diff --git a/README.md b/README.md
index 613b1ff..6acbaca 100644
--- a/README.md
+++ b/README.md
@@ -52,3 +52,23 @@ Examples of various shapes defined by SDF:
 ![ ](shapes.png)
 
 ![ ](m.png)
+
+# Reflection
+
+Source code: [reflection.c](reflection.c)
+
+Test scene with two boxes:
+
+![ ](reflection_boxscene.png)
+
+Visualization of SDF gradient, which is approximated by central difference:
+
+![ ](reflection_boxgradient.png)
+
+Reflection via recursive tracing:
+
+![ ](reflection_box.png)
+
+Concave mirror scene generates caustics effect:
+
+![ ](reflection_concavemirror.png)
diff --git a/makefile b/makefile
index 7a7677e..3d6cedb 100644
--- a/makefile
+++ b/makefile
@@ -1,4 +1,4 @@
-TARGETS=basic csg shapes
+TARGETS=basic csg shapes reflection
 OUTPUTS=$(addsuffix .png, $(TARGETS))
 TEXFILES=$(basename $(wildcard *.tex))
 DIAGRAMS=$(addsuffix .png, $(TEXFILES))
@@ -15,7 +15,7 @@ diagram: $(DIAGRAMS)
 
 %.png: %.tex
 	xelatex $<
-	convert $(basename $<).pdf $(basename $<).png
+	convert -density 150 $(basename $<).pdf $(basename $<).png
 	rm $(basename $<).aux $(basename $<).log $(basename $<).pdf
 
 clean:
diff --git a/reflection_box.png b/reflection_box.png
new file mode 100644
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diff --git a/reflection_boxgradient.png b/reflection_boxgradient.png
new file mode 100644
index 0000000..44c5b1d
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diff --git a/reflection_boxscene.png b/reflection_boxscene.png
new file mode 100644
index 0000000..7779221
Binary files /dev/null and b/reflection_boxscene.png differ
diff --git a/reflection_concavemirror.png b/reflection_concavemirror.png
new file mode 100644
index 0000000..284398f
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diff --git a/vector_reflect.png b/vector_reflect.png
new file mode 100644
index 0000000..11fa205
Binary files /dev/null and b/vector_reflect.png differ
diff --git a/vector_reflect.tex b/vector_reflect.tex
new file mode 100644
index 0000000..01a4027
--- /dev/null
+++ b/vector_reflect.tex
@@ -0,0 +1,20 @@
+\documentclass[tikz]{standalone}
+\usetikzlibrary{arrows,angles,quotes,calc,decorations.pathreplacing}
+\begin{document}
+\begin{tikzpicture}[>=triangle 45,line width=1.6pt,scale=1.5,font=\fontsize{20pt}{0},
+    interface/.style={
+        postaction={draw,decorate,decoration={border,angle=-45,
+                    amplitude=0.3cm,segment length=2mm}}}]
+  \coordinate (O) at (0,0);
+  \coordinate (V) at (-3,2);
+  \coordinate (R) at (3,2);
+  \coordinate (N)  at (0, 1.5);
+  \draw[blue,line width=.5pt,interface](-4,0)--(4,0);
+  \draw[->] (O) -- (N) node[anchor=south] {$\hat{\mathbf{n}}$};
+  \draw[->] (V) -- (O) node[midway, anchor=north east] {$\mathbf{i}$};
+  \draw[->] (O) -- (R) node[midway, anchor=north west] {$\mathbf{r}$};
+  \draw[->, blue, style=dashed] (V) -- (-3, 0) node[midway, anchor=east] {$(\mathbf{i} \cdot \hat{\mathbf{n}})\hat{\mathbf{n}}$};
+  \draw[->, blue, style=dashed] (-3, 0) -- (-3, -2) node[midway, anchor=east] {$(\mathbf{i} \cdot \hat{\mathbf{n}})\hat{\mathbf{n}}$};
+  \draw[->, style=dashed] (-3, -2) -- (O) node[midway, anchor=north west] {$\mathbf{r}$};
+\end{tikzpicture}
+\end{document}