#version 150 core
#extension GL_ARB_tessellation_shader: require

layout(quads, equal_spacing, ccw) in;

in block {
    vec3 pos;
    vec3 color;
} In[];

out block {
    vec3 pos;
    vec3 color;
} Out;

void main() {
    vec3 tessellated_pos = mix(
        mix(In[0].pos, In[1].pos, gl_TessCoord.x),
        mix(In[3].pos, In[2].pos, gl_TessCoord.x),
        gl_TessCoord.y);

    vec3 v_Color = mix(
        mix(In[0].color, In[1].color, gl_TessCoord.x),
        mix(In[3].color, In[2].color, gl_TessCoord.x),
        gl_TessCoord.y);

    // just pass through to Geometry stage
    Out.pos = tessellated_pos;
    Out.color = v_Color;
}