Updated: Jul 15, 2020
When you start printing bigger and bigger objects you will notice you will need to increase the display time so that part of the object will form while another part of the object already formed. This is because of the hotspot. The location on the build plate that is closest to the lamp on the projector is also the location on the build plate that gets the most power. As you go to the edges the power reduces. With the Acer projector the top left corner seems to be the weakest point.
First step with hotspot compensation is to load a hotspot tester STL. In the Gizmo3DPrinters\toolbox\calibrate directory you will find HotspotTest 200mm x 113mm Columns.STL and also the Solidworks part file. This fill will create a base and then a thin pillar. Load this file into Gizmetor and slice it. This file is for when you have a projection area that is 200mm wide.
After slicing, open GiziPrint. Go to the tools tab and click on "Import Hotspot compensation". Select the file Gizmo3DPrinters\toolbox\calibrate\Hotspot calibration.csv. This file already contains starting values.
If you open the file in Excel, don't use Word or Wordpad, you will notice values ranging from 0 to 0.73 or maybe even higher. These values will be used to create a grid pattern of light and dark blocks. 0 means the block is completely see-through. 1 means the block is completely black. You normally don't want to go over 0.8 and you would normally have the edges at 0 since that is where the least amount of power is.
So now that you have loaded the hotspot compensation file you need to test the compensation.
In GiziPrint just follow through the screens up to the last screen. Change the display time to 1000ms and print. If any of the pillars formed when the print is done then edit the CSV file. Increase the values for those columns by 0.1, import the file again and print again at 1000ms. If nothing formed then print at 2000ms and do the same over and over until you have all the pillar form.
Please note: Hotspot compensation will slow down the printing. The compensation reduces the power overall. You will get better printing results, because you will have a more uniform power outpot over the build plate. You can remove hotspot compensation by importing "Hotspot None.csv". In the future hotspot compensation will always be enabled to allow us to move closer to "1 click printing" and you will have to disable it in overrides.