Libgdx gl10.glLineWidth()

问题

I have this line: Gdx.gl10.glLineWidth(width); Now, I do intend to draw a pretty thick line, and, unfortunately when I type in small values like 1 or 5 the line is obviously small. But once I surpass soemthing like 10, it no longer gets larger. I am passing in direct values in these instances, and so, I am under the impression that GL has a limit or something.... Would I be correct? Here's my code:

Gdx.gl.glClearColor(0,0,0,1);
    Gdx.gl.glClear(GL10.GL_COLOR_BUFFER_BIT);

    batch.setProjectionMatrix(cam.combined);
    batch.begin();
    batch.draw(bg,0,0,WIDTH,HEIGHT);
    for(Spell a : spells){
        a.draw(batch);
    }
    lc.draw(batch);
    batch.end();
    //((ppux+ppuy)/2f)*4
    Gdx.gl10.glLineWidth(50);//average and then say 1/4 a unit)
    renderer.setProjectionMatrix(cam.combined);
    renderer.begin(ShapeType.Line);
    lp.drawLines(renderer);
    renderer.end();
    batch.begin();
    lp.draw(batch);
    batch.end();

lp.drawLines(renderer) calls the following(I just call set color, and draw line):

renderer.setColor(1,1,1,1);
    Elem a = elems.get(spellcombo.get(0));
    Vector2 last = new Vector2(a.x(),a.y());
    for(int i = 1; i < spellcombo.size(); i++){
        a = elems.get(spellcombo.get(i));
        Vector2 cur = new Vector2(a.x(),a.y());
        renderer.line(last.x, last.y, cur.x, cur.y);
        last = cur;
    }
    renderer.line(last.x,last.y,mx,my);
    Gdx.gl.glEnable(GL10.GL_BLEND);
    Gdx.gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);
    renderer.setColor(1, 0, 0, .2f);
    for(Elem e : elems){
        int id = elems.indexOf(e);
        if(ComboManager.validSpell(spellcombo,id))
            renderer.line(last.x,last.y,e.x(),e.y());
    }

Screenshots:
Image with glLineWidth() set to 1

Image with glLineWidth() set to 5

Image with glLineWidth() set to 10

Image with glLineWidth() set to 20

Image with glLineWidth() set to 200

I don't really know how to fix, and google wasn't particularily helpfull. Thanks!

回答1:

In Libgdx the Gdx.gl10 object is the wrapper for the OpenGL 1.x API. So, the calls there are all (basically) calls into OpenGL ES (on Android) or regular OpenGL (on the desktop). Sometimes the Java layer makes changes to the API, but generally its a pretty straightforward mapping. (On the Desktop, Libgdx tries to emulate the ES variant so the API presented contains only ES-relevant APIs.)

The line-drawing support in OpenGL ES is one place where ES changes from regular OpenGL. Both have limitations on supported line width, though in regular OpenGL the limitations seem to apply only to anti-aliased lines.

Regular OpenGL

http://www.opengl.org/sdk/docs/man/xhtml/glLineWidth.xml

There is a range of supported line widths. Only width 1 is guaranteed to be supported; others depend on the implementation. To query the range of supported widths, call glGet with argument GL_ALIASED_LINE_WIDTH_RANGE.

OpenGL ES

http://www.khronos.org/opengles/sdk/docs/man/xhtml/glLineWidth.xml

There is a range of supported line widths. Only width 1 is guaranteed to be supported; others depend on the implementation. To query the range of supported widths, call glGet with argument GL_ALIASED_LINE_WIDTH_RANGE.

To query the limits in Libgdx, use something like this:

int[] results = new int[1];
Gdx.gl10.glGetIntegerv(GL20.GL_ALIASED_LINE_WIDTH_RANGE, results, 0);

The upshot of all of this though, is that because line drawing (other than width 1.0) on OpenGL ES has different run-time limitations on different platforms, you probably should use a different scheme (like rectangles) to draw fat lines.

回答2:

From libgdx 1.0 on there is also the ShapeRenderer's rectLine method available. See a simple example.

ShapeRenderer shapeRenderer = new ShapeRenderer();
shapeRenderer.begin(ShapeType.Filled);
shapeRenderer.rectLine(x1, y1, x2, y2, width);
shapeRenderer.end();

That seems to be the easiest way to draw thick lines now.

来源：https://stackoverflow.com/questions/16680908/libgdx-gl10-gllinewidth

标签

java

libgdx