feat: add click to select

destrum/assets_src/shaders/mesh.frag

@@ -13,9 +13,23 @@ layout (location = 1) in vec2 inUV;
 layout (location = 2) in vec3 inNormal;
 layout (location = 3) in vec4 inTangent;
 layout (location = 4) flat in uint inMaterialID;
+layout (location = 5) flat in uint inObjectID;
 
 layout (location = 0) out vec4 outFragColor;
 
+// Stable per object, the same object keeps its color between frames and runs
+vec3 selectionColor(uint objectID)
+{
+    if (objectID == 0u) {
+        return vec3(0.0);
+    }
+    uint hash = objectID * 2654435761u;
+    hash ^= hash >> 15;
+    hash *= 2246822519u;
+    hash ^= hash >> 13;
+    return vec3(hash & 255u, (hash >> 8) & 255u, (hash >> 16) & 255u) / 255.0;
+}
+
 vec3 calculateNormal(MaterialData material, uint samplerID)
 {
     vec3 n = normalize(inNormal);
@@ -127,6 +141,10 @@ void main()
         fragColor = mix(fragColor, lightHeatmapColor(tileLightCount), 0.5);
     }
 
+    if (pcs.sceneData.debugSelectionView != 0) {
+        fragColor = selectionColor(inObjectID);
+    }
+
     #if 0
     // TANGENT DEBUG
     if (inTangent == vec4(0.0)) {