ADD: Normal mapping

src/scene/tangent_space.h

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <vector>
+#include <cstddef>
+#include <core/vk_types.h>
+
+namespace geom {
+
+// Generate per-vertex tangents with a robust fallback when MikkTSpace is not available.
+// - Fills Vertex.tangent (xyz = tangent, w = handedness sign for B = sign * cross(N, T))
+// - Expects valid normals and UVs; if UVs are degenerate, builds an arbitrary orthonormal basis.
+void generate_tangents(std::vector<Vertex>& vertices, const std::vector<uint32_t>& indices);
+
+// Range variant for submeshes (indices [indexStart, indexStart+indexCount), vertices [vertexStart, vertexStart+vertexCount))
+void generate_tangents_range(std::vector<Vertex>& vertices, const std::vector<uint32_t>& indices,
+                             size_t indexStart, size_t indexCount,
+                             size_t vertexStart, size_t vertexCount);
+
+} // namespace geom
+