Not sure if it is what you are looking for - I have used a very very basic software called "BMP 2 CNC" - it takes an image file (not just .bmp) and converts it to a "heightfield" using the grayscale of the image, then creates a toolpath directly in the software, no need to send to seperate CAM software. For example, black can be set to the concave areas and white can be the high areas (or vice versa), then any shade of gray between black and white will be a height proportionally between the low and high based on how dark or light it is. For clarity, I will attach a picture I just took of my first example of a logo that was machined into a block of plastic using this software (posted to a haas machine, using a .0625" ball end mill, then sandblasted). I will also include a small example of the image file used to get these results. As you can see in this example I set the dark as the "high" and light as the "low". The elliptical shape surrounding the text has a gradient from dark on the left to light on the right which is translated into a smooth ramp from the light to dark areas. The details are also picked up, like the little horizontal lines that run through the large text and also how the main text is slightly darker than the elliptical surrounding shape making the text appear to sit on top of it. Keep in mind it is very basic software. It is also very cheap (I think $20-30 to purchase the full, unrestricted version) so not much is to be expected. Some images will have better results than others. Sharply defined edges are a big plus. Hope this helps.