S. Teller, " Computing the Antipenumbra Cast by an Area Light Source," SIGGRAPH'92, Vol. 26, No. 2, pp. 139-148, 1992.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....tree is built for. The tree stores cell to cell visibility relation, which also defines the order in which the cells are visited along sightline from the root cell to any destination cell (see figure 1) The above mentioned approach of visibility preprocessing is based on research described in [1, 3, 4]. Since no extensions to existing geometry languages considering the visibility restrictions are known to the authors, it was of a great importance to create a data format to handle the visibility information [2] A B C D E F G G F E C B D p0 p1 p2 p3 p4 p5 p5 p4 p3 p2 p1 A p0 ....

....visible frustum induced by a portal sequence is based on conservative approximation of the anti penumbra, when treating the first portal of the sequence as a light source. The algorithm uses mapping to Plucker coordinates again and invokes the five dimensional convex polyhedra enumeration [4]. Boundary cellA frontCell cellB backCell # the boundary geometry comes here DEF portalA Portal # the portal s location upon the boundary comes here DEF frontCell Cell VisibilityTree VisibilityTree through portalA canSeeCell backCell # more nested VisibilityTree nodes ....

Teller, S.J.:Computing the anti-penumbra cast by an area light source. Computer Graphics (Proc. Annual conference Series 1993), 236-246.

....internal. Examining the 2D faces of the polytope T k h k yields all extremal swaths. However we have to distinguish between penumbral and internal swaths. This distinction can be made locally; that is , by examining the swath s three generator edges and, in turn, their generator polygons. In [21] it is shown how to classify the swath as penumbral or in other case as internal. stabbing line dual of extremal 1D face (edge) 2D face conic trace (dual of 3D swath) other edges Figure 3.14: Duals of 3D swaths as a traces on the Plucker surface in 5D. CHAPTER 3. VISIBILITY DETERMINATION ....

Teller, S. "Computing the Antipenumbra Cast by an Area Light Source." Computer Graphics (Proc. SIGGRAPH'92) 26, 2 (1992), 139-148.

....is moving along a straight line while the camera is moving. The lines drawn from the car are the optical rays of a single point on the car as seen by the moving camera. tersecting line is well known and is also used in graphics algorithms for synthetic illumination and visibility computations (cf. [3]) Having an idea of the minimal number of views required for a solution, we next consider the problem of recovering the piercing line L given k 5 views, known 3 Theta 4 projection matrices (describing camera motion) M i and the projections p i , i = 1; k of the moving point along the line ....

S. Teller. Computing the antipenumbra cast by an area light source. SIGGRAPH, 26(2):139--148, 1992.

....propagation from a source cell S 1 . Figure 4: Visibility propagation from a source cell S 2 . The volume visible to a polygon in the presence of polygonal occluders is, in general, bounded by quadratic surfaces [18] An algorithm for computing this volume was implemented and described in [21], but is not yet sufficiently robust for use on complex models. Consequently, we have developed a simpler algorithm that computes a polyhedral volume guaranteed to enclose the exact visible region. The algorithm is a straightforward construction that, using separating tangent planes, performs a ....

....as Plucker coordinates [20] or simply linespace. Lines in three dimensions correspond to hyperplanes and points in linespace. Any two 3D rays a and b can be oriented by considering their linespace counterparts a , a 5D hyperplane, and Pi b , a 5D point (details of the mapping can be found in [21]) side (a, b) 0 side (a, b) 0 side (a, b) 0 a a a b b b L a P b 5D 3D L a P b L a P b The signed distance of Pi b from a determines the sense in which the lines go around each other in 3D; if Pi b lies on a the lines a and b are coplanar. This sidedness property can be ....

[Article contains additional citation context not shown here]

Teller, S. Computing the Antipenumbra Cast by an Area Light Source. Computer Graphics (Proc. SIGGRAPH '92) 26, 2 (1992), 139\Gamma148.

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S. Teller, " Computing the Antipenumbra Cast by an Area Light Source," SIGGRAPH'92, Vol. 26, No. 2, pp. 139-148, 1992.

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Seth Teller. Computing the antipenumbra cast by an area light source. Computer Graphics (Proc. Siggraph '92), 26(2):139-- 148, 1992.

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