You can use the Multi-Ring Buffer tool that will create a polygon layer with three attributes:
OBJECTID: The original ID of the point
RingId: a sequence of numbers from 1 to the amount of buffers you perform in each point.
distance: the distance from the original point to the buffer.
Running this tool from 2 points, 5 buffers and a spacing of 5 meters will ...
You can achieve this in two steps.
First you need to create a raster with the distance to your line using the tool Euclidean Distance. This will create a raster from 0 to 20 (if you limit the distance to 20m).
And from here you can operate this raster using the Raster Calculator that in your case would be dividing your raster by 20.
Run the regular buffer tool twice and use the data in the attribute table as the buffer distance parameter. After running buffer twice you will have a pre and a post growth buffer layer. If you want the two buffer outputs in the same feature class use append or merge to combine them.
You can try using a virtual layer.
Go to the menu Layer > Add Layer > Add/Edit Virtual Layer... and enter the following query. Feel free to add any field of interest from the layer.
select st_buffer(geometry,raio_metade) as geometry, raio_metade
I'm using QGIS 3.10 but I believe this works for 3.4 as well. Zoom until you have the buffer area in your view then go to Project>Import/Export>Export Map to Image. In the resulting dialog click on Map Canvas Extent to set the extent of your export to what you see on the screen. Also make sure that the Append Georeference Information is checked this will ...