cylinder @ R @ x^2 + y^2 - R^2 = 0 @ Cylinder along z-axis, axis going through (0,0,0)
cylinder_dent @ R l a @ x^2 + y^2 - r(z)^2 = 0, r(x) = R if | z | > l, r(z) = R - a*(1 + cos(z/l))/2 otherwise @ A cylinder with a dent around z = 0
dumbbell @ a A B c @ -( x^2 + y^2 ) * (a^2 - z^2/c^2) * ( 1 + (A*sin(B*z^2))^4) = 0 @ A dumbbell @
dumbbell @ a A B c @ -( x^2 + y^2 ) + (a^2 - z^2/c^2) * ( 1 + (A*sin(B*z^2))^4) = 0 @ A dumbbell
ellipsoid @ a b c @ (x/a)^2 + (y/b)^2 + (z/c)^2 = 0 @ An ellipsoid
gaussian_bump @ A l rc1 rc2 @ if( x < rc1) -z + A * exp( -x^2 / (2 l^2) ); else if( x < rc2 ) -z + a + b*x + c*x^2 + d*x^3; else z @ A Gaussian bump at x = y = 0, smoothly tapered to a flat plane z = 0.
plane @ a b c x0 y0 z0 @ a*(x-x0) + b*(y-y0) + c*(z-z0) = 0 @ A plane with normal (a,b,c) going through point (x0,y0,z0)
plane_wiggle @ a w @ z - a*sin(w*x) = 0 @ A plane with a sinusoidal modulation on z along x.
sphere @ R @ x^2 + y^2 + z^2 - R^2 = 0 @ A sphere of radius R
supersphere @ R q @ | x |^q + | y |^q + | z |^q - R^q = 0 @ A supersphere of hyperradius R
spine @ a, A, B, B2, c @ -(x^2 + y^2)*(a^2 - z^2/f(z)^2)*(1 + (A*sin(g(z)*z^2))^4), f(z) = c if z > 0, 1 otherwise; g(z) = B if z > 0, B2 otherwise @ An approximation to a dendtritic spine
spine_two @ a, A, B, B2, c @ -(x^2 + y^2)*(a^2 - z^2/f(z)^2)*(1 + (A*sin(g(z)*z^2))^2), f(z) = c if z > 0, 1 otherwise; g(z) = B if z > 0, B2 otherwise @ Another approximation to a dendtritic spine
spine @ a, A, B, B2, c @ -(x^2 + y^2) + (a^2 - z^2/f(z)^2)*(1 + (A*sin(g(z)*z^2))^4), f(z) = c if z > 0, 1 otherwise; g(z) = B if z > 0, B2 otherwise @ An approximation to a dendtritic spine
spine_two @ a, A, B, B2, c @ -(x^2 + y^2) + (a^2 - z^2/f(z)^2)*(1 + (A*sin(g(z)*z^2))^2), f(z) = c if z > 0, 1 otherwise; g(z) = B if z > 0, B2 otherwise @ Another approximation to a dendtritic spine
thylakoid @ wB LB lB @ Various, see "(Paquay)"_#Paquay1 @ A model grana thylakoid consisting of two block-like compartments connected by a bridge of width wB, length LB and taper length lB
torus @ R r @ (R - sqrt( x^2 + y^2 ) )^2 + z^2 - r^2 @ A torus with large radius R and small radius r, centered on (0,0,0) :tb(s=@)
