spg-project/resources/particles.gs

#version 430

layout (points) in;
layout (triangle_strip, max_vertices = 3) out;

uniform mat4 proj;
uniform mat4 view;

in float varFade[];
in vec3 varOffsetA[];
in vec3 varOffsetB[];

out float varFadeG;

void main(void) {	
    vec4 base = gl_in[0].gl_Position;

    gl_Position = proj * view * vec4(base.xyz, 1.0);
    varFadeG = varFade[0];
    EmitVertex();

    gl_Position = proj * view * vec4(base.xyz + varOffsetA[0], 1.0);
    varFadeG = varFade[0];
    EmitVertex();

    gl_Position = proj * view * vec4(base.xyz + varOffsetB[0], 1.0);
    varFadeG = varFade[0];
    EmitVertex();

    EndPrimitive();
}