Figure 4.7: The figure to the left demonstrates a geological model containing all the features that can
be sketched in this prototype. The figure to the right is the modeling result of one of the participants in the user-study. This figure shows very well the procedural deposition from the river into the sea. Both images are courtesy of Morten Bendiksen.
A domain expert from the petroleum industry that has evaluated this work pointed out the lack of support for sketching faults, which are important if the 3D sketching should be applied to a broader geological sketching audience. In addition, he em- phasized that annotations are important and pointed out that they were missing in our reproduction in Figure4.8. Finally, he asked for the possibility of changing the size of the box-proxy geometry. Our proxy geometry does not support this today. Despite of these drawbacks, he definitely thinks that this approach of sketching 3D models is an approach worth more investigations.
The procedural deposition modeling, as shown in Figure4.7, was not as much ap- preciated by the domain experts as we expected. The main reason for this is that the deposition process can be very complicated to describe procedurally and a simplified version may not be able to produce sufficiently good results. They suggested leaving it to the model author to sketch the deposits explicitly. That said, the consensus was that the combination of explicit and procedural modeling could be useful, only that we did not pick the optimal case to show it. As an example, domain experts have rec- ommended us to experiment with shaping the rivers procedurally (straight or winding, narrow or wide) based on the terrain through which they flow.
4.3 Revealing Internal Features in a 3D Geological Model
Last demonstration in this chapter shows how to reveal internal features in a geological model utilizing our oblique illustrative cutaway visualization technique. The demon- stration is published in PaperC; please refer to this paper for further details.
The 3D models produced in the prototypes described in Section4.1and Section4.2
do not yet include internal features hidden by the surrounding context. Therefore, the model in this demonstration represents the dense-data scenario and it is obtained from a reservoir model. The model utilized for this demonstration is from the Ness-formation in the Oseberg-field, obtained from our collaborators at Statoil. Its focus features are sand-filled channels, ancient rivers and deltas with excellent reservoir properties, see
Figure 4.8: This figure shows the comparison of a geological story created by a geology illustrator (to
the left) and the same story reproduced in our 3D sketching prototype. Although it is not possible to reproduce the story illustrations exactly, the overall story is reproduced. Images to the left are courtesy of Haakon Fossen. Images to the right are courtesy of Morten Bendiksen.
Figure4.9(left). The model is created in the domain application system IRAP RMS. Even though this is a matured tool, the visualizations of such models it provides are very elementary. To study the channels together with the geological layer context, the channels are projected onto the underlying geological surface, as Figure 4.9 (right) shows. Thus, the spatial ordering and actual positions of the channels are lost, and have to be reconstructed in the mind of the viewer.
4.3.1 Cutaway Visualization of 3D Geological Models
The goal of this project was to synthesize geological illustration, such as showing in Figure3.16, from computerized geological models. The Ness model is very wide and long, compared to the depth. The geological layer-cake cutaway illustrations we want to reproduce, typically have a cube shape. We have therefore, cropped the Ness model around some potentially interesting channel structures and utilize this sub-model to
4.3 Revealing Internal Features in a 3D Geological Model 43
Figure 4.9: The figures show how the Ness formation is visualized in in the domain specific application
called Roxar Reservoir Management Software (RMS). The figure to the left shows all the modeled channels in the formation, but this visualization cannot show the context around the channels. The figure to the right shows how the channels are depicted together with the context in this tool. Here the channels are projected onto the horizon surface, thus the spatial information of the channel locations is lost.
illustrate our cutaway method1.
Applying our cutaway visualization design principles to the Ness geological model produces visualization as shown in Figure4.10(right). By comparing this image with the visualization of the same model utilizing our implementation of a previous state of the art method [10], shown in Figure4.10(left), reveals that our oblique cutaway visualization offers better communication of: how deep into the model the channels are located; how the channels relate to the bottom surface of the geological layer they reside in (the orange layer); the spatial ordering of the focus features. All this information is difficult, if not impossible, to perceive from the left image.
Our cutaway visualizations are constructed in real-time; and, since it requires a two- pass rendering it runs at approximately 50% of the frame-rate compared to rendering the model without the cutaway visualization.
4.3.2 Discussions
We have demonstrated the cutaway visualizations of the Ness geological model to do- main experts. They all emphasize the benefit of showing the focus features together with the context and they confirmed the increased perceptual improvements of our vi- sualization. A formal user-study is needed to confirm properly that this holds for the general case of 3D geological model visualization and whether there are additional de- sign principles that we have not yet discovered.
The fact that we cannot yet produce 3D models with inside “hidden” features with our sketching prototypes, prevents us from demonstrating the power of all our tech- nical contributions on one complete example. However, projecting the sketching-for- geology concept, introduced in this dissertation, towards the future predicts that such synthesized models will be available, and then the illustrative cutaway visualization will be an important occlusion management technique.
Figure 4.10: The figure to the left shows our implementation of the cutaway method by Burns et al. [10] applied to the Ness geological model. It exemplifies one of the perceptual problems we observed with current cutaway methods; it looks like the geological channels are located in the yellow-colored top layer, while in fact they are all residing in the orange, third layer. The figure to the right shows a cutaway visualization based on our design principles. In this picture we more clearly see in which layer the geological channels resides, how the channel shapes corresponds to the shape of the surrounding context, and the depth of the cutaway.