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ns in 
figures 5 (b) and (d), which was computed in a separate step, 
blends well into the surrounding regions that were projected 
from the left view. The pink region in the right central part of 
the image is not a separate object, as indicated by the depth 
map. Its edges were therefore correctly overpainted by the 
rendering algorithm. 
  
  
(c) ground truth disparities — (d) strokes related to occlusions 
Figure 4. Disparity maps, occlusion map, and strokes emanating 
from the occluded regions for the Sawrooth set from figure 2. 
Similar results were obtained from tests with other stereo pairs, 
as shown in figures 6 through 9. In figures 6 and 7, the top row 
gives the original stereo video frames (size 640 x 480 pixels) 
that we captured in our lab. The corresponding disparity maps 
produced by stereo matching can be seen in subfigure (c). The 
occluded regions are marked in subfigure (d). For these two 
data sets, the occluded regions are larger than in the previous 
Sawtooth example. Nevertheless, no obvious artifacts are 
visible along the occlusion boundaries in the final results (see 
figures 8 and 9), which demonstrates the usefulness of the 
proposed approach. 
We displayed the painted images stereoscopically on both 
conventional computer monitors and a large Baron BARCO 
stereo table (Barco, 2004), and viewed them using active shutter 
glasses. The images were presented to several users. While 
most of the users were not aware of stereoscopic painting, they 
found the resulting paintings appealing and reported a better 
immersion into the artwork due to the new sense of depth. We 
varied the brush parameters to produce images with finer and 
coarser strokes, the latter making the painterly effect more 
noticeable. We found that the users tended to prefer coarser 
brush strokes on the stereoscopic presentation than when 
viewing the same image monoscopically. More tests would be 
required to examine whether this effect can be related to a 
reduced sensitivity of the eye due to stereoscopic fusion. 
For comparison, we also showed the stereo views that were 
generated individually using Hertzmann's original algorithm 
(see figure 3). Several of the test persons reported difficulties in 
fusing the non-coherent strokes, especially on coarser paintings. 
As regards computation time, our algorithm avoids re- 
calculating the strokes for large parts of the second image and 
thus achieves a speed-up over the straightforward creation of 
International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences, Vol XXXV, Part B3. Istanbul 2004 
two separate paintings, which becomes more significant as the 
image size increases. For an image of size 1600 x 1200 pixels, 
we measured a performance improvement of 13 96. 
4. SUMMARY AND OUTLOOK 
We have proposed a method for rendering artistic views of 
stereo images from real scenes. The stereo paintings produced 
by our algorithm give the impression of a painted world, in 
which the brush strokes are attached to objects. 
As the next step, we plan to render stereo views in different 
painting styles and present them to a larger group of test 
persons, in order to learn more about the special requirements 
of stereoscopic painterly rendering. Furthermore, we wvill 
investigate the effect of lower-quality disparity maps on the 
painting result. 
Our current implementation processes stereo videos on a frame- 
by-frame basis. For stereoscopic painterly animation, we plan to 
extend the algorithm using feature tracking in order to preserve 
both spatial and temporal coherence between brush strokes in 
consecutive stereo video frames. 
ACKNOWLEDGEMENTS 
This study has been supported by the Austrian Science Fund 
(FWF) under project P15663. We wish to thank 
“Verwertungsgesellschaft Bildender Künstler (VBK)", Austria, 
for permission to reproduce “The sleeping smoker”. 
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