feat: water effects (#19)

* feat(shaders): add lighting to block accumulation OIT shaders

* feat(renderer): add water rendering with OIT and new shaders

* feat(water): implement screen-space reflection and refraction for water with depth fade and perturbation

* refactor(shader): replace glUniform calls with generic set_loc and remove cached locations

* feat(water): add noise-based caustics and configurable fog density

* fix(water shader): update depth fade and remove underwater check

- Increase DEPTH_FADE_DISTANCE from 8 to 10
- Remove conditional so depth fade always applies
- Darken deepColor from (0, 0.08, 0.15) to (0, 0.015, 0.045)

* feat(underwater): add volume scattering and shadow mapping for light shafts

assets/shaders/block_accumulation_f_shader.glsl

@@ -4,10 +4,21 @@ layout (location = 0) out vec4 accum;
 layout (location = 1) out float reveal;
 
 in vec2 tc;
+in vec3 normal;
+in vec3 vert_pos;
+in float roughness;
 flat in int tex_layer;
 in float v_depth;
 layout (binding = 0) uniform sampler2DArray samp;
 
+uniform float ambientStrength;
+uniform vec3 sunlightColor;
+uniform vec3 ambientColor;
+uniform vec3 sunlightDir;
+uniform vec3 cameraPos;
+uniform bool shader_on;
+uniform float specularStrength;
+
 float weight(float z, float a) {
     float intermediate = 0.03 / (1e-5 + pow(z / 200.0, 4.0));
     
@@ -15,7 +26,71 @@ float weight(float z, float a) {
 }
 
 void main() {
-    vec4 color = texture(samp, vec3(tc, tex_layer));
+
+    vec4 objectColor = texture(samp, vec3(tc, tex_layer));
+
+    if (!shader_on) {
+        vec4 color = objectColor;
+        float alpha = color.a;
+        if (alpha < 1e-4) discard;
+
+
+        float w = weight(v_depth, alpha);
+
+        accum = vec4(color.rgb * alpha * w, alpha * w);
+
+        reveal = alpha;
+        return;
+    }
+   
+    vec3 lightDir = normalize(-sunlightDir);
+    
+    vec3 norm = normalize(normal);
+
+    vec3 V =
+        normalize(cameraPos - vert_pos);
+
+    vec3 H = 
+        normalize(lightDir + V);
+
+    vec3 ambient = ambientStrength * ambientColor;
+    
+    float diff = max(dot(norm, lightDir), 0.0);
+    
+    vec3 diffuse = diff * sunlightColor;
+    
+    float r =
+        clamp(roughness, 0.0, 1.0);
+
+    float shininess =
+        mix(
+            512.0,
+            4.0,
+            r
+        );
+    float ks =
+        mix(
+            0.8,
+            0.02,
+            r
+        );
+
+    float spec = 0.0;
+
+    if(diff > 0.0)
+    {
+        spec =
+            ks *
+            pow(
+                max(dot(norm,H),0.0),
+                shininess
+            );
+    }
+    
+    vec3 specular = spec * sunlightColor * specularStrength;
+  
+    vec4 color = vec4((ambient + diffuse) * objectColor.rgb + specular, objectColor.a);
+
     float alpha = color.a;
     if (alpha < 1e-4) discard;