Techniques and systems for 3D printing with machines having imperfect light projection are described. A technique includes receiving an intensity map comprising a plurality of pixel values, wherein the pixel values of the intensity map represent variations in intensity of light projection of an additive-manufacturing apparatus; receiving cross-sectional images of a three dimensional (3D) model of an object, each cross-sectional image comprising a plurality of pixel values, each pixel value of each cross-sectional image having an X-location and a Y-location; for each cross-sectional image of the 3D model, applying pixel values of the intensity map to corresponding pixel values of the cross-sectional image of the 3D model, to make one of a plurality of additive-manufacturing images that are calibrated to account for the variations in intensity of the light projection; and providing the additive-manufacturing images to the additive-manufacturing apparatus to build the object.