How to use MegaPack:
Start MegaPack, click the "Add list of BMP's..." button, now you can browse for the .lst file that you previously created which contains a list of all the .bmp frames you want to pack into the .GP file. The .lst file MUST be in the same folder as your .bmp frames. Open the .lst file, now you will see the "Conversion properties" window pop up. This is where you select what kind of packing options you would like use, this will affect the finished units/buildings quality, some of these options are essential for everything to run smooth in the game. In the "Image type and packing" drop down menu select "Simple packing image". From the "Packing quality" drop down menu there are a number of options that are specific to certain animations. For building animations or still frames select "Precise image[0]". For walking animations select "Standart quality[3]". For other animations such as death, attack, reload, shot etc. select "Good quality[1]".

Now for the "Scaling" drop down menu you need to find the right scaling option/size, you need to render your units with whatever 3D modeling program you use to a size that will match the units size in American Conquest, you can get the size right in your 3D modeling program and just do a "Normal size" scale. I normally render my units around 4 to 5 times larger, then I scale them 1/4 to 1/5 in size with MegaPack to get the right size for the game, this ensures a good quality unit.

In the "GP-file name" box you need to type the name you want the .GP file to be called. 

There are also some other options at the bottom which you don't really need to use, except "Anti-aliasing" which will make any jagged edges appear smooth. It is not recommended for death or walking animations. 

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Click to enlarge

Now click the "OK" button at the top of the "Conversion properties" window. At the bottom of the MegaPack window in the "Output directory" box browse to where you want to save the finished .GP file to. In the "Palette" check box, check "Palette 0" if the .GP is for American Conquest or "Palette 1" if the .GP is for Cossacks. In the MegaPack main window click on the selection that you want to process, then click the "Convert selected" button to start the packing process. When the packing process is finished you will find you completed .GP file in the folder you specified. You can also save your .GP projects if you click the "Save project" button.

Open the .GP file with the Graphics Packages Viewer tool to check the quality and size of the unit and also to check that the animation runs smoothly and appears normal at all angles.

Click to enlarge

Click to enlarge