layout (points) in;
layout (triangle_strip) out;
layout (max_vertices = 4) out;

// OF handled uniforms and attributes.
uniform mat4 projectionMatrix;

uniform float u_time;

// App specific uniforms and attributes.
// uniform float uSpriteSize;

in vec4 vPosition[];
in vec4 vPrevPosition[];
in vec2 vTexCoord[];
flat in int vValid[];

out vec2 texCoordVarying;
in vec3 vPos[];
in vec4 vTarget[];
in float vTemperature[];
in float vAge[];

// out vec2 gTexCoord;
out vec3 gPos;
out vec4 gTarget;
out float gTemperature;
out float gAge;

void main()
{
  float uSpriteSize = 1;
  // if (vValid[0] == 0) return;

  texCoordVarying = vTexCoord[0];
  gPos = vPos[0];
  gTarget = vTarget[0];
  gTemperature = vTemperature[0];
  gAge = vAge[0];


  for (int i = 0; i < gl_in.length(); ++i)
  {
    vec3 vOffset = (vPrevPosition[i].xyz - vPosition[i].xyz) * 4;
    vOffset += normalize(vOffset) * 10;
    // if(length(vOffset) < 4) {
    //   vOffset = normalize(vOffset) * 4;
    // }
    vec4 shiftPos = vec4(vOffset, 1) + vPosition[i];

    gl_Position = projectionMatrix * (vPosition[i] + vec4(0.0, 1.0, 0.0, 0.0) * uSpriteSize);
    EmitVertex();

    if (u_time > 10) { // hack
      gl_Position = projectionMatrix * (shiftPos + vec4(0.0, 1.0, 0.0, 0.0) * uSpriteSize);
      EmitVertex();

      gl_Position = projectionMatrix * (vPosition[i] + vec4(0.0, -1.0, 0.0, 0.0) * uSpriteSize);
      EmitVertex();

      gl_Position = projectionMatrix * (shiftPos + vec4(0.0, -1.0, 0.0, 0.0) * uSpriteSize);
      EmitVertex();
    }


    EndPrimitive();
  }
}