#version 450 core

layout(quads, fractional_even_spacing, cw) in;

in TC_OUT {
    vec3 position;
    vec2 texCoord;
} te_in[];

layout(location = 0) uniform mat4 M;

layout(std140, binding = 0) uniform SceneUniforms
{
    mat4 PV;	//camera projection * view matrix
    vec4 eye_w;	//world-space eye position
};

out vec3 fragPosition;

layout(binding = 0) uniform sampler2D heightTexture;
uniform float displacementScale = 0.1;

void main() {
    // Interpolate texture coordinates
    vec2 texCoord = mix(
        mix(te_in[0].texCoord, te_in[1].texCoord, gl_TessCoord[0]),
        mix(te_in[3].texCoord, te_in[2].texCoord, gl_TessCoord[0]),
        gl_TessCoord[1]
    );

    // Interpolate the original position
    vec3 position = mix(
        mix(te_in[0].position, te_in[1].position, gl_TessCoord[0]),
        mix(te_in[3].position, te_in[2].position, gl_TessCoord[0]),
        gl_TessCoord[1]
    );

    fragPosition = (PV*M*vec4(position, 1.0)).xyz;
    gl_Position = PV*M*vec4(position, 1.0f);
}










// layout(quads, equal_spacing, ccw) in;  // Define the type of patch (e.g., quads)
// in vec2 tcs_uv[];

// layout(binding = 0) uniform sampler2D heightTexture;

// layout(location = 0) uniform mat4 M;

// layout(std140, binding = 0) uniform SceneUniforms
// {
//     mat4 PV;	//camera projection * view matrix
//     vec4 eye_w;	//world-space eye position
// };

// in VertexData {
//     vec2 tex_coord;
// } inData[];

// out vec3 frag_position;  // Ensure this matches the input in fragment.glsl

// out VertexData {
//     vec2 tex_coord;
// } outData;

// float getHeight(vec2 uv) {
//     return texture(heightTexture, uv).r;
// }

// void main()
// {
//     const float u = gl_TessCoord[0];
//     const float v = gl_TessCoord[1];
    
//     vec2 tess_coord = gl_TessCoord.xy;
//     vec2 base_uv = mix(tcs_uv[0], tcs_uv[1], tess_coord.x);
//     base_uv = mix(base_uv, mix(tcs_uv[3], tcs_uv[2], tess_coord.x), tess_coord.y);
//     vec4 htex = texture(heightTexture, base_uv);

//     const vec4 p0 = PV*M*gl_in[0].gl_Position;
//     const vec4 p1 = PV*M*gl_in[1].gl_Position;
//     const vec4 p2 = PV*M*gl_in[2].gl_Position;
//     const vec4 p3 = PV*M*gl_in[3].gl_Position;

//     vec4 a = mix(p0, p1, u);
//     vec4 b = mix(p3, p2, u);
//     vec4 c = mix(a, b, v);

//     c.y = htex.r * 0.5f;

//     float eps = 0.0002;
//     float hCenter = getHeight(base_uv);
//     float hRight = getHeight(base_uv + vec2(eps, 0.0));
//     float hLeft = getHeight(base_uv - vec2(eps, 0.0));
//     float hUp = getHeight(base_uv + vec2(0.0, eps));
//     float hDown = getHeight(base_uv - vec2(0.0, eps));

//     vec3 tangentX = normalize(vec3(0.002, hRight - hLeft, 0.0));
//     vec3 tangentZ = normalize(vec3(0.0, hUp - hDown, 0.002));

//     vec3 d0 = gl_in[0].gl_Position.xyz;
//     vec3 d1 = gl_in[1].gl_Position.xyz;
//     vec3 d2 = gl_in[2].gl_Position.xyz;

//     vec3 n_u = d1 - d0;
//     vec3 v_u = d2 - d0;
//     vec3 v_normal = normalize(cross(n_u, v_u));

//     vec3 normal = cross(tangentZ, tangentX);

//     gl_Position = c;
//     outData.tex_coord = base_uv;
//     // outData.pw = vec3(c);
//     // outData.nw = normal;

//     // Interpolate the position using the barycentric coordinates from tessellation
//     // vec3 pos = mix(mix(gl_in[0].gl_Position.xyz, gl_in[1].gl_Position.xyz, gl_TessCoord.x),
//     //                mix(gl_in[3].gl_Position.xyz, gl_in[2].gl_Position.xyz, gl_TessCoord.x),
//     //                gl_TessCoord.y);
    
//     // frag_position = pos;

//     // outData.tex_coord = mix(mix(inData[0].tex_coord, inData[1].tex_coord, gl_TessCoord.x),
//     //                         mix(inData[3].tex_coord, inData[2].tex_coord, gl_TessCoord.x),
//     //                         gl_TessCoord.y);

//     // gl_Position = PV*M*vec4(pos, 1.0);
// }