feat: basic shadow map + renderdoc labels

destrum/assets_src/shaders/mesh.frag

@@ -6,6 +6,7 @@
 #include "scene_data.glsl"
 #include "mesh_pcs.glsl"
 #include "lighting.glsl"
+#include "shadows.glsl"
 
 layout (location = 0) in vec3 inPos;
 layout (location = 1) in vec2 inUV;
@@ -69,8 +70,17 @@ void main()
         uint lightIndex = pcs.sceneData.tileLightIndices.data[tileOffset + 1 + i];
         Light light = pcs.sceneData.lights.data[lightIndex];
 
+        float occlusion = 1.0;
+        if (light.castShadows != 0) {
+            occlusion = calculateDirectionalShadow(
+                fragPos, n,
+                pcs.sceneData.lightViewProj,
+                pcs.sceneData.shadowMapId,
+                pcs.sceneData.shadowNormalOffset);
+        }
+
         fragColor += calculateLight(light, fragPos, n, v,
-            diffuseColor, roughness, metallic, f0);
+            diffuseColor, roughness, metallic, f0, occlusion);
     }
 
     // emissive