Perspective projection makes objects appear smaller as they move farther from the camera, creating familiar depth cues in a flat image.
Why equal objects look unequal
Two identical sculptures can occupy very different amounts of screen space if one is close to the camera and the other is far away. Their dimensions in the scene have not changed. Perspective describes how the camera projects them onto the image. It also makes parallel lines receding into depth appear to converge.
Camera movement is not object scaling
Moving the camera closer can enlarge an object on screen without changing its real size. Changing field of view alters the framing too. These controls can produce similar-looking screenshots but different spatial relationships. For example, a wide view taken close to a face can exaggerate the apparent difference between near and far features.
Reading an AR composition
If the back of an object looks smaller than its front in a Painta preview, check the viewing angle before correcting the model. Use a known dimension or a suitable orthographic view in the authoring tool when judging proportions. The animation compares the same depth movement under perspective and orthographic projection: only the perspective example changes apparent size.