feat: add contour-based multi-octave bump mapping for rougher terrain

shaders/simple.frag

@@ -9,10 +9,12 @@ void main() {
     // ambient component
     float ambientStrength = 0.1;
     vec3 ambient = ambientStrength * vColor.rgb;
-    // bump mapping perturbation
-    float bumpStrength = 0.2;
-    float nVal = fract(sin(dot(vNormal.xy, vec2(12.9898, 78.233))) * 43758.5453);
-    vec3 bumpNormal = normalize(vNormal + bumpStrength * (nVal - 0.5));
+    // terrain bump mapping with multi‐octave noise based on world position
+    float bumpStrength = 0.4;
+    float n1 = fract(sin(dot(vPosition.xz, vec2(12.9898, 78.233))) * 43758.5453);
+    float n2 = fract(sin(dot(vPosition.xz * 0.5, vec2(93.9898, 67.345))) * 24634.6345);
+    float noiseVal = mix(n1, n2, 0.5);
+    vec3 bumpNormal = normalize(vNormal + bumpStrength * (noiseVal - 0.5) * vec3(1.0));
     // diffuse component (Lambert) with bump
     float lambert = max(0.0, dot(normalize(bumpNormal), -lightDirection));
     vec3 diffuse = vColor.rgb * lambert;

shaders/simple.vert

@@ -5,11 +5,13 @@ layout(location = 1) in vec4 aColor;
 layout(location = 2) in vec3 aNormal;
 out vec4 vColor;
 out vec3 vNormal;
+out vec3 vPosition;
 layout(location = 0) uniform mat4 transform;
 layout(location = 1) uniform mat3 normalMatrix;
 
 void main() {
     gl_Position = transform * vec4(position, 1.0);
     vColor = aColor;
+    vPosition = position;
     vNormal = normalize(normalMatrix * aNormal);
 }