A system tracks a user's hands by processing image data captured using one or more passive cameras. The system includes one or more passive cameras, such as color or monochrome cameras, and a hand tracking unit. The hand tracking unit receives the image data of the user's hand from the one or more passive cameras. The hand tracking unit determines, based on applying the image data to a neural network model, heat maps indicating locations of hand features of a hand shape model. The hand tracking unit may include circuitry that implements the neural network model. The neural network model is trained using image data from passive cameras, depth cameras, or both. The hand tracking unit determines a hand pose of the user's hand based on the locations of the hand features of the hand shape model. The hand pose may be used as a user input, or to render the hand for a display, such as in a head-mounted display.