distance 函数到底从哪里来的

[liyihongcug]

Tools-16PrimitivePoints.js

"varying vec4 v_color;
void main()
{
float d = distance(gl_PointCoord, vec2(0.5,0.5));
if(d < 0.5){
gl_FragColor = v_color;
}else{
discard;
}
}
";

找了半天没有找到这个 distance 到底从哪里来的

[liyihongcug]

在Expression.js

function distance(call, left, right) {
    if (typeof left === 'number' && typeof right === 'number') {
        return Math.abs(left - right);
    } else if (left instanceof Cartesian2 && right instanceof Cartesian2) {
        return Cartesian2.distance(left, right);
    } else if (left instanceof Cartesian3 && right instanceof Cartesian3) {
        return Cartesian3.distance(left, right);
    } else if (left instanceof Cartesian4 && right instanceof Cartesian4) {
        return Cartesian4.distance(left, right);
    }

    throw new RuntimeError('Function "' + call + '" requires vector or number arguments of matching types. Arguments are ' + left + ' and ' + right + '.');
}

[YanzheZhang]

distance是webgl中glsl语言内置函数