The second method of low poly I will describe is the more time-consuming one, but I think it yields the greatest results. The first step is to select an image. Once you have imported your picture into Illustrator, you will want to show the rulers if they are not already visible. To accomplish this, go to the View tab, then Rulers, and then Show Rulers.
Step 1:
Once you have your rulers shown, draw a guide line along the centre of the picture. This is because we only utilise half of the image and then reflect it to make it symmetrical.
Step 2:
You must now begin sketching your triangles. If you have a wide area, you may use larger triangles, but if you have a little area, you must use smaller triangles. You must first pick the pen tool, making sure that no fill is chosen but that it has a stroke on it so that you can see the edges, and then you can begin.
Step 3:
When colouring the picture, make sure that the colours do not shift too much unless absolutely necessary; for example, if it goes from black to white, consider adding a few of shades of grey in there to make it seem smoother.
Step 4:
When you are finished, you should remove the image but not your work. Then copy and paste it over the top of the original one, using Ctrl + F to paste anything on top of where you copied from. The last step is to reflect the picture.
Step 5:
After you have mirrored the duplicate, just drag it into place, and your geometric low poly image is complete.
Try this method if you want low poly reflection in Adobe Illustrator.