but I suppose it depends on the look you're shooting for. Of course, you can't simply make a mold from a photo, since a photo is flat. So you have to decide what it is about the photo that you want to translate into the third dimension. If the photo is highly linear, then you can trace each line in a computer program, and then use those traces to guide your laser (or an endmill in a CNC mill). If it's more a series of gray-scale gradations, then you either have to arbitrarily decide where to place your lines to bring out the shapes you're interested in, or use a different process called a "heightfield" to create a relief where the lightest pixels are the highest, and the darkest ones the lowest points of a mesh. This can then be used in a CNC mill, which can carve it out. Of course, this process will generate certain artifacts which might detract from its realistic appearance, but that goes with the territory.
If you are planning to press clay into these molds, then plaster is a better material than aluminum, which tends to stick to clay. It's easy enough to carve your relief as a positive in machinable wax, and to make a plaster mold from that, although some people have had success in carving plaster directly.
If I were you, I'd start with some inexpensive software that can do the modeling or drawing part of this, and see how I liked the results before investing in expensive production equipment. There are plenty of people here in the Zone who can do a test carving or laser cut for you, once you have a model you're happy with.
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