How to fill a disk (based on percentage full) from the bottom up

Question

Is it possible to fill a Disk from the bottom up without plotting circles? The way I've been doing it by plotting circles is too complicated for such a simple outcome. I am trying to fill Disks like the ones in this picture

Answer 1

Are you looking for something like this?:

Manipulate[Graphics[{{Black, Thickness[0.01], Circle[{0.5, 0.5}, 0.5]}, {Cyan, 
DiskSegment[{0.5, 0.5}, 0.5, {(270 Degree - 180 Degree*a), (270 Degree + 180 Degree*a)}]}}, PlotRange -> {{0, 1.01}, {-0.01, 1}},
AspectRatio -> 1], {a, 0.01, 1., 1/180}]

Answer 2

Here's a short demo you can start with:

Manipulate[With[{t = segmentOffset[f]}, 
                Graphics[{{Directive[Red, Thick], Circle[]},
                          {LightBlue, DiskSegment[{0, 0}, 1, {π + t, 2 π - t}]}}, 
                         PlotLabel -> Row[{"% filled: ", 50 (π - 2 t - Sin[2 t])/π}], 
                         PlotRange -> 1]], {f, 0, 1, 1/20}, 
           Initialization :> (segmentOffset[f_?NumericQ] /; 0 <= f <= 1 :=
                              With[{y = π (1 - 2 f)}, \[FormalX]/2 /. 
                                   FindRoot[y == \[FormalX] + Sin[\[FormalX]],
                                            {\[FormalX],
                                             y (1 - 125 y^2/2352)/
                                             (2 + y^2 (47 y^2/47040 - 29/196))}]])]

Answer 3

I suggest the following minor graphics improvements to show the fill inside a thicker circular vessel:

Manipulate[
Graphics[{{Black, Thickness[0.02], Circle[{0.5, 0.5}, 0.512]},
{Cyan,DiskSegment[{0.5, 0.5}, 
0.5, {270 \[Degree] - 180 \[Degree] a, 
270 \[Degree] + 180 \[Degree] a}]}}, 
PlotLabel -> Row[{"% Filled :  ", 100 a}, Frame -> True], 
PlotRange -> {{-0.05, 1.05}, {-0.05, 1.05}}, AspectRatio -> 1, 
ImageSize -> 400], {a, 0.01, 1, 18/1800}, ImageMargins -> 10, 
FrameMargins -> Large]

Note the blue fill does not encroach on the vessel inner wall.