Not sure if I understand you right, but maybe this can help, though:
This is the main loop in doHybrid():
repeat
Rold := Rout;
while bTmp <= 0 do
begin
Inc(n);
if n > EndTo then n := iRepeatFrom;
bTmp := nHybrid[n] and $7FFFFFFF;
if bTmp > 0 then PVar := fHPVar[n];
end;
fHybrid[n](x, y, z, w, PIteration3D);
Dec(bTmp);
if nHybrid[n] < 0 then Continue else
begin
Inc(ItResultI);
Rout := x * x + y * y + z * z;
if Rout < OTrap then OTrap := Rout;
end;
until (ItResultI >= maxIt) or (Rout > RStop);
fHybrid is an array holding the formulas and member of the TPIteration3D structure. So my basic idea was, to call fHybrid[N](x, y, z, w, PIteration3D); from fHybrid[0](x, y, z, w, PIteration3D) where you have to calculate N inside of fHybrid[0] (which is the new formula to create).
I see. I was going a different route. I wanted to know where in the stack the next formula up is so that I could directly change the data in the stack.
We have this list of stack variables from the link you provided:
J4: Double; //-56 4d extension FastMove(dJUx, It3Dex.J1, 168);
Rold: Double; //-48 used by m3d, equals Rout
RStopD: Double; //-40 used by m3d for sse2, not always a valid value in here, in IFS: absDEstop
x: Double; //-32 vector to iterate -120 in dIFS esi
y: Double; //-24
z: Double; //-16
w: Double; //-8
C1, C2, C3: Double; //0 input start values before 4d rotation, C4 is 0. Do Not Change!
J1, J2, J3: Double; //+24 julia start values or the pixelpos, these are the constants to add
PVar: Pointer; //+48 pointer to the user input values (decreasing offset, -8 is always val 0.5) + constants (incr. offset, 0 and above)
SmoothItD: Single; //+52
Rout: Double; //+56 the square of the current vector length, calced in m3d, in dIFS: rel DEout
ItResultI: Integer; //+64 integer iteration count, increased by loop function in m3d
maxIt: Integer; //+68
RStop: Single; //+72 for dIFS: bool for insiderendering -> DEcomb with usual bulb needs RStop!!
So if I wanted the x_pixel value, I'd go for ESI+18h (ESI+24d).
DC46 18 FADD QWORD PTR DS:[ESI+18]
I was thinking that maybe there was a place to FSTP the formula number to ....
DD5D F8 FSTP QWORD PTR SS:[EBP-8]