3D Rendering Z Buffer Flickering Prevention via Depth Offset
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Solution Overview
Problem
Existing three-dimensional image rendering techniques using Z buffers suffer from flickering due to errors in depth value calculations, particularly when objects and their shadows are rendered close to each other, leading to inaccuracies and deviations from the intended design.
Innovation Solution
A rendering processing apparatus that employs perspective projection transformation and depth comparison using a Z buffer, where the calculation parameter is adjusted to ensure that the depth value of certain polygons is closer to the virtual camera than others, without transforming the polygon model, thereby preventing flickering by altering the near and far clip plane values or adding an offset to the depth value.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polygons are rendered with slightly floated positions to create realistic shadows and boundaries, then the three-dimensional image realism is improved, but Z buffer depth value accuracy deteriorates causing flickering
Solution Approach 1:
The patent changes the depth value parameter calculation by modifying the perspective projection transformation formula. Specifically, it adjusts the near value (n) and far value (f) parameters in the Z value calculation equation, and introduces a depth offset parameter to shift depth values for specific polygons. This parameter modification ensures that even when polygons are positioned close to each other (such as shadows near ground), their depth values remain distinguishable in the Z buffer, preventing flickering while maintaining rendering realism
2Measurement precision
If the Z buffer resolution is increased to improve depth value accuracy, then flickering is reduced, but processing cost and memory usage increase
Solution Approach 1:
Instead of increasing Z buffer resolution, the patent modifies the depth value parameters in the perspective projection transformation. By adjusting the near/far clip plane values and introducing depth offsets, the system achieves better depth discrimination with the existing Z buffer resolution, avoiding the computational and memory costs associated with higher resolution buffers
3Measurement precision
If polygon positions are transformed to prevent flickering, then depth rendering accuracy is improved, but the original design and position information is lost
Solution Approach 1:
The patent segments the rendering process into two independent parts: geometric positioning and depth value calculation. Polygon positions in three-dimensional space remain unchanged, preserving the original design. However, the depth values used for Z buffer comparison are separately adjusted through parameter modifications in the perspective projection transformation. This segmentation allows position information to be preserved while depth rendering accuracy is improved
Solution Approach 2:
The patent introduces depth offset parameters as an intermediary between the original polygon positions and the final depth values stored in the Z buffer. This intermediary layer allows the system to compensate for depth value inaccuracies without altering the actual polygon positions, thus preserving design information while achieving accurate depth rendering
Data Source
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AI summary
In an image processing for rendering a three-dimensional virtual space by using a perspective projection transformation and a depth comparison that uses a Z buffer, firstly, polygons to be rendered in a rendering process of one frame are classified into a first-type polygon and a second-type polygon. Next, the rendering process is performed for the first-type polygon. Subsequently, at least one of a near value and a far value of a clip space is set to a value different from a value used in the rendering process for the first-type polygon. The rendering process for the second-type polygon is performed by using the clip space having at least one of the far value and the near value having been set to the value different from the value used in the rendering process for the first-type polygon.