Plot3D[1,{x,0,1}, {y,0,1}]

p:=Polygon[{{0,0.35},{0.75,0.2}, {0.85,0.65}, {0.3,0.9}, {0,0.65}}]

Plot3D[1,{x,y} ∈ p, ViewPoint->{0,0,∞}]

Plot3D[1,{x,y} ∈ p]

sigma=0.5/Sqrt[-2*Log[0.025]]

Plot3D[Exp[-((x-0.5)^2+(y-0.5)^2)/(2*sigma^2)],{x,0,1}, {y,0,1}]

Plot3D[Exp[-((x-0.5)^2+(y-0.5)^2)/(2*sigma^2)],{x,y} ∈ p]

k4=4*(0.5/(-4*Log[0.025])^(1/4))^4

Plot3D[Exp[-(Sqrt[(x-0.5)^2+(y-0.5)^2]^4)/k4],{x,0,1}, {y,0,1}]

Plot3D[Exp[-(Sqrt[(x-0.5)^2+(y-0.5)^2]^4)/k4],{x,y} ∈ p]

k25=2.5*(0.5/(-2.5*Log[0.025])^(1/2.5))^2.5

Plot3D[Exp[-(Sqrt[(x-0.5)^2+(y-0.5)^2]^2.5)/k25],{x,0,1}, {y,0,1}]

Plot3D[Exp[-(Sqrt[(x-0.5)^2+(y-0.5)^2]^2.5)/k25],{x,y} ∈ p]