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

src/dev_panel.cpp

@@ -657,6 +657,16 @@ void DevPanel::show_shader_tab_item() {
         ImGui::SliderFloat("Cloud Threshold High",
                            &m_app.renderer().cloud_threshold_high(), 0.0f,
                            1.0f);
+        ImGui::SliderFloat("Water Refract Strength",
+                           &m_app.renderer().refract_strength(), 0.0f, 1.0f);
+        ImGui::Checkbox("Water Perturb", &m_app.renderer().water_perturb());
+        ImGui::SameLine();
+        ImGui::Checkbox("WaterDepthFade", &m_app.renderer().water_depth_fade());
+        ImGui::SliderFloat("Underwater Fog Density",
+                           &m_app.renderer().underwater_fog_density(), 0.0f,
+                           1.0f);
+        ImGui::SliderFloat("Water Density", &m_app.renderer().water_density(),
+                           0.0f, 1.0f);
         ImGui::EndTabItem();
     }
 }