From 2a3337a912569c6d961d002178cdbac7912e1ecc Mon Sep 17 00:00:00 2001
From: lisyarus <lisyarus@gmail.com>
Date: Sun, 13 Dec 2020 16:10:40 +0300
Subject: [PATCH] Implement bump-mapping in pcg

---
 libs/pcg/include/psemek/pcg/bump.hpp | 50 ++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)
 create mode 100644 libs/pcg/include/psemek/pcg/bump.hpp

diff --git a/libs/pcg/include/psemek/pcg/bump.hpp b/libs/pcg/include/psemek/pcg/bump.hpp
new file mode 100644
index 00000000..0b931c03
--- /dev/null
+++ b/libs/pcg/include/psemek/pcg/bump.hpp
@@ -0,0 +1,50 @@
+#pragma once
+
+#include <psemek/pcg/seamless.hpp>
+
+#include <psemek/gfx/pixmap.hpp>
+
+namespace psemek::pcg
+{
+
+	inline gfx::basic_pixmap<geom::vector<float, 3>> bump(gfx::pixmap_float const & height_map, seamless_tag)
+	{
+		gfx::basic_pixmap<geom::vector<float, 3>> result(height_map.dims());
+
+		float const dx = 1.f / result.width();
+		float const dy = 1.f / result.height();
+
+		for (auto i : result.indices())
+		{
+			auto ix0 = i;
+			ix0[0] = (ix0[0] + result.width() - 1) % result.width();
+
+			auto ix1 = i;
+			ix1[0] = (ix1[0] + 1) % result.width();
+
+			auto iy0 = i;
+			iy0[1] = (iy0[1] + result.height() - 1) % result.height();
+
+			auto iy1 = i;
+			iy1[1] = (iy1[1] + 1) % result.height();
+
+			float h = height_map(i);
+			float hx0 = height_map(ix0);
+			float hx1 = height_map(ix1);
+			float hy0 = height_map(iy0);
+			float hy1 = height_map(iy1);
+
+			auto n = geom::vector<float, 3>::zero();
+
+			n += geom::normalized(geom::vector{hx0 - h, 0.f, dx});
+			n += geom::normalized(geom::vector{h - hx1, 0.f, dx});
+			n += geom::normalized(geom::vector{0.f, hy0 - h, dy});
+			n += geom::normalized(geom::vector{0.f, h - hy1, dy});
+
+			result(i) = geom::normalized(n);
+		}
+
+		return result;
+	}
+
+}