在Java中从边缘和顶点绘制地图

Question

Given a large amount of vertices and edges. The vertices are given x and y coordinates and every edge will have two vertices.

For zooming, the easy solution is to just draw all the edges that have a vertex in the given x and y coordinate, that the screen is zoomed in on, instead of drawing every single edge on the map. But how will I draw the edges that just run through the area that I am zoomed in on?

The only solution I can come up with is to linearly go through every edge and calculate whether the edge will enter the area I am zoomed in on, by finding the x and y coordinate for each end of the edge. Does anyone have a sneaky solution to this?

Also, regarding panning, would the best solution not be to load 8 boxes around the area, that the user sees, with the same size?

EDIT: I forgot to say, the different edges have information in them, so according to each zoom level, different types of edges will be drawn, which is why I prefer to make my own zoom.

Answer 1

So you want to do it with Java but you didn't tell what graphics library you want to use. When drawing is getting more complicated and intensive like in your example you should use something more sophisticated like OpenGL instead of thinking of calculating a zoom by yourself. To use it with Java, there is a wrapper library: JOGL .

OpenGL provides the tools to draw vertices and shapes and you use a camera to organize the view and zoom.

So first I suggest to get familiar with graphics programming (and it doesn't really matter in which programming language or with which library).

I found these tutorials helpful:

• Basic JOGL tutorials
• JOGL in Netbeans

Update

• OpenGL is perfectly suitable for drawing 2D (as you will learn in the tutorials).
• Especially if your things to draw change according to zoom level a graphics library is useful because the whole scene will be rendered at least every time the content changes. You can simply check the zoom level before rendering and draw things according to it.