## 4 Results  
The method can be controlled using several attributes, such as the number and radius of the faults, number and hardness of materials, and impact of erosion. Choosing a too small radius or fault number in relation to the size of the model leads to visually implausible results. In this case, the model has more random peaks or mounds than terrain formation. The experiment shows that a radius greater than 10% of the size of a height-field's smaller side gives more adequate results then the one out of this range (Figure 15). The classification of materials is not limited and theoretically may contain an infinite number, but from a practical side too much value reduces their importance if these are evenly distributed in relation to the model height (Figure 16). However, more materials allow the control of the terrain caprock's size to a greater extent. By assigning the same hardness to several materials from the top, it is possible to adjust the height of the durable core (Figure 17). Figure 14: Sample butte generated by circular faults limited along the x-axis (grid resolution: \(1024\ \times\ 1024\); fault radius: \(1\leqslant r\leqslant 350\); total faults: 250). Erosive model was obtained for \(E=0.45\) and \(\rho=5\). (**a**) Initial geometry. (**b**) Initial map. (**c**) Material layer (\(mat=3\)) interpreted as a grey-scale map. (**d**) \(mat=3\) without caprock. (**e**) \(mat=3\) with caprock. (**f**) Material layer (\(mat=5\)) interpreted as a grey-scale map. (**g**) \(mat=5\) without caprock. (**h**) \(mat=5\) with caprock. Figure 15: Comparison of the impact of the fault radius on the model geometry (grid resolution: \(100\times 100\); fault height (max in centre): \(0\leqslant\Delta h\leqslant 1\)). (**a**) \(r=3\). (**b**) \(r=10\). (**c**) \(r=25\). The experiments show that material hardness selection provides more plausible results if the next one is not less than the previous one, counting from the model base. Omitting this dependence can lead to model calderisation, which is not preferred in table mountains' modelling (Figure 18). It is worth emphasising that, compared to the LFF, the CFF method is characterised by a plausible reception due to the intended purpose of modelling. The obtained results using the linear version are more adequate for rocky or boulder formations than structured landform. Circular-base results are characterised by less roughness of geometry and better provide the soil sediment arrangement in mesa  
Figure 16: Comparison of the impact of the materials number on the model geometry (grid resolution: \(100\times 100\); fault height (max in centre): \(0\leqslant\Delta h\leqslant 1\)). (**a**) \(mat=3\). (**b**) \(mat=6\). (**c**) \(mat=9\). Figure 17: Comparison of the impact of the combination of materials’ hardness on the model geometry shown in Figure 16c. (**a**) 2 top materials combined. (**b**) 4 top materials combined. (**c**) 6 top materials combined. formations. The main limitation of the method is the problem of an appropriate selection of the radius for the fault circle. It is closely related to the size of the model. A too-small radius leads to unnatural (or rare in nature) results. On a smaller impact, a similar problem also occurs in the case of the wrong selection of the number of faults. Another issue is that the caprock modification provides near-vertical cliffs that can lead to artefacts in the rendering process. Near-vertical structures are generally undesirable in height-field based terrains. This restriction can be removed in volumetric representation. The example of a textured and rendered butte-like final asset with the application of the proposed approach is presented in Figure 19. Several examples in the orthographic projection of generated mesa-like assets are shown in Figure 20. The butte-like objects are shown in Figure 21.  
Figure 19: Textured and rendered in a Terragen butte-like asset obtained by the proposed method (grid resolution: \(150\times 150\), fault radius: \(1\;\leqslant\;r\;\leqslant\;35\); total faults: 35 along x-axis).