i am not really newbie in Qt, but there are a few things i don't know...
I am programming in Python, but feel free to post your answers in ANY language.
So, i have a few QGraphicsItem (s), positioned inside a QGraphicsScene, the scene is viewed with a normal QGraphicsView. Everything is normal.
My scene is very large, 10,000 x 10,000 pixels, all graphic items are scattered around.
For example :
# Creating Scene object.
scene = QtGui.QGraphicsScene()
scene.setSceneRect(0, 0, 10000, 10000)
# Creating View object.
view = QtGui.QGraphicsView()
view.setScene(scene)
# Adding some objects to scene.
# scene.addItem(...)
# ...
# The list of items.
items = scene.items()
# This is how i center on item.
view.centerOn(some_item)
view.fitInView(some_item, Qt.KeepAspectRatio)
My question is, how can i center the view on every item, using something similar to centerOn, but smoothly ?
Currently, centerOn goes FAST on next item, i want to move it slooowly, maybe using QPropertyAnimation with easing curve ?
I tried to move the view to the next item using view.translate(1, 1) in a big cicle, but the movement is too fast, just like centerOn.
I tried to put some waiting with time.sleep(0.01) between the translating, but the windows blocks untill the cicle exists... so it's bad.
Thank you very much !
I once used a QTimeLine (with EaseInOutCurve), connected it to a slot, and then used that value to translate the view rect, like this:
const QRectF r = ...calculate rect translated by timeline value and trajectory...
view->setSceneRect( r );
view->fitInView( r, Qt::KeepAspectRatio );
For the trajectory I used a QLineF with start and end position for the smooth scrolling.
Then one can use the value emitted by timeline nicely with QLineF::pointAt().
In my case I needed to set both SceneRect and fitInView to make it behave like I wanted.
I solved my problem by placing a high value on setSceneRect. Then I centralize the scene on an object or position.
example:
this->ui->graphicsView->setSceneRect (0,0,100000000, 100000000);
this->ui->graphicsView->centerOn(500,1030);
With the setSceneRect size GraphicsView does not work right.
Related
I draw few rectangles inside the QGraphicsView ; I use custom stipple pattern for these by creating a QBrush with my QPixmap. This gets displayed with the default zoom level as expected.
When I call view->scale(), the rectangles show up bigger or smaller as I expected. However Qt has scaled the individual bits of the stipple pattern which is not expected; I expected it to draw the larger or smaller rectangle again with the brush.
Eg.
If I had used a stipple pattern with one pixel dot and pixel space, after zooming in, I want to see a larger rectangle but I want the same stipple pattern with same pixel gaps. Is this achievable somehow? Thanks.
I ran into the same problem while developing an EDA tool companion in Qt.
After some trying, what I did (and seems to work for me) is to create a custom graphics item. On the paint method, I do:
QBrush newBrush = brush_with_pattern;
newBrush.setTransform(QTransform(painter->worldTransform().inverted()));
painter->setBrush(newBrush);
That is to apply the inverse transformation of the item to the brush (so it does not scale).
I think that the setDashOffset is only for the border of the shapes (not the fill).
You may use QPen::setDashOffset:
http://harmattan-dev.nokia.com/docs/library/html/qt4/qpen.html#setDashOffset
You'll need to set the offset based on the scenes zoom/scale level. You can grab a pointer to the scene in your item by calling scene(), don't forget to check for NULL though since it will be NULL when not added to the scene (although you shouldn't in theory get a paint() when not in a scene).
The other option is to use:
http://doc.qt.digia.com/qt/qpainter.html#scale
To undo the views scaling on your painter.
In case anyone is still looking on this, a related question here regarding scaling of standard fill patterns instead of pixmap fill patterns may help. Basically, it may not be possible to modify scaling of standard fill patterns (a few workaround ideas are listed), but, working with alpha values instead gives the desired effect if you are looking for varying colors, especially gray levels - and is much less convoluted.
Whats is the best way of creating a line (QGraphicsLineItem) which starts at some point on the scene and continues to infinity at some angle.
The way I presently do this is by calculating were the line intersects the view and drawing the line segment.
Is there a better way?
Could I for example set the lines length to some massive number?
You could define its paint() and shape() functions so they always use all the space available and needed inside the scene, i.e. inside the visible part of qgraphicsview.
Guidelines:
Examine mapping functions for qgraphicsview, qgraphicsscene and
qgraphicsitem (mapToScene, mapToItem, mapToView or something like that)
Define your shape() and paint() functions as if your
line is exactly long all over the view (by using the mapping functions above)
So, how ever the user moves his view, repaint will examine the space used by qgraphicsview and draw exactly that long. The illusion is created that the line goes on-and-on.
I'm working on a Qt based application (actually in PyQt but I don't think that's relevant here), part of which involves plotting a potentially continuous stream of data onto a graph in real time.
I've implemented this by creating a class derived from QWidget which buffers incoming data, and plots the graph every 30ms (by default). In __init__(), a QPixmap is created, and on every tick of a QTimer, (1) the graph is shifted to the left by the number of pixels that the new data will take up, (2) a rectangle painted in the space, (3) the points plotted, and (4) update() called on the widget, as follows (cut down):
# Amount of pixels to scroll
scroll=penw*len(points)
# The first point is not plotted now, so don't shift the graph for it
if (self.firstPoint()):
scroll-=1
p=QtGui.QPainter(pm)
# Brush setup would be here...
pm.scroll(0-scroll, 0, scroll, 0, pm.width()-scroll, pm.height())
p.drawRect(pm.width()-scroll, 0, scroll, pm.height())
# pen setup etc happens here...
offset=scroll
for point in points:
yValNew = self.graphHeight - (self.scalePoint(point))
# Skip first point
if (not(self.firstPoint())):
p.drawLine(pm.width()-offset-penw, self.yVal, pm.width()-offset, yValNew)
self.yVal = yValNew
offset-=penw
self.update()
Finally, the paintEvent simply draws the pixmap onto the widget:
p = QtGui.QPainter(self)
p.drawPixmap(0, 0, self.graphPixmap)
As far as I can see, this should work correctly, however, when data is received very fast (i.e. the entire graph is being plotted on each tick), and the widget is larger than a certain size (approx 700px), everything to the left of the 700px area lags considerably. This is perhaps best demonstrated in this video: http://dl.dropbox.com/u/1362366/keep/Graph_bug.swf.html (the video is a bit laggy due to the low frame rate, but the effect is visible)
Any ideas what could be causing this or things I could try?
Thanks.
I'm not 100% sure if this is the problem or not, but I thought I might make at least some contribution.
self.update() is an asynchronous call, which will cause a paint event at some point later when the main event loop is reached again. So it makes me wonder if your drawing is having problems because of the sync issue between when you are modifying your pixmap vs when its actually getting used in the paintEvent. Almost seems like what you would need for this exact code to work is a lock in your paintEvent, but thats pretty naughty sounding.
For a quick test, you might try forcing the event loop to flush right after your call to update:
self.update()
QtGui.QApplication.processEvents()
Not sure that will fix it, but its worth a try.
This actually might be a proper situation to be using repaint() and causing a direct paint event, since you are doing an "animation" using a controlled framerate: self.repaint()
I noticed a similar question to yours, by someone trying to graph a heart monitor in real time: http://qt-project.org/forums/viewthread/10677
Maybe you could try restructuring your code similar to that. Instead of splitting the painting into two stages, he is using a QLabel as the display widget, setting the pixmap into the QLabel, and painting the entire graph immediately instead of relying on calls to the widget.update()
So basically when I try to draw more a mesh inside an FBX file its orientation is always removed and it's scaled down. I'm not sure if the issue is caused by code or the way I'm exporting the FBX files. I have been trying to narrow down the cause and I am fairly sure it's not caused by the way I export the FBX (but I could be wrong), so it's either the XNA content pipeline or my drawing code
Here are some pics I took to show my problem, where the gray background is in 3Ds Max as I see it and red background is in XNA:
THis is as it appears in 3D StudioMax: http://i.stack.imgur.com/e0oW4.png
This is how it appears in XNA: http://i.stack.imgur.com/1vOcx.png
Both are being viewed from the same angle and direction but varying distances.
Now what is really odd is if I create another mesh in max, say a box, and export that (along with the original model), it works fine: http://i.stack.imgur.com/SIDg9.png
So long as there is more than one mesh in the fbx model it draws properly (though I'm still suspicious if it's drawing with proper scaling applied, i.e. if in Max it is 1 unit long in XNA it becomes something like 1.27 units long), if there is less its orientation which I applied to it in 3D studio max is removed when I draw it.
This is how I draw the model:
model.CopyAbsoluteBoneTransformsTo(boneTransforms);
foreach (ModelMesh mesh in model.Meshes)
{
foreach (BasicEffect effect in mesh.Effects)
{
effect.World = boneTransforms[mesh.ParentBone.Index];
Vector3 cameraPosition = Camera.Get.Position;// new Vector3(0, 0, 0);
//cameraPosition.X = -Camera.Get.PosX;
//cameraPosition.Y = Camera.Get.PosY;
effect.View = Camera.Get.View;// Matrix.CreateLookAt(cameraPosition, cameraPosition + Camera.Get.LookDir, Camera.Get.Up);
effect.Projection = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4,
BaseGame.Get.GraphicsDevice.Viewport.AspectRatio,
0.01f, 1000000); //Matrix.CreateOrthographic(800 / 1, 480 / 1, 0, 1000000);
//effect.TextureEnabled = true;
effect.LightingEnabled = true;
effect.PreferPerPixelLighting = true;
//effect.SpecularColor = new Vector3(1, 0, 0);
}
mesh.Draw();
}
Obviously mesh.draw() is called twice when there is more than one mesh in the fbx file..
Generally if you are having a problem with the position or scale of the mesh while rendering, then it's likely to be related to the matrices. Not necessarily the exporting, but rather how you use them in the code.
I use blender3d for modelling, but I know that Blender3d actually defines different spaces when you are creating the meshes within the editor. For example, if you create a mesh while in 'object' mode, the position/rotation/scale of the object in the scene will not be exported (because that object will be the root of a new tree, centered around 0,0,0). So I would check for a similar situation in 3DMax - make sure you are transforming the vertices in Max relative to 0,0,0, or else you may lose the 'initial' translation and when you render in XNA, all the objects will be rendered around your 0,0,0 (i.e. appear mixed together).
Failing that, and I can't remember exactly off the top of my head, but I think you may need to multiply the current mesh's absolute matrix transform with that of the parent's world matrix transform. Although it's been a while so I'm not too sure.
I've got a small action-script chart, that's meant to be live updating, and also be able to support more than 10000 points of data. The way it's currently set up it doesn't need to redraw the whole chart if the new line we wish to add doesn't extend that chart's boundaries.
Yet it does, the redraw regions show the whole chart as being redrawn as opposed to the single line i need to add.
When the chart gets a new piece of data from the javascript it does the following.(some stuff has been stripped for clarity.
private function registerJSCallbacks() : void
{
ExternalInterface.addCallback( "addData", addData );
}
private function addData( val : * ) : void
{
trace( "addData",val );
var g: Graphics = this.graphics;
g.moveTo(x1,y1);
g.lineTo(x2,y2);
}
Is there any better way to do that, that won't redraw the whole screen? Is my coding pattern wrong for this type of update?
I'm a novice so even vaguely relevant advice would be appreciated.
You're editing the underlying vector, so it has to redraw the whole thing. You've got a couple options:
(easiest): Spawn a new Sprite after every X draw operations, so that each draw only recalculated a few vector lines
(more involved): Use one Sprite to draw, and every X draw operations, write the graphics in the sprite to a backing BitmapData object (using bitmapData.draw) and clear the sprite.
Option 2 is probably performs better than option 1, but I haven't benchmarked this specific scenario. You might get comparable performance if you sprite.cacheAsBitmap = true on each Sprite in option 1 as you move to a new "active" sprite.