//决定片元着色器的颜色
varying vec3 vColor;
uniform float time;
uniform float size;
attribute vec3 color;
attribute vec3 oldColor;
attribute vec3 toPositions;
attribute vec3 oldPositions;
attribute float toPositionsDuration;
// attribute float scale;

void main() {
    vec3 dispatchPos;
    //顶点位置移动
    //当前时间在点的运行时间中占比 0 -> 1
    float percent = time / toPositionsDuration;
    //用min限制 最大不超过1 
    percent = min(percent, 1.);
    dispatchPos = oldPositions + percent * (toPositions - oldPositions);
    vColor = oldColor + percent * (color - oldColor);
    //旋转
    vec4 modelPosition = modelMatrix * vec4(dispatchPos, 1.0);
    float angle = atan(modelPosition.x, modelPosition.z);
    float distanceToCenter = length(modelPosition.xy);
    float angleOffset = (4.0 / distanceToCenter) * time * 0.7;
    angle += angleOffset;
    modelPosition.x = cos(angle);
    modelPosition.z = sin(angle);

    dispatchPos.xz += modelPosition.xz;
    vec4 viewPosition = modelViewMatrix * vec4(dispatchPos, 1.0);

    gl_Position = projectionMatrix * viewPosition;
    //PointsMaterial材质的size属性和每个粒子随机的缩放 大小不一效果
    // gl_PointSize = size * scale;
    gl_PointSize = size;

    //近大远小效果 值自己调节
    gl_PointSize *= (120. / -(modelViewMatrix * vec4(dispatchPos, 1.0)).z);
}