works unsatisfactorily.
This is th result:
What you can't see here is that the whole circle part is actually transparent, i.e. the renderer wrote the transparency value of the object for the whole pixel instead of adding it transparently on top of the background.
This is what the rendered object looks like wihtout transparency:
And this is the background:
The framegraph has two branches: one for the backgroun image, which is processed first, and one for the objects. I added a QRenderStateSet for the objects that contains a QBlendEquation with the blend function set to add and a QBlendEquationArguments with source RGB and alpha set to 1, and destination RGB and alpha set to 1 minus source alpha.
Any ideas how to fix this problem?
(For anyone wondering, I took the images from the T-Less dataset and wrote a program to create ground-truth data for 6D pose estimation)
Similarly to this question, the format of the texture that is being rendered to needs to be set to RGB8_UNorm and not RGBA8_UNorm, i.e. without the alpha channel.
Related
I have two FBOs created using QOpenGLFrameBufferObject, which are images with a transparent background and some lines and text on top of them. I am blitting the first fbo onto the second using QOpenGLFramebufferObject::blitFramebuffer, this results in the content of the first fbo on top of the second. However, I would like to preserve the transparency of the the first fbo and blend the content of the first fbo on top of the second fbo (instead of erasing the portion of the second fbo and redrawing the first fbo on top of it). Looking around, I think this might be possible with glBlendFunc, but the following didn't really achieve the result I wanted.
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
// then blit fbo1 on top of fbo2
QOpenGLFramebufferObject::blitFramebuffer(fbo2, fbo1);
How can I preserve the transparency (by blending them together) of my framebuffers when I blit them?
You can't glBlitFramebuffer is a copy operation, and does not blend the source and target fragments.
A possibility is to render to a texture (see Framebuffer Object - Attaching Images). Finally you can render a screen space rectangle and Blend the texture with the target framebuffer.
I was trying to add some transparency to a text and oddly enough I noticed it was only transparent on one side while being opaque on the other.
The expected behavior was transparent on both sides. Any idea why this happens?
Thank you.
https://aframe.io/docs/0.8.0/components/material.html#transparency-issues
With opacity, A-Frame sets three.js renderer to sortObjects: false. Transparency ordering is based on when objects are added / defined in the scene. Shuffle the order of the text in like the HTML or when they are injected and it should work.
I have a transparent QGraphicsWebview inside a QGraphicsView with the following settings:
The QGraphicsView is the high level widget, and is shown in full screen mode
The graphics view uses a QGLWidget as its view port (to use opengl-es)
Alpha channel and double buffering are enabled in this QGLWidget
Transparency is achieved by graphicsView->setStyleSheet("background:transparent")
Following attributes are set for QGraphicsView and QGraphicsWebview
WA_TranslucentBackground = true
WA_NoSystemBackground = true
WA_OpaquePaintEvent = false
The QPalette::Base and QPalette::Window brushes of webview and webview->page() are set to Qt::transparent
At the beginning, the transparency works fine. But as the screen get updated (when I scroll), it looks like the new bitmap is blended on top of the existing one to get a superimposed picture. After about 5-6 screen updates, this blending causes the colors to accumulate and form an opaque rectangle (with a corrupted image). Following images show first, second and final stages of the problem.
How do I tell qt/opengl to stop blending and just draw the new image to the frame buffer?
I tried calling fillRect(boundRect(), Qt::transparent) from overridden Webview::paint and GraphicsView::paintEvent; but it didn't work except for making the updates slower.
I am new to Qt and OpenGl, so I might be missing some basic flags or settings.
I tried all the methods mentioned above. They did not work for me. I then debugged into qtbase code and found that setting the Opacity level make the top browser layer transparent.
this->setOpacity(0.1);
this pointer points to the QGraphicsWebView object.
With this method, the whole front browser contents including background will be transparent. To separate header, paragraph and background and to specify different transparent levels for them, I will have to dig into webkit code a little further to figure out the problem. But for now, setOpacity() did the trick and is good enough for what I am doing.
It turns out the problem is graphicsView->setStyleSheet("background:transparent");. Who would have guessed?!
Yeah, the line that I thought made transparency work was actually causing troubles with transparency. The application works fine without that line (or if you change it to background:none)
In short, steps to get a transparent QGraphicsWebview using QGLWidget:
Set the Base palettes of QGraphicsWebview, QWebpage and the outer QGraphicsView to Qt::transparent
scene->setBackgroundBrush(QBrush(Qt::transparent));
You should also make sure that html body background is set to transparent values:
html, body {
background-color: rgba(127, 127, 0, 0.5);
}
I am new to RRDtool. I generated a graph with grid(--grid-dash 1:0), a LINE(LINE1:rt#4e9a06) and I also have the area between the line and the x-axis coloured (AREA:rt#4e9a06 ). I notice the grid still shows up in the colored-area. I am wondering if there is any way to cover the grid with the colored-area.
Also, I am also wondering if there is any good-looking rrdtool samples/examples available online? Thanks.
I have no way of testing this currently, but here's what the documentation says (emphasis mine) :
[-c|--color COLORTAG#rrggbb[aa]]
Override the default colors for the standard elements of the graph.
The COLORTAG is one of BACK background, CANVAS for the background of
the actual graph, SHADEA for the left and top border, SHADEB for the
right and bottom border, GRID, MGRID for the major grid, FONT for the
color of the font, AXIS for the axis of the graph, FRAME for the line
around the color spots, and finally ARROW for the arrow head pointing
up and forward. Each color is composed out of three hexadecimal
numbers specifying its rgb color component (00 is off, FF is maximum)
of red, green and blue. Optionally you may add another hexadecimal
number specifying the transparency (FF is solid). You may set this
option several times to alter multiple defaults.
What about making an almost transparent grid with arguments like these (note the extra 7F parameter which translates to 127 in decimal):
-c MGRID#<hex triplet>7F -c GRID#<hex triplet>7F
It should still be visible in the background but be invisible (or barely noticeable) once any graph covers it.
Note that this answer from the developer of RRDTool says that the grid is always painted after the graph, so in the end you'll always have it in the foreground, your only solution is to either totally disable it or tinker with color/transparency parameters to make it invisible when covered by the graphed data.
I have a image declared like the following:
[Bindable]
[Embed( source="assets/banana.png" )]
public var iconBANANA : Class;
It is involving into itemRenderer, but I wish to change the color of the image when some event occurs (like clicking above or something).
The rest of the objects used the image shall remain unchanged, only the object on which the event has occurred shall change the color of the image.
But the biggest question is :
How to change the image color mainly - like there is a Blue area on image - to turn it on Green, or Yellow ?
I believe what you're looking for are Filters. What you're explaning (changing one color to another) is not exactly trivial and going into some fairly complex image manipulation but you can get some results using the ColorMatrixFilter.
You're looking for beginBitmapFill.