Why EndPrimitive function sometimes does not work?

Question

Problem

Sometimes EndPrimitive function in OpenGL's geometry shaders does not work as I expected- few output primitives are joined together.

Details

Program

I want to draw a shape that consists of lines on each multiplication of given angle and distant from given center (given minimum radius and maximum radius). I am trying to write a geometry shader that takes information about a star:

Star.hpp

struct Star{
    QVector3D center;
    QVector3D color;
    GLfloat thickness;
    GLfloat repAngle__deg;
    GLfloat radiusMin;
    GLfloat radiusMax;
};

I am passing the data as Point in VBO. The geometry shader looks like this:

star.geom

#version 330

layout(points) in;
layout(line_strip, max_vertices = 360) out;

in VS_OUT{
    vec3 color;
    float thickness;
    float repAngleDegrees;
    float radiusMin;
    float radiusMax;
} gs_in[];

out vec3 fColor;

uniform mat4 matrix;

const float PI = 3.1415926;

void main()
{
    if(gs_in[0].thickness > 0){
        for(float angle = 0; angle < 360; angle += gs_in[0].repAngleDegrees){
            float angleRad = PI*angle/180;

            float cosVal = cos(angleRad);
            float sinVal = sin(angleRad);

            float minR = gs_in[0].radiusMin;
            float maxR = gs_in[0].radiusMax;

            vec4 minOffset = vec4(cosVal * minR, -sinVal * minR, 0.0, 0.0);
            gl_Position = matrix * (gl_in[0].gl_Position + minOffset);
            fColor = gs_in[0].color;
            EmitVertex();

            vec4 maxOffset = vec4(cosVal * maxR, -sinVal * maxR, 0.0, 0.0);
            gl_Position = matrix * (gl_in[0].gl_Position + maxOffset);
            fColor = gs_in[0].color;
            EmitVertex();
            EndPrimitive();
        }
    }
}

If I pass more than one "Points" (structures that describes a star I want to draw) there are some unwanted connections between returned primitives as shown in .

The screenshot was taken while rendering data:

Star s;
s.center = {0,0,0};
s.color = {0,0.7,0.1};
s.thickness = 1;
s.repAngle__deg = 15;

QVector<Star> vec;
s.repAngle__deg = 15; s.radiusMin = 25; s.radiusMax = 125; 
vec.append(s); 

s.repAngle__deg = 30; s.radiusMin = 20; s.radiusMax = 125; 
vec.append(s); 

s.repAngle__deg = 90; s.radiusMin = 15; s.radiusMax = 125; 
vec.append(s); 

_vboStars.allocate(vec.constData(), vec.count() * sizeof(Star));

where _vboStars is a QOpenGLBuffer.

and:

from data:

    s.repAngle__deg = 10; s.radiusMin = 5; s.radiusMax = 10; vec.append(s); 
    s.repAngle__deg = 15; s.radiusMin = 15; s.radiusMax = 20; vec.append(s); 
    s.repAngle__deg = 30; s.radiusMin = 25; s.radiusMax = 30; vec.append(s); 
    s.repAngle__deg = 60; s.radiusMin = 35; s.radiusMax = 40; vec.append(s); 
    s.repAngle__deg = 90; s.radiusMin = 45; s.radiusMax = 50; vec.append(s); 

I think there is a problem in geometryShader, but I can't find the problem. I've tried also with returning triangle strips (line as 2 triangles) - got same the results.

Observations

• sometimes it works just fine
• it is stable (does not change between frames)
• usually, there are unwanted connections only between few primitives (not all from one input point)
• unwanted connections were not spotted for first input point (usually, they occur for second input point)

My ideas

1. Maybe there is a problem with output limitations?
2. Driver issue?
3. Probably it's my misuse

Environment

• Qt 5.5
• OpenGL
  • OpenGL vendor string: Intel Open Source Technology Center
  • OpenGL renderer string: Mesa DRI Intel(R) Haswell Desktop
  • OpenGL core profile version string: 3.3 (Core Profile) Mesa 10.6.5