1. A method comprising: receiving a first optical image of a 3-D printed object, the first optical image associated with a first optical imaging device perspective; and identifying a 3-D printing defect based on a first comparison between the first optical image of the 3-D printed object and an ideal object image, the ideal object image generated based on a 3-D object model and based on the first optical imaging device perspective, the first comparison including: generating a difference image based on a pixel-by-pixel comparison between the first optical image and the ideal object image; and generating a brightness image based on a pixel-by-pixel application of a brightness scaling factor to the difference image.