#version 430
precision highp float;

layout(binding = 0) uniform sampler2D heightTexture;
layout(location = 1) uniform float time;

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

layout(std140, binding = 1) uniform LightUniforms
{
    vec4 La;	//ambient light color
    vec4 Ld;	//diffuse light color
    vec4 Ls;	//specular light color
    vec4 light_w; //world-space light position
};

layout(std140, binding = 2) uniform MaterialUniforms
{
    vec4 ka;	//ambient material color
    vec4 kd;	//diffuse material color
    vec4 ks;	//specular material color
    float shininess; //specular exponent
};

in vec3 frag_position;

in VertexData {
    vec2 tex_coord;
} inData;

out vec4 frag_color; //the output color for this fragment    

void main(void)
{   
    //Compute per-fragment Phong lighting
    // vec4 ktex = texture(diffuse_tex, inData.tex_coord);
        
    // vec4 ambient_term = ka*ktex*La;

    // const float eps = 1e-8; //small value to avoid division by 0
    // float d = distance(light_w.xyz, inData.pw.xyz);
    // float atten = 1.0/(d*d+eps); //d-squared attenuation

    // vec3 nw = normalize(inData.nw);			//world-space unit normal vector
    // vec3 lw = normalize(light_w.xyz - inData.pw.xyz);	//world-space unit light vector
    // vec4 diffuse_term = atten*kd*ktex*Ld*max(0.0, dot(nw, lw));

    // vec3 vw = normalize(eye_w.xyz - inData.pw.xyz);	//world-space unit view vector
    // vec3 rw = reflect(-lw, nw);	//world-space unit reflection vector

    // vec4 specular_term = atten*ks*Ls*pow(max(0.0, dot(rw, vw)), shininess);

    // fragcolor = ambient_term + diffuse_term + specular_term;


    float height = texture(heightTexture, inData.tex_coord).r;

    //frag_color = vec4(inData.tex_coord, 0.0f, 1.0f);

    // if (height > 0.8) frag_color = vec4(vec3(1.0f-height), 1.0f);
    // else frag_color = vec4(vec3(height), 1.0f);
    frag_color = vec4(height, height, height, 1.0);
}