Morphing and Warping

Morphing

2D Image Morphing

= the construction of an image sequence depicting a gradual transition between two images.

Geometric Transformations are used to create the image distortions known as Morphing and Warping.

Some algorithms do Feature-based Morphing.

This is where you associate features like lines and points in one image with other features in another image. The resulting mapping (transformations) are used in producing the sequence of in-between images.

2D Morph Movies

The Idea

Setup Correspondences between Source and Destination Images

Algorithm to compute new in-between image(s)

For each pixel X in destination

{      DSUM = 0;

weightsum = 0;

for each line (Pi, Qi)

{ calculate (u,v) based on (Pi,Qi)

  calculate (u', v') based on (Pi', Qi')

  weight = legthn/(a+distance)

  DSUM += weight* (X'-X)

  weightsum += weight        }

X' = X + DSUM/weightsum;

desitination[X] = source[X'];

}

3D Morphing

3D Morph Sequence

Stanford U. Research Paper with details of algorithm

from http://graphics.stanford.edu/cgi-bin/alumni/tolis/personal/getpage.cgi?morph.html

= generates intermediate 3D models, the morphs, directly from the given models; the morphs are then rendered to produce an image sequence depicting the transformation.

overcomes the following shortcomings of 2D morphing

Creating 3D morphs is independent of the viewing and lighting parameters.
In 2D morphing, a new morph must be recomputed every time we wish to alter our viewpoint or the illumination of the 3D model. 2D techniques, lacking information on the model's spatial configuration, are unable to correctly handle changes in illumination and visibility. Two examples of this type of artifact are: (i) Shadows and highlights fail to match shape changes occuring in the morph. (ii) When a feature of the 3D object is not visible in the original 2D image, this feature cannot be made to appear during the morph; for example, when the singing actor needs to open her mouth during the morph, pulling her lips apart thickens the lips instead of revealing her teeth.