Here's a transparent heart, built on top of the 3D equation Dan found. Running the script is way more satisfying than the picture.
Surface Plot(
Show formula( 1 ),
Mode( "Isosurface" ),
Resolution( 101 ),
Surface Color( "Red" ),
Equation( "(x^2+9*y^2/4+z^2-1)^3-x^2*z^3-9*y^2*z^3/80" ),
SetVariableAxis( x, Axis Data( {Min( -1.3 ), Max( 1.3 ), Inc( 0.5 ), Minor Ticks( 1 )} ) ),
SetVariableAxis( y, Axis Data( {Min( -2 ), Max( 3 ), Inc( 1 ), Minor Ticks( 1 )} ) ),
SetVariableAxis( z, Axis Data( {Min( -1.3 ), Max( 1.3 ), Inc( 0.5 ), Minor Ticks( 1 )} ) ),
SetXVariable( x ),
SetYVariable( y ),
Frame3D( Set Graph Size( 700, 700 ), Set Spin( 0.004, 0, -0.5, -0.3 ), Set Rotation( -90, -10, 45 ) ),
);
3D heart
The surface plot takes the equation in X,Y,Z and shows the semi-transparent iso-surface.
Craige