Paper -5 Multiresolution volume visualization with a texture-based octree ImmaBoada, IsabelNavazo, Roberto Scopigno

Introduction New texture memory management policy Octree representation of original data ,computed during preprocessing At render time set of octree nodes selected User defined criteria about accuracy and importance of data View independent and takes advantage of data homogenity, importance

Approach A hierarchical data organization has been adopted in the context of a texture-based volume rendering system in, where texture bricks at different resolutions can be assigned to sections of the original dataset. An improved rendering solution, based on the use of spherical shells instead of view-aligned planes Texel values represent density values and gradients

Rendering Octree built in pre-processing phase, traversed at rendering time. Bunch of nodes called ‘cut’ is selected Resolution of texture brick determined at runtime N(i)B(i) : according to homogenity, importance and degree of accuracy and surrounding regions

Error calculation

Cut selection For each node ni at level k, we have a corresponding subtree of depth lmax −k and a corresponding voxel region of resolution 2^Lmax−k ∗2^Lmax−k ∗2^Lmax−k. The accuracy of the texture-based representation is encoded in the node’s corresponding nodal error, εR(ni) = εp(ni).

Octree traversal Error threshold Node importance Importance function Uniformity function E* =Eu / Imp(ni,f). function OTcut(IN : OT_node, εu, f, Tmax, minPartSize; OUT : brick_set) Start with root node and trace along all children till a solution is found

Results

Questions?