Cfrgtkky

I have this 3D plot:

I would like to plot the function only over the region over the darker half of the bottom (the part closer to us).

Here is a MWE:

PassOptionsToPackage{usenames,dvipsnames,table,x11names}{xcolor}

documentclass[a4paper, 12pt]{article}

usepackage{pgfplots}

usepgfplotslibrary{colormaps,fillbetween}



begin{document}



begin{tikzpicture}



begin{axis}[

zmax=15,

zmin=0,

view = {45}{45},

grid=minor,

colormap={mycol}{color=(Tan), color=(Tan)},

xlabel = $s$,

ylabel = $h$,

zlabel = {$f(s,h)$},

ticks = none,

]



addplot3[

surf,

samples=30,

domain=0:1.5,

%y domain = 0:x, %does not work

opacity=0.5,

]

{12*exp(-(4*x+3*y))};



%highlighting dark part of bottom

filldraw[Tan, fill = Tan, opacity = 0, fill opacity = 0.5] (0,0,0) -- (1.5,1.5,0) -- (1.5,0,0) -- (0,0,0);



%line across bottom

draw[RawSienna, thick, opacity = 0.75] (0,0,0) -- (1.5,1.5,0);



%line going across graph

addplot3 [domain=0:1.5, RawSienna, thick, samples=30, samples y=0, opacity = 0.75] (x,x,{12*exp(-(7*x))});



end{axis}

end{tikzpicture}



end{document}

I tried to use y domain = 0:x, but that does not even compile (it takes too long and then craps out). Any suggestions?

Something like this? (Note that if you want a very old version instead of pgfplotsset{compat=1.16} this will have to be slightly modified, i.e. the coordinates in clip need to be prepended with axis cs:,
clip plot[variable=x,domain=0:1.5] (axis cs:x,x,{f(x,x)})
-- (axis cs:1.5,0,{f(1.5,1.5)}) -- (axis cs:0,0,{f(1.5,1.5)}) -- (axis cs:0,0,{f(0,0)});. )

PassOptionsToPackage{usenames,dvipsnames,table,x11names}{xcolor}

documentclass[a4paper, 12pt]{article}

usepackage{pgfplots}

pgfplotsset{compat=1.16}

usepgfplotslibrary{colormaps,fillbetween}



begin{document}



begin{tikzpicture}[declare function={f(x,y)=12*exp(-(4*x+3*y));}]



begin{axis}[

zmax=15,

zmin=0,

view = {45}{45},

grid=minor,

colormap={mycol}{color=(Tan), color=(Tan)},

xlabel = $s$,

ylabel = $h$,

zlabel = {$f(s,h)$},

ticks = none,

]



begin{scope}

 clip plot[variable=x,domain=0:1.5] (x,x,{f(x,x)})

 -- (1.5,0,{f(1.5,1.5)}) -- (0,0,{f(1.5,1.5)}) -- (0,0,{f(0,0)});

 addplot3[

 surf,

 samples=30,

 domain=0:1.5,

 %y domain = 0:x, %does not work

 opacity=0.5,

 ] {f(x,y)};

end{scope}



%highlighting dark part of bottom

filldraw[Tan, fill = Tan, opacity = 0, fill opacity = 0.5] (0,0,0) -- (1.5,1.5,0) -- (1.5,0,0) -- (0,0,0);





%line across bottom

draw[RawSienna, thick, opacity = 0.75] (0,0,0) -- (1.5,1.5,0);



line going across graph

addplot3 [domain=0:1.5, RawSienna, thick, samples=30, samples y=0, opacity = 0.75] 

(x,x,{f(x,x)});



end{axis}

end{tikzpicture}



end{document}