An example apparatus has a processor to analyze images of projected shifted versions of a fringe pattern onto a scene to obtain phase information associated with the pixels in the image. Topology information is derived by correcting the phase information using a phase offset associated with a combination of two subsequent versions of the fringe pattern in the images or by estimating a surface normal for each pixel using a partial derivative of the phase information of the pixel in a first spatial direction and a partial derivative of the phase information of the pixel in a second spatial direction.