Early Z Test for Tile-Based 3D Rendering Efficiency
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Solution Overview
Problem
In tile-based three-dimensional rendering, existing methods require unnecessary rendering operations for triangles that are not visible on the screen, leading to inefficiencies and increased power consumption due to frequent external memory access.
Innovation Solution
An early Z test method that performs rendering only on triangles completely included in the first triangle, using a tile-based approach with a small Z-buffer, and employing a half-plane edge function to determine tile inclusion, thereby eliminating rendering for unseen triangles and reducing external memory access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a conventional Z test is performed after completing rasterization for the entire scene, then the Z test can determine which models are visible, but unnecessary rendering operations are performed for triangles that are completely covered by other triangles
Solution Approach 1:
The patent performs a preliminary Z test during the tile binning phase, before completing full rasterization. By comparing the minimum Z value of the current triangle with the maximum Z values of previously processed triangles in the same tile, the system can identify and exclude triangles that are completely covered by other triangles before they undergo full rendering processing, thus eliminating unnecessary rendering operations in advance
Solution Approach 2:
The patent divides the scene into multiple tiles and processes each tile independently. By segmenting the rendering process into tile-based units, the system can perform early Z testing on a per-tile basis, allowing triangles that are completely covered within specific tiles to be excluded from rendering operations while still processing other tiles, thereby improving overall rendering efficiency
2Area of stationary object
If a frame buffer with the same size as screen resolution is used for conventional rendering, then the entire scene can be rendered, but the frame buffer cannot be simply embedded in a chip and requires frequent external memory access
Solution Approach 1:
The patent divides the large frame buffer into multiple smaller tile-based frame buffers, where each tile buffer has a resolution size corresponding to a single tile. This segmentation allows the small tile buffers to be embedded in the chip's internal memory, eliminating the need for frequent external memory access while still supporting rendering of the entire scene through composition of individual tiles
Solution Approach 2:
The patent transitions from a conventional full-resolution frame buffer approach to a tile-based hierarchical structure. By organizing the frame buffer in a tiled dimensionality structure, the system can store multiple tile buffers in internal memory and selectively render only visible tiles, reducing external memory access requirements while maintaining the ability to display the complete scene
3Use of energy by moving object
If tile-based rendering is used to reduce external memory access, then power consumption is reduced, but rendering operations are still performed for triangles that are completely covered by other triangles within tiles
Solution Approach 1:
The patent performs a preliminary Z test during the tile binning phase, before completing full rasterization. By comparing the minimum Z value of the current triangle with the maximum Z values of previously processed triangles in the same tile, the system can identify and exclude triangles that are completely covered by other triangles before they undergo full rendering processing, thus eliminating unnecessary rendering operations in advance
Solution Approach 2:
The patent updates the tile buffer Z value with the maximum Z value of triangles that are completely included in each tile. This preliminary update allows subsequent triangles to be quickly evaluated against the existing tile buffer Z value, enabling early exclusion of covered triangles before full rendering, thus improving rendering efficiency while maintaining the tile-based low-power architecture
Data Source
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AI summary
A method and system for an early Z test in a tile-based three-dimensional rendering is provided. In the method and system for an early Z test, a portion which is not displayed to a user is removed prior to performing a rasterization process, and thereby performing the 3D rendering efficiently. The method includes segmenting a scene into tiles for performing a rendering with respect to a triangle; selecting a first tile of the tiles, which has a tile Z value less than a minimum Z value of the triangle; and performing the rendering with respect to the triangle in remaining tiles excluding the selected first tile of the tiles.