After opening the design you wish to change in GCS, select the RENDER button and leads you to a screen that allows you to select a different material that you cut in the same design. Now return to the main screen and select Tools then manual optimizer. You now see what the original design looks like in the new material. If you don’t like it, you can now use the Manual Optimizer to change it to suit you. GCS will change the angles for the whole stone depending on the changes that you make. Now you have a design that looks the same but gives the performance you want in the new material. You often don’t really need to change the angles for a different RI if the RI is greater than the original gemstone’s value.