Figure 5.1: Problem of full overlap check.
pairs in an increasing order of the weight. By this simple algorithm, we can obtain a simplified line drawing.
5.2 Future Works
The combination process seems lack of some conditions, since we can not combine the strokes even if the strokes are very close to each other. Obviously, these phenomena are due to the check of full overlapping between two strokes. If we neglect this limit, some of the results will lose some strokes at strange place. But in the model “Gandhi”, combination can be done better as shown in Figure 5.1. We are still finding the lacking conditions.
Although we can simplify the strokes with the proposed simple algorithm, we have to use many user-defined parameters. The users need to try and error to get the best result. They need to know the meaning of each parameter. We also have not found the best simplification order.
Furthermore, we still can not simplify the strokes locally. Last, too many strokes will result in a very long computation time.
In the future, we need to solve the above three problems. We need to build a level-of-detail (LOD) structure and reduce the parameters. It should be a graph in which the points are the strokes and the edges are the error. We need to update the error after each stroke combination.
We need to find an easy and fast method for the error updating. We need to find the better order
Conclusions 44
of simplification. If the graph is built, this will be easy and just simplify from the smallest error edge. With the density measure, we may control the local simplification. We can also find some methods to reduce the computation time. We need to find the correct and faster method to find the series of point pairs to combine the stroke pairs. The calculation of the radius of new stroke is not finished. We have found the central of the thick stroke where the artists want but we did not calculate the radius of the thick stroke. If we have a new method to classify the contour and hatching, we may get the better results. We use the isotropic filter kernel for our simplification.
There are some papers discussed the anisotropic filter [KKD09], and it may produce the better result if we use it.
There are many applications of the stroke simplification algorithm for line drawing. We can apply them to the animation or storyboard. With a series of line drawings, we may find a better way to simplify the strokes. There is another application. We can use the artist drew line-art to guide the simplification of the sketch. We can use the technique such as stroke corresponding [LCY+11]. We may use a database of line-art to simplify the sketch. We can learn more about the drawing style of artists and the style of the strokes. Moreover, the beautification and smoothing of the stroke simplification can let the result be closer to the line-art.
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