MC image rendering

[madaussie]

Hi from Australia,  I'm hoping someone can offer a reason for a slow render of both normal and MC images.  I'm using a multi core i7 computer which normally renders images quite fast but not the following mandelbulb 3d:
Mandelbulb3Dv18{
g....UL/..U42...ET...2Q...EGmLLgxbA1.dnSwukbI31EabYN71.ogzvKd3BKiN1zzQ8/e.ofkp.E
................................5/ZMG3SZ6/2........Y./.........E........y.2...wD
...Uz6/....d..../M.1/.....kzK...F4....EC.....cGyQZ/g//kD/.k4v8DEgQPs.dkpXm1.....
./EnAnQD1A../2.........../................................U0.....y1...sD...../..
.w1...sDMk4b..LE.wX0pcoCv.RYy2FuiVum8mcDxlru/2eUKu1jlnHfWA4zy0RhwqVzlyijw2st9v0C
itnJXDfIx8vvygXMiE/SXljjU.....Yb4/............kD.2....sD/.G.....................
.............oAnAt1...sD....zw1...................................k4v8DEe.....x/
.....Ksulz1.....szzz.wzzz1.U..6.5....w0...EB....v0....8....9....l....oHB...UibTZ
ht4U.0aZczDM6/nz....z1......0c..zrhe..klrlkCx9yj6Eot8VlJ4z1...........U.8..Xo/2.
..........6.fjrwdvgez0........../AV0.6oIr/...........u/...................E.lc..
uUXA..EWD7yHGpzD.0..........meZpwzPpzKE28cTAoY3..k6asV91yz18ZYMMuA6cz.UfeWQbzovj
32V0v9XBM/..IhqEOnUzz..NOMEh20uD.6MxWxXaxy9..I5VG1....kCLe.V414.NgV4sUK3Yi8m.2gd
Xu7kUoiYQ0Ejzu9Vkdmo2z5.7BoK.AlBTLsZ.....gXUz6urJ1.W2Ks4cxpsH95.IQ/3S4bPwKth....
.ElAzRRoY0.....3...y3q/bzz/k.1Akyz1yATomxzpaqaff.k4Qc3qEZt4GZ7HAl2nLgxaQZtaSd71A
E../.EkAF3.6....2....A....EEh3aSdtqNU6oPs/UQ..........................k/9.......
...................wz...........BnAnAnAngz1.....................................
................................................................................
.....................2.....3....6....wJNTB1FoJqQn/EM.AJFm..............y3q/.sLM5
........06....................................................zD........kz1.....
...wz.....................2..z5y3q/.sLM5....sLM5.wz5.1Ak.szDsnwF.ozLPOPi........
........................../...k./....E/...U0....BJaPbJaQn.ERg34.ExqR............
................4MU/4MU/................6.2........wz.........zD........kz1.....
................tpEtpEtph.2.....................................................
..........................................E.....I....Q....EHVRaJnVJKO3aMn71..E4.
.....................................................d2qGooyVYzD8Vh2BhT6tz1.....
..............zD........kz1........wz.........................................yD
........Uz9.............................................}
{Titel: 231212-3}
Any help appreciated as the first pass in MC looks like taking in excess of 17 hours.  Heaven knows how long for the next pass.  I usually allow for 54 or more rays.  ie at least 3 passes.
Madaussie

[bib]

Try to increase DE Stop to 0.5 or 1 and see if that doesn't kill too much the details. 0.1 is generally too expensive in calc time, except when you really need to get rid of noisy artifacts.

Also, set a lower max number of iterations. 2000 iterations is useful only when you zoom. You could work with 40-50 iterations without any noticeable difference.

Hope this helps!

[madaussie]

Thanks for the info.  I'm unsure how to set the iterations as this is the first time I've seen reference to this.  Please explain.
madaussie

[bib]

Thanks for the info.  I'm unsure how to set the iterations as this is the first time I've seen reference to this.  Please explain.
madaussie

At the bottom of the Formulas window there is a "Max. Iteration" field.

[Madman]

You're also using a couple of formula's that have a serious impact on rendering time. Do you really need Formula 4? If you throw it away, you'll reduce rendering speed at a factor 6. Throw away Formula 2 and you'll reduce the rendering time with another factor 4. I know, it has a huge impact on the artistic result, but if the possibilities are infinite, you might want to skip the slow formula's...

[madaussie]

bib, reduced the iterations and found very little difference in time on a laptop ( both about 60 minutes to render image on laptop).  Not the MC version.  One big difference was the absence of colour in the 60 iteration render.  Can't explain why this should be so.

madman, tried you suggestion.  Rendering certainly reduced to about 5 minutes, but image not what I'm aiming for.  Currently halfway into second MC pass.  Looks like this pass will take 2 days!  Guess I will have to put up with the long render time for this mandelbulb.

madaussie

[lenord]

MonteCarlo rendering is notoriously slow to begin with although the results are startlingly Good. Otherwise the biggest drag on Render time of the normal raytrace on this is the MagVsXYZabs2 Formula, it's a time killer and the _e_3Dtess ain't a lot better either, there are other Formulas too that alone or combined with others I just won't use because I just don't have the patience.