added sphere sphere solution

pstricks/sphere-sphere/Makefile

@@ -0,0 +1,37 @@
+SOURCE = sphere-sphere
+DELAY = 80
+DENSITY = 300
+WIDTH = 512
+
+make:
+	latex $(SOURCE).tex -output-format=pdf
+	dvips -D600 $(SOURCE).dvi -o $(SOURCE).ps
+	ps2pdf $(SOURCE).ps $(SOURCE).pdf
+	make clean
+
+clean:
+	rm -rf  $(TARGET) *.class *.html *.log *.aux *.data *.gnuplot *.dvi *.ps
+
+gif:
+	pdfcrop $(SOURCE).pdf
+	convert -verbose -delay $(DELAY) -loop 0 -density $(DENSITY) $(SOURCE)-crop.pdf $(SOURCE).gif
+	make clean
+
+png:
+	make
+	make svg
+	inkscape $(SOURCE).svg -w $(WIDTH) --export-png=$(SOURCE).png
+
+transparentGif:
+	convert $(SOURCE).pdf -transparent white result.gif
+	make clean
+
+svg:
+	make
+	#inkscape $(SOURCE).pdf --export-plain-svg=$(SOURCE).svg
+	pdf2svg $(SOURCE).pdf $(SOURCE).svg
+	# Necessary, as pdf2svg does not always create valid svgs:
+	inkscape $(SOURCE).svg --export-plain-svg=$(SOURCE).svg
+	rsvg-convert -a -w $(WIDTH) -f svg $(SOURCE).svg -o $(SOURCE)2.svg
+	inkscape $(SOURCE)2.svg --export-plain-svg=$(SOURCE).svg
+	rm $(SOURCE)2.svg

pstricks/sphere-sphere/Readme.md

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+This is an example from `pst-solides3d` documentation.
+
+Compiled example
+----------------
+![Example](sphere-sphere.png)
+
+Credits
+-------
+Thanks to [Herbert](http://tex.stackexchange.com/users/2478/herbert) ([answer](http://tex.stackexchange.com/a/121906/5645))

pstricks/sphere-sphere/sphere-sphere.tex

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+\documentclass[pstricks,border=2pt]{standalone}
+\usepackage{pst-solides3d}
+\begin{document}
+
+\begin{pspicture}(-4.5,-4)(5.5,2)
+\psset{solidmemory,unit=0.55,
+       lightsrc=viewpoint,viewpoint=20 20 20 rtp2xyz,Decran=40}
+\psSolid[object=sphere,r=2,ngrid=36 36,fillcolor=lightgray,
+    incolor=lightgray,hollow,name=sph1,action=none](3,0,0)
+\psSolid[object=sphere,r=2,ngrid=36 36,fillcolor=lightgray,
+    incolor=lightgray,hollow,name=sph2,action=none](1,3,0)
+\psSolid[object=fusion,base=sph1 sph2,opacity=0.5,action=draw**](0,0,0)
+\end{pspicture}
+
+\end{document}