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.
Related
I would like to draw a grid on a canvas using EaselJS. I am using the new WebGL stage, StageGL.
A grid is basically N times of a horizontal line and M times of a vertical line.
I see multiple options:
Draw N+M lines as all different shapes (I am talking about EaselJS "Shape" instances), cache them (as WebGL needs rasters) and add them to the stage.
Draw 1 horizontal and 1 vertical line, cache them (as WebGL needs rasters) and somehow draw the same image in the stage
Draw a single shape which consists of N+M paths, cache it and add it to the stage.
Option #1 seems naive to me. They're all the same image, why drawing them to the cache N+M times?
Option #2 would solve the problem in option #1, but I don't know how to do it.
Option #3 results in a very large image. For N=50, M=50 and gridSpacing=50px, it would result in a 2500x2500 px image. I don't know if this is ideal.
Which one is the best approach?
Are there any other approaches? I don't think I am the first person who draws a grid :)
You can pretty easily cache a shape, and use the resulting cache (canvas) as the source for a Bitmap.
var shape = new createjs.Shape();
shape.graphics.drawStuff();
// Since shapes have no bounds, you will have to know the bounds based on what you draw:
shape.cache(x, y, w, h);
var bmp = new createjs.Bitmap(shape.cacheCanvas);
You can draw as many of these Bitmaps without any additional cost, since its the same source canvas/image. EaselJS StageGL (latest NEXT, released shortly hopefully) renders this in WebGL no problem.
Check out the SpriteSheetBuilder demo and docs in GitHub to draw content to a SpriteSheet/Sprite instead of a Bitmap.
Cheers.
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 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.
This question already has an answer here:
Can I get vector data back out out of a Graphics object?
(1 answer)
Closed 9 years ago.
EDIT (for clarification):
I have a vector image with a simple contour, an irregular closed polygon.
I need to import it into Flash in a way that I can then programmatically access each of the segments that form the polygon.
Importing the vector image into the library as a MovieClip wasn't good because all I get is a shape from which I can take no geometry information at all.
My goal is being able to calculate the polygon's area and also calculating the intersection between the polygon and another polygon.
I guess I could write an Illustrator script that reads all the segments and writes a CSV files with their coordinates, but there has to be a simpler way, I mean, they're both vectorial, they should understand each other.
Thanks!
.
-- Old Post: --
I have a contour in vector graphics that I imported to the Flash library as a movieclip.
I Instanciate the movieclip and it has a Shape child which is the actual contour.
I need to be able to access the contour segments, i.e. the polygon's sides, to be able to get their starting and ending points, is there a way?
the Graphics class only allows to draw but what you draw, as with the Shape class, are not objects, it's not a polygon with sides or whatever.
Am I being clear?
Thanks
There is no way to read the data of a Graphics object (which is essentially what contains the information that you are after.) This applies to any vector graphics object that has already been drawn, either by the Graphics/drawing API itself, or in Flash CS3/CS4, or was embedded using the [Embed] meta-tag.
Your best bet if you need to calculate the algebraic area, or for some other reason retain the vectors in your algorithms, is definitely exporting an SVG or some single-purpose format (like a CSV of the points) from Illustrator, and parsing that in ActionScript.
Another option is to use a BitmapData, and draw the Shape object onto that, then counting the colored (opaque) pixels to numerically calculate it's area.
var bmp : BitmapData = new BitmapData(myShape.width, myShape.height, true, 0);
bmp.draw(myShape);
var i : uint;
var area : uint = 0;
var num_pixels : uint = bmp.width*bmp.height;
for (i=0; i<num_pixels; i++) {
var px : uint = bmp.getPixel32(i%bmp.width, Math.floor(i/bmp.height));
// Determine from px color/alpha whether it's part of the shape or not.
// This particular if statement should determine whether the alpha
// component (first 8 bits of the px integer) are greater than zero, i.e.
// not transparent.
if ((px >> 24) > 0)
area++;
}
trace('number of opaque pixels (area): '+area);
Depending on your application, you might also be able to use the BitmapData.hitTest() method for your collision detection.
I believe the best you can do is to retrieve a rectangular bounding box on the Shape object. Depending on how you imported it, you may or may not have direct access to the Shape object as an instance variable; however, if you do, you can call shapeVar.transform.getBounds() or shapeVar.transform.getRect() (bounds returns a rectangle inclusive of strokes on the shape, rect does not).
I'm curious, so I'm doing a bit of research on alternate means of getting some pixel bounds. I'll edit this further if I find something useful.