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Realism and Performance
Published in Aditi Majumder, M. Gopi, Introduction to Visual Computing, 2018
Bounding Sphere: Bounding spheres can also be used as bounding volumes. In this case, the intersection computation becomes even simpler. First it is detected whether the center of the sphere is inside or outside the plane. Next the distance of the center of the sphere from the plane is computed. If this is smaller than the radius, then the object is intersecting with the view frustum. If the distance is bigger than the radius, then the object is accepted or culled based on its center being inside or outside the plane respectively. Bounding spheres are not affected by the rotation of the enclosed object, and if the object is translated, the bounding sphere is also translated by the same amount. So it is easy to update the bounding sphere with rigid transformations of the enclosed object.
Measurement of entrained air-void parameters in Portland cement concrete using micro X-ray computed tomography
Published in International Journal of Pavement Engineering, 2018
Haizhu Lu, Karl Peterson, Oleksiy Chernoloz
Taking these results into account, it was decided to filter out (remove) any 3D voids with a minimum x, y, z diameter <3 pixels, since it is practically impossible to assess accurately the shape of such small objects. This minimum diameter cut-off (Thdmin) of 3 pixels effectively removed all voids < 22.5 μm in diameter from the analysis. Furthermore, it was decided to treat 3D voids with a minimum diameter between 3 and 6 pixels differently than larger voids in terms of the spherical solidity criteria used to distinguish air-voids from voids in aggregate. Voids with a minimum diameter between 3 and 6 pixels were assigned spherical solidity criteria (Ths1) that were slightly lower than the spherical solidity criteria for larger voids (Ths2). This distinction was made to account for the consistent underestimation of true spherical solidity for voids in the 3 to 6 pixel diameter range. For the purpose of computing efficiency, five surface points were selected on each object to calculate the bounding sphere. From qualitative observations of Figure 8, a value of 0.70 was initially selected for Ths1, and a value of 0.75 was initially selected for Ths2. As described later in Section 3.2, an uncertainty analysis was carried out to test the validity of the selected spherical solidity criteria.