[2018-03-28] User i_has_it found out that the only thing to make it work with S3D is to adapt the layer change script like that:

;LAYER:[current_layer]

[2018-01-25] Thanks to user groenewaldd's hints in the comments i have adapted the script to work for slic3r and Cura.

This is practically a remix of https://www.thingiverse.com/thing:2614204.
The difference is that it has an overhang on the right side with a pointy cone on top of it. This is supposed to show how exact your printer prints (and cools) small pointy details.
You also can change the direction of where the highest and the lowest temperature will print: on top or on the bottom of the tower.

Usage example in Slic3r:

1. Generate the tower with openscad:

$ openscad tempTower.scad 

Set the following variables in the openscad window to your liking:

// temperature of the first lowest blockstart_temp = 220;// temperature of the last highest blockend_temp = 185;// change in temperature between successively printed blockstemp_step = 5;

Render and export the model to .stl and close openscad.

2. Generate gcode with Slic3r:

1. Open the .stl file in Slic3r.
2. Set layer height to 0.2mm. If not, multiply the skip and block parameters by (0.2mm/new_layer_height).
3. Add the following to:
   "Printer Settings" -> "Custom G-code" -> "Before layer change G-code":

   ;LAYER:[layer_num]

   This makes it possible for the 'setLayerTemperatur.py' script to recognize the single layers.

4. Set the initial temperature in the filament settings. The pedestal on which the temperature tower stands will be printed with this temperature.
5. Save the .gcode file of the model.

Attention: maybe you will have to disable the 'Enable variable layer height feature:' checkbox in the printer settings in order to avoid messing up the temperature distribution over the tower height!

3. Write temperature settings to gcode file with setLayerTemperatur.py:

1. On the commandline:

   $ ./setLayerTemperatur.py -husage: setLayerTemperatur.py [-h] -s STARTTEMP -e ENDTEMP -t TEMPSTEP -f GCODEFILESets the proper temperatures to the corresponding layers of a gcode fileexported from Slic3r. This allows the temperature tower to have differenttemperatures per block.optional arguments:  -h, --help            show this help message and exitrequired arguments:  -s STARTTEMP, --startTemp STARTTEMP                        Temperature of the first (lowest) block.  -e ENDTEMP, --endTemp ENDTEMP                        Temperature of the last (highest) block.  -t TEMPSTEP, --tempStep TEMPSTEP                        Temperature change between successively printed                        blocks.  -f GCODEFILE, --gcodeFile GCODEFILE                        The .gcode file to process.

   $ ./setLayerTemperatur.py -s 240 -e 215 -t 5 -f tempTower_PETG_Black.gcode startTemp: 240endTemp:   215tempStep:  5gcodeFile: "tempTower_PETG_Black.gcode"outFile: "OUT_tempTower_PETG_Black.gcode"step: -5-> M104 S240-> M104 S235-> M104 S230-> M104 S225-> M104 S220-> M104 S215

   By now the different temperatures should have been written to a new .gcode file that starts with "OUT_" and ends with the name of your old .gcode file. This file you can send to your printer and the tower should be printed out with the different temperature settings.