#version 450 core
out gl_PerVertex { vec4 gl_Position; };

layout(std140, binding=0) uniform PerFrame { mat4 uView; mat4 uProj; vec4 uLightDir; };
layout(std140, binding=1) uniform PerObject { mat4 uModel; };

layout(location=0) in vec3 aPos;  // XY from grid, Z ignored
layout(location=2) in vec2 aUV;   // 0..1 across the grid

layout(location=0) out VS_OUT {
  vec3 wPos;
  vec2 uv;
} v;

// ---- tiny fBm noise (tile-free, cheap) ----
float hash(vec2 p){ return fract(sin(dot(p, vec2(127.1,311.7))) * 43758.5453); }
float noise(vec2 p){
  vec2 i=floor(p), f=fract(p);
  float a = hash(i + vec2(0,0));
  float b = hash(i + vec2(1,0));
  float c = hash(i + vec2(0,1));
  float d = hash(i + vec2(1,1));
  vec2 u = f*f*(3.0-2.0*f);
  return mix(mix(a,b,u.x), mix(c,d,u.x), u.y);
}
float fbm(vec2 p){
  float a=0.5, s=0.0;
  for(int i=0;i<5;i++){ s += a*noise(p); p = p*2.02 + 17.0; a*=0.5; }
  return s;
}

// tunables
uniform float uHeightScale = 3.0;     // world Z amplitude
uniform float uFreq        = 2.0;     // base frequency (cycles over 0..1 uv)

void main(){
  float h = fbm(aUV * uFreq) * uHeightScale;  // Z-up displacement
  vec3 p  = vec3(aPos.xy, h);
  vec4 w  = uModel * vec4(p,1.0);

  v.wPos = w.xyz;
  v.uv   = aUV;

  gl_Position = uProj * uView * w;
}