#version 330

// Input vertex attributes
in vec3 vertexPosition;
in vec2 vertexTexCoord;
in vec3 vertexNormal;
in vec4 vertexColor;

// Input uniform values
uniform mat4 mvp;
uniform mat4 matModel;

uniform sampler2D texture0;

// Output vertex attributes (to fragment shader)
out vec2 fragTexCoord;
out vec4 fragColor;

// NOTE: Add your custom variables here
out vec3 worldPosition;
out vec3 worldNormal;

void main()
{
    // Send vertex attributes to fragment shader
    fragTexCoord = vertexTexCoord;
    fragColor = vertexColor;

    float l = textureOffset(texture0, vertexTexCoord, ivec2(-1, 0)).x;
    float r = textureOffset(texture0, vertexTexCoord, ivec2(1, 0)).x;
    float u = textureOffset(texture0, vertexTexCoord, ivec2(0, -1)).x;
    float d = textureOffset(texture0, vertexTexCoord, ivec2(0, 1)).x;

    vec3 lr = normalize(vec3(1, 0, r - l));
    vec3 ud = normalize(vec3(0, 1, u - d));

    vec3 normal = normalize(cross(lr, ud));

    vec3 localPos = vertexPosition + vec3(0, texture2D(texture0, vertexTexCoord).x * 0.1, 0);

    // Calculate final vertex position
    gl_Position = mvp*vec4(localPos, 1.0);
    worldPosition = (matModel * vec4(localPos, 1.0)).xyz;
    worldNormal = mat3(matModel) * normal;
}