I am using the 3d framework min3d and am trying to draw a rectangle that covers the whole screen. What parameters should I pass to the constructor of the Rectangle class?? It is declared this way:
public Rectangle(float $width, float $height, int $segsW, int $segsH, Color4 color)
I don't see what are segsH and segsW for. I can't see any doc about the constructor.
I got it, it didn't have anything to do with those parameters. By default the rectangle is drawn completely perpendicular to the screen so you can't see it. If you want to see it with the same dimensions you drew it you have to rotate it in y axis. Example:
rect = new Rectangle(1, 1, 2, 2,new Color(255,0,0,255));
rect.rotation().y = 180;
rect.lightingEnabled(false);
scene.addChild(rect);
In case this is usefull for someone else =)
It appears segsW and segsH control how many triangles are used to draw the rectangle.
Related
I am playing around with an application that draws and traces the user's finger on the canvas. See this picture, the green rectangle was drawn by tracing the user's finger motion. I took most of the code from the old FingerPaint application from the android SDK samples. The gist of it is to draw a Path on a canvas with:
canvas.drawPath (path, paint)
My first challenge was to redraw the path correctly when the screen changes. For example, when the phone gets rotated from vertical to horizontal, the image gets resized and I have to redraw the path along the correct coordinates. I was able to correctly do that with transform. I used the path.transform(matrix) to translate the coordinates of the path.
My next challenge now is to properly scale the thickness of the line. When I draw the path, the thickness of line is set with setStrokeWidth. For example, I set the thickness to 12:
paint.setStrokeWidth(12);
I don't know how to properly scale the thickness of the line when the screen changes. Would anynone know how to do that ?
A suggestion would be to first save the canvas and the path as a bitmap and then redraw the bitmap on the new screen dimensions. But I don't want to do that because I want to support a undo/redo operations where the user can undo/redo the paths that were traced on the canvas.
you can use sth like this:
float screenWidthPixel = this.getResources().getDisplayMetrics().widthPixels;
float screenHeightPixel = this.getResources().getDisplayMetrics().heightPixels;
float STROKE_WIDTH = screenWidthPixel * 0.0035f;
float Y_POSITION = screenHeightPixel * 0.01f;
paint.setStrokeWidth(STROKE_WIDTH);
I am a newbie learner to JBox2D. I was just trying JBox2D for the first time on Android(I know Android development and I'm good in it) because my project needed physics.
Now, the tutorials and "Official User Manual" of Box2D said that negative gravity would result in objects being attracted downwards. But, in my case the object is being attracted upwards when I set Vec2's second parameter to be negative! Weird.
Here's the code which results in a circle shape going up on its own:
The Gravity:
Vec2 gravity = new Vec2(0.0f, -50.0f);
boolean doSleep = true;
world = new World(gravity, doSleep);
The circle shape is being made by following code:
//body definition
BodyDef bd = new BodyDef();
bd.position.set(200, 500);
bd.type = BodyType.DYNAMIC;
//define shape of the body.
CircleShape cs = new CircleShape();
cs.m_radius = 10f;
//define fixture of the body.
FixtureDef fd = new FixtureDef();
fd.shape = cs;
fd.density = 1f;
fd.friction = 0.2f;
fd.restitution = 0.8f;
//create the body and add fixture to it
body = world.createBody(bd);
body.createFixture(fd);
And I'm using SurfaceView canvas to draw:
canvas.drawCircle(body.getPosition().x, body.getPosition().y, 10, paint);
And stepp-ing as follows:
float timeStep = 1.0f / 60.f;
int velocityIterations = 6;
int positionIterations = 2;
world.step(timeStep, velocityIterations, positionIterations);
So, what's wrong within my code? I am unable to identify the mistake I've done.
Also,
I'm making a tennis-like 2D game on Android for which I'll be using JBox2D. So, can anybody tell me a tutorial/book on JBox2D? Though I googled vigorously, I couldn't find a good tutorial on it. (Though Box2D seems to be much popular instead of JBox2D)
I would be extremely grateful if someone could help me out here. Thank you.
In Box2D there is standard coordinate system: Y directed up, X to the right. In the graphic systems, usual, coordinate system has Y directed down, because window has static top-left corner. Looks like at your graphic system all the same. So, what in Box2D is moving down, you see as moving up.
It is the irritable problem, and directing gravity up is not the best solution. If you change only gravity, then you will need think about up-down problem in many other cases, for example, when define bodies, apply forces and so on. The most irritable, that it is not easy to understand, how physic coordinates conform graphic (for example, in one of my projects I had to draw points on paper, then turn paper back, rotate on 180 grades and look on the light :).
You can't change Box2D coordinate system, but, most likely, you can easy change coordinate system of graphic system by changing translation matrix. For example, in OpenGL it looks like this:
glScalef(1.0, -1.0, 1.0);
But take attention, after this, all that have positive Y coordinate will be not visible on the screen (it will be above the top edge of the window). So, you will need work with negative coordinates. If you don't want this, you can translate matrix down like this:
glTranslatef(0.0, -windowHeight.0, 0.0)
But before, think what to do if window would be resized.
About second question. I doubt whether you can find anywhere tutorial or book for JBox2D. JBox2D is port of Box2D (that means, it is exact copy of Box2D), and writing special book for it looks strange. Learn Box2D, and you will have no problem with JBox2D. For example, you can look there.
I'm trying to create a 'glow' effect using the Android Path class. However, the gradient is not being warped to fit around the path. Instead, it is simply being display 'above' it and clipped to the path's stroke. Using a square path, the image below shows what I mean:
Instead, that should look more like this:
In other words, the gradient follows the path, and in particular wraps around the corners according to the radius set in the CornerPathEffect.
Here is the relevant part of the code:
paint = new Paint();
paint.setStyle(Style.STROKE);
paint.setStrokeWidth(20);
paint.setAntiAlias(true);
LinearGradient gradient = new LinearGradient(30, 0, 50, 0,
new int[] {0x00000000, 0xFF0000FF, 0x00000000}, null, Shader.TileMode.MIRROR);
paint.setShader(gradient);
PathEffect cornerEffect = new CornerPathEffect(10);
paint.setPathEffect(cornerEffect);
canvas.drawPath(boxPath, paint);
Any ideas?
Another alternative is to get a 'soft-edged brush' effect when defining the stroke width. I've experimented with BlurMaskFilters, but those give a uniform blur rather than a transition from opaque to transparent. Does anyone know if that's possible?
How about drawing with a soft brush bitmap? Make a soft circular brush with opacity decreasing radially outward using image editing software like Photoshop. Save as drawable, load it in a bitmap and draw it evenly spaced along your path. Make the bitmap with white coloured brush. This way you can simply multiply the given colour(Here blue) to your bitmap using PorterDuffColorFilter.
brush1=BitmapFactory.decodeResource(getResources(), R.drawable.brush_custom_one);
//This contains radially decreasing opacity brush
porter_paint.setColorFilter(new PorterDuffColorFilter(paint.getColor(), Mode.MULTIPLY));
for (int i=1;i<matrix.size();i++) {
//matrix contains evenly spaced points along path
Point point = matrix.get(matrix.get(i));
canvas.drawBitmap(brush1, point.x,point.y, porter_paint);}
The brush used is (It's there):
The final result is:
Turns out there was a stupidly obvious way of doing this. Simply re-use the same path, and adjust the stroke width and alpha on each drawing pass. Example code:
float numberOfPasses = 20;
float maxWidth = 15;
for (float i = 0; i <= numberOfPasses; i++){
int alpha = (int) (i / numberOfPasses * 255f);
float width = maxWidth * (1 - i / numberOfPasses);
paint.setARGB(alpha, 0, 0, 255);
paint.setStrokeWidth(width);
canvas.drawPath(path, paint);
}
See below for an example of the result. The left path was drawn using this method, the right path, for comparison, is drawn in a single stroke with maxWidth and 255 alpha.
This mainly works. There are two problems:
The gradient isn't as smooth as it could be. This is because each pass being drawn over the previous one results in the alpha building up too quickly, reaching 255 before the final strokes. Experimenting a bit with the line int alpha = (int) (i / numberOfPasses * 125f); (note the change to 125f rather than 255f) helps.
The path looks like it has been 'cut' on the insides of the corners. Probably some result of the CornerPathEffect applied.
What you're wanting to do, if I understand it right, is to have the gradient effectively form a "brush" for the stroke.
This is exactly what I also was trying to achieve recently, but as far as I can tell the API doesn't provide any straightforward means to do it. I have recently created an SVG to Android Canvas converter class and so I am working a lot in Inkscape lately, too. So, when I was looking into it, I wondered if it's even possible to do it in Inkscape. However, even in Inkscape it's a very non-trivial thing to do. After some searching I eventually came across this image of a gradient being applied along the course of a path, together with a download link for a tutorial beneath:
http://www.flickr.com/photos/35772571#N03/3312087295/
What I was personally trying to do at the time was to create some semi-circles where the path is a kind of neon glow as opposed to a flat colour. Talking in terms of both the Android API and the SVG standard, it seems that the only way to to do this is to create a radial gradient that's centred perfectly on the circle, and position a series of color stops in exactly the right places. Pretty tricky to do, and I certainly don't know how you'd do it to a shape like a square.
Sorry that this is a bit of a 'I couldn't do it either' rather than a useful answer! I'll follow this with interest as I'm eager to know a solution for a kind of 'soft brush' effect too.
Can be very complicated to draw a gradient than follow a path.
So I suggest you to use some library already done than make it for you.
One can be Sc-Gauges.
Have some usefully classe than you can use for your goal.
For first include the library:
dependencies {
...
compile 'com.github.paroca72:sc-gauges:3.0.7'
}
After create an image or what you want with a canvas where draw:
<ImageView
android:id="#+id/image"
android:layout_width="match_parent"
android:layout_height="match_parent"
/>
Now the code:
// Dimensions
int padding = 24;
Rect drawArea = new Rect(padding, padding, 700 - padding, 500 - padding);
// Get the main layout
ImageView imageContainer = (ImageView) this.findViewById(R.id.image);
assert imageContainer != null;
// Create a bitmap and link a canvas
Bitmap bitmap = Bitmap.createBitmap(
drawArea.width() + padding * 2, drawArea.height() + padding * 2,
Bitmap.Config.ARGB_8888
);
Canvas canvas = new Canvas(bitmap);
canvas.drawColor(Color.parseColor("#f5f5f5"));
// Create the path building a bezier curve from the left-top to the right-bottom angles of
// the drawing area.
Path path = new Path();
path.moveTo(drawArea.left, drawArea.top);
path.quadTo(drawArea.centerX(), drawArea.top, drawArea.centerX(), drawArea.centerY());
path.quadTo(drawArea.centerX(), drawArea.bottom, drawArea.right, drawArea.bottom);
// Feature
ScCopier copier = new ScCopier();
copier.setPath(path);
copier.setColors(Color.RED, Color.GREEN, Color.BLUE);
copier.setWidths(20);
copier.draw(canvas);
// Add the bitmap to the container
imageContainer.setImageBitmap(bitmap);
And this the result:
The first part of the code is just for create a bitmap where draw.
What you interest is the second part where use ScCopier.
Just give the path, the color and the with.
Note than is you are inside a view you can use onDraw for draw directly on the view canvas.
This library can used to create gauge of every kind.
If you want take a look to this site ScComponents have some free and not gauges components.
I want to create a speech balloon type shape, where there is a rectangle or ellipse with a triangular shape jutting out of it.
How I'm attempting to do this is to create a Path object that combines the triangle with the other shape (round rect).
I'm doing it as follows:
Path path = new Path();
// Create triangular segment
Point drawOffset = getAttributes().getDrawOffset();
int leaderGap = getAttributes().getLeaderGapWidth();
// Recall that we have a coordinate system where (0,0) is the
// bottom midpoint of the annotation rectangle.
// the point to left of gap
int x1 = -leaderGap/2;
int y1 = 0;
// the point to right of gap
int x2 = leaderGap/2;
int y2 = 0;
// The point where we're drawing to; the end of the pointy segment of triangle
int x3 = -drawOffset.x;
int y3 = drawOffset.y;
path.moveTo(x2, y2);
path.lineTo(x3, y3);
path.lineTo(x1, y1);
// path.close();
// Add the rectangular portion to the path
path.addRoundRect(backgroundShape, 5, 5, Path.Direction.CW);
The problem is that the roundRect is a closed path, so its edge shows through underneath the triangular section.
A picture's worth a thousand words, so here you go:
What I want is for the line segment between those two endpoints of the triangle to disappear, so that it looks like one seamless path.
If all I were doing were a straight rectangle, I could create the whole path myself from scratch. But I'd like to do the rounded corners, and it'd be a bit of a paint to do that with the Path (yes I know you can do quad to and arcTo but it's still not as clean a solution as I'd like).
So in general, is it possible to combine two paths and create a single union object that traces the perimeter of both?
Yes this is possible as of API 19. You can perform logical operations between 2 paths. As in your case, you can create a UNION of the two paths, using Path.op(). For a complete list of the operations that can be performed refer here.
I can't see a convenient way to combine paths in this manner. I would normally achieve this by manually drawing the rounded rectangular parts with Path.arcTo() and Path.lineTo(), it's a little extra effort but it will achieve the result you are looking for.
Another option which is perhaps more flexible if you decide to change the theme is to use a ninepatch drawable there's even an editor to let you create them called Draw 9-patch
When I call drawCircle (ex. canvas.drawCircle(x, y, r, mPaint);) and I use Paint Style STROKE to initialize the parameter mPaint, the result doesn't quite make a full 360 degrees (2*PI radian) circle in all cases. Sometimes you get a full circle (as I would expect) and sometimes only an arc.
Does someone have an idea what would cause this to happen ?
I don't know what cases work and which don't (yet). I've noticed the ones that don't work seem to be the larger circles I'm drawing (>100.0 radius). Could be size related. I am using floating point for x, y and r. I could try rounding to the nearest int when in the drawing code.
Are you doing anything else to the canvas before the drawCircle? This could happen if, for example you are scaling the canvas or transforming it before you draw the circle.