I am making my own class diagram app in Swing/AWT but i stopped at this functionality:
I want to draw a line between the Class rectangle that already selected and to the target Class rectangle, but line has a feature which is whenever i move one of the rectangles the line that join them get bend in a straight fashion following the moving rectangle , i hope the following picture demonstrate what i want to achieve:
A general guideline or a sample code is highly appreciated
I don't know Java, but the steps you could follow are these:
Find the middle of each line of the rectangles (should be easy, just avarage x1+x2 and y1+y2)
Determine the edges that are closest to each other using Pythagoras formula on the points you got in the previous step.
Start drawing a line starting at xa,ya (first point you got in the step above), and draw it in the direction away from the rectangle. You should know this direction, because you can know the line segment this point is on.
Do the same for xb,yb (point on the second rectangle). If the lines are in opposite directions, you should draw them to halfway xa-xb or ya-yb (depending on if you're drawing horizontally or vertically). If they are perpendicular (is that the right word?) you should draw them to the point where they cross, so you draw the line from xa,ya to xa,yb or xa,ya to xb, ya, depending if you draw the horizontal or vertical line.
There should be some additional check to see if the rectangles overlap. You should not draw lines in the same direction for example. Maybe it would suffice for you to draw just a diagonal line between the two points in those cases where you cannot determine how to draw these straight lines.
For the implementation you could build a line class that uses the observer pattern to listen to the two rectangles it follows, so it can update itself whenever one of them moves or resizes.
http://java-sl.com/connector.html
Hope this helps.
Try with observer pattern. All lines that are connected with a moving object should be notified with new position of the object and 'bent' properly. Of course, first implement some logic that will connect 2 objects.
try creating a class named "ConnectingLine" or similar. this class will then have several segments (that's the name of these line parts in dia, which is currently my favorite uml modeling tool) which will be calculated one by one. you'll have a sepaparate class for this of course ;) called maybe "LineSegment". i think this should make it easier for you to perform the mathematical calculations required to perform this task.
this could also enable making segments "auto routed or not" easy d(^_^)b
Related
So I'm doing the project of an introduction to Java course and it seems that I chose something that goes way beyond what I'm able to do. :P
Any help would be greatly appreciated. This is what I'm having problems with:
You have a cursor that is controlled by a player (goes forward or
turns 90°) which leaves a colored line as it goes. If you manage to go
over your own line and close a polygon of any shape (only right angles
though), its surface changes color into the color of your line.
I can detect when this situation arises but I am kind of lost as how to actually fill the correct polygon just closed. I can't seem to imagine an algorithm that would cover any case possible.
I looked at the Scanline fill algorithm but I think it would start having problems by the time there are already some polygons already filled in the map.
The Floodfill algorithm would be perfect if I had a way of finding a point inside the polygon, but, as there are many different possibilities, I can't think of a general rule for this.
I'm using an array 2x2 of integers where each color is represented by a number.
Does anyone have an idea on how to approach this problem?
If you can detect the situation then this can be solved in very simple manner. The question is which point to choose as start point for floodfill. The simple answer is: try all of them. Of course it makes a sense to start only with points adjacent to the one where your cursor is located. In this case you will have at most 8 points to check. Even better - at least 2 of them are definitely painted already if current point forms a polygon.
So you have 8 points to check. Launch floodfill 8 times starting from each of those points.
Two things which you probably should keep in mind:
You should try filling the area in cloned version of your field in order to be able to get back if floodfill will not find a polygon.
Launching floodfill second time and later you should reuse this cloned version of your field to see whether it was filled there. This will allow you to check every point at most once and this will make your 8 floodfills almost as fast as 1 floodfill.
Check this question, using Graphics2 and Polygon to fill an arbitrary polygon: java swing : Polygon fill color problem
Finding out whether a point is inside or outside a polygon: http://en.wikipedia.org/wiki/Point_in_polygon
Make sure you use double buffering. If you set individual pixels and don't use double buffering the component may redraw after every pixel was set.
I'm applying the scan-line algorithm to fill in a randomly generated continent-like shape. The main problem I'm having is when the line intersects a point that is a tip. I created some images to help visualize this.
http://i.stack.imgur.com/OlbI5.png
http://i.stack.imgur.com/RACF1.png
I basically need help figuring out how to differentiate if an intersection point is a "tip" or not. Like in the first image, since both are tips, I end up with a line in between them, even though the line is outside of the continent-shape.
try checking to the immediate left and the right of the intersection. If they're both below the red line, than it's a tip.
That's the best i can do without knowing more about how the lines are defined.
I'm trying to draw a flat surface out of voxels, the goal is to draw it filled and I'm having a lot of trouble. Everything I try results in holes on the surface. The surface has 4 corners, but I'd like to be able to use the same method for triangles too.
Here's what I've tried:
Draw along from one parallel side to the other
Draw only in one direction (z direction) along a side of the plane
I've had the most success with 2 but it fails when I add any pitch or roll to the plane (any elevation present).
Any tips? There's no code because I'm sure my implementations are all correct, it's just the choice of algorithm that's wrong.
EDIT:
On a side note, though number 2 had less holes, the planes were distorted and didn't appear flat.
EDIT2:
I'm sticking with my first decision, but now the question is, how do I detect when there will be a hole? By observation I notice there's the same amount of holes per plane regardless of pitch and roll. Yaw is the culprit here.
EDIT3:
I'm leaving this question up but I decided to just test a nearby block to see if it's empty. I didn't want to do it, but yeah. If you have a more elegant solution I'm all ears.
A plane, being infinite, does not have corners. Are you talking about a four-sided polygon? Does it have square corners?
For a polygon, I would certainly start off with a triangle, since you can construct any other polygon out of triangles, not the other way around.
Then, a good start for filling a triangle would probably be to come up with an accurate test of whether a given voxel should be filled or not. Here's an example of two different point-in-triangle tests.
After you have that you can proceed in different ways. For example, although not the most efficient, you could region-grow from the center, testing each neighboring voxel and recursing with a stack.
I'm making a project for college, where I have to make my own primitive vector editor, and I have two questions:
Is it right to make vector line object by saving it's start point coordinates, end point coordinates, color and width of points, which it will consist of? Point is also my class, which is drawn on JPanel.
If it is right, how can I make this line selectable? The only thing I can think of is to check mouse coordinates to be inside of line width.
I also have a restriction not to use any standard functions for drawing lines, splines, etc.
Yes that's right. Or you could represent it in polar coordinates
the best thing to do is actually turn your line into an Area, which implements Shape and thus contains, which is the method you want. Area is a great abstraction because it can represent any shape but everything gets manipulated in the same way.
You can use Line2D Shape. To check selection you can gt stroked Shape from BasicStroke and check whether the stroked Shape contains clicked point.
To Point 1: You also need to save the direction of the vector.
To Point 2: There are some frameworks like GEF which do the job for you. Here you have to change your model. You need two classes: Point and Connection
You can use a class Vector if you have one with start and end Point for do it if you want.
You can have a method like that:
private static Shape generateVector(Point start, Point end)
In this method you can use one object of ´Area´ for build the vector, with Line2D. Tree lines if you want an arrow.
Or you can use a GeneralPath for build it.
For select a particular vector with the mouse, you can get the coordinates, with getX() and getY() on the MouseEvent and ask in the shape object with method contains and repaint with other color.
Good luck!
I'm currently writing an application that actually acts as a "cut" tool for 3D meshes. Well, I had some problems with it now which I am clueless on how to solve, since it is my first application.
I have loaded a model from an object file onto the canvas, then on the same canvas, I use the mouse drag event to draw lines to define the cutting point.
Let us say I want to cut a ball into half and I draw the line in the middle. How do I detect the vertices of the ball under the line.
Secondly, if I rotate/translate the ball, would all the the vertices information change?
Think of what you'd do in the real world: You can't cut a ball with a line, you must use a knife (a line has no volume). To cut the ball, you must move the knife through the ball.
So what you're looking after is a plane, not a line. To get such a plane, you must use some 3D math. What you have is the canvas orientation and the "side view" of the plane (which looks like a line).
So the plane you're looking for is perpendicular to the canvas. A simple way to get such a plane is to take the canvas orientation and create a plane which has the same orientation and then rotate the plane around the line by 90°.
After that, you can visit all edges of your model and determine on which side of the plane they are. For this, determine on which side of the plane the end points of the edge are. Use the cross product. If they are on the same side (both results of the cross products will have the same sign), you can ignore the edge. Otherwise, you need to determine the intersection point of the edge and plane. Create new edges and connect them accordingly.
See this page for some background on the math. But you should find some helper methods for all this in your opengl library.
if I rotate / translate the ball, would all the the vertices information change
Of course.
It's not going to be that easy.
I assume the line you are drawing induces a plane which then cuts the sphere.
To do so, you have to calculate the intersecting area of the sphere and the plane.
This is not a trivial task and I suggest using an existing framework for this or if you really want to do this yourself, read about basic intersection problems to get a feeling for this kind of problem. This paper offers a good introduction to various intersection tests.
In general boundary represended volumes, as in your case, are difficult to handle when it comes to more advanced manipulations. Cutting a sphere in half is easy compared to burring a small hole into it. Sometimes it's better to use a volume representation, like tetrahedral meshes or CSG.
Regarding your second question, you shouldn't rotate or translate the sphere, rotate and translate the camera.