Deformable Bricked Volume Rendering via Hierarchical Visibility
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Solution Overview
Problem
Current direct volumetric rendering techniques face challenges in efficiently rendering deformable volumes larger than graphics memory, particularly with bricking methods, as deformation fields disrupt brick boundaries, necessitate dynamic preprocessing, and destroy information used for empty-space skipping, leading to inefficiencies in rendering and memory management.
Innovation Solution
A method is introduced that compares 3D volumetric voxel datasets to generate a deformation dataset, subdivides the volume into hierarchical cubic bricks and blocks, determines visible blocks, and processes them in visibility order, adding deformation values to render objects, allowing for dynamic deformations across brick boundaries without requiring expensive preprocessing or resampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If brick-based volume rendering is used to handle large volumes exceeding graphics memory, then memory management efficiency is improved, but deformation fields disrupt brick boundaries causing rendering inefficiency
Solution Approach 1:
The volume data is divided into multiple bricks that can be independently loaded into graphics memory. Each brick is further subdivided into blocks for visibility testing. This hierarchical segmentation allows efficient memory management while maintaining the ability to handle deformations by selectively loading and processing only visible blocks after deformation transformation.
2Measurement precision
If deformation fields are applied to volumetric data, then visualization accuracy is improved, but preprocessing complexity and memory usage increase
Solution Approach 1:
The system implements dynamic deformation where the deformation field is applied at render time rather than through expensive preprocessing. The deformation transformation is computed on-the-fly for each block visibility test, allowing accurate visualization without the memory and time costs of pre-deforming the entire volume dataset.
Solution Approach 2:
Instead of physically transforming the volume data through preprocessing, the system uses virtual copying where deformation is applied computationally during rendering. The original volume data remains unchanged in memory, and deformation effects are achieved through coordinate transformation during the visibility test and rendering stages.
3Quantity of substance
If brick boundaries are fixed for memory management, then memory efficiency is improved, but deformation fields crossing boundaries require resampling
Solution Approach 1:
The system changes the parameter space by applying deformation transformations to block coordinates rather than physically relocating data blocks. This allows blocks to virtually cross brick boundaries without actual data movement or resampling, maintaining both memory efficiency and rendering flexibility.
4Productivity
If visible blocks are determined using min-max voxel values, then rendering speed is improved, but deformation fields destroy this information
Solution Approach 1:
The system performs preliminary deformation transformation on block coordinates before visibility testing. By pre-applying the deformation transformation to the block bounding box corners, the system can accurately determine which deformed blocks are visible without losing the min-max information needed for efficient visibility culling.
Data Source
AI summary
A method for rendering a deformable object. The method includes: obtaining a 3D volumetric voxel dataset of a region, such region having therein an object to be rendered; building a tree hierarchical structure for the obtained volumetric dataset, such tree structure blocks as the nodes of a primary tree hierarchy and bricks being those blocks stored as textures in a video memory; augmenting the primary tree hierarchical structure with maximum and minimum values of the data contained within a block; creating a neighborhood tree hierarchy having for each leaf block of the neighborhood tree hierarchy a reference to the neighboring leaf blocks in the neighborhood tree hierarchy as well as references to neighboring bricks in the neighborhood tree hierarchy; updating the information about minimum and maximum in the primary tree hierarchy by saving for each block the minimum and maximum of the neighboring blocks; and rendering the leaf blocks in visibility order.