Pixi.js lines are rendered outside dedicated area

问题:

I'd like to draw some kind of popyline chart using pixijs lineTo method. The problem is the lines are rendered outside dedicated area.

Sample:

    var stage = new PIXI.Stage(0xFFFFFE);
    var renderer = new PIXI.WebGLRenderer(600, 600);
    document.body.appendChild(renderer.view);

    var graphics = new PIXI.Graphics();
    graphics.lineStyle(1, 0x0000FF, 1);

    graphics.moveTo(0, 50);
    graphics.lineTo(50, 50);//draw min Y line
    graphics.moveTo(0, 100);
    graphics.lineTo(50, 100);//draw max Y line

    graphics.moveTo(60, 50);
    graphics.lineTo(60 + 0.1, 100);
    graphics.lineTo(60 + 0.2, 50);

    stage.addChild(graphics);
    requestAnimFrame(animate);

    function animate() {
        requestAnimFrame(animate);
        renderer.render(stage);
    }

Result:

Why it happens and how to avoid it?

回答1:

It seems to only occur using the WebGLRenderer with non-integer numbers.

Broken (as per your example):

var renderer = new PIXI.WebGLRenderer(600, 600);
graphics.moveTo(60, 50);
graphics.lineTo(60 + 0.1, 100);
graphics.lineTo(60 + 0.2, 50);

Works (with rounded numbers):

var renderer = new PIXI.WebGLRenderer(600, 600);
graphics.moveTo(60, 50);
graphics.lineTo(60, 100);
graphics.lineTo(60, 50);

Works (with canvas renderer):

var renderer = new PIXI.CanvasRenderer(600, 600);
graphics.moveTo(60, 50);
graphics.lineTo(60 + 0.1, 100);
graphics.lineTo(60 + 0.2, 50);

Fiddle here

You could submit the issue on GitHub, but in the meantime rounding your values to the nearest pixel, or using only the Canvas renderer will solve it.