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Depth range from the ground: far bodies, their orbits and rings tie or invert in the 24-bit depth buffer

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评估

难度
5/5
预计耗时
一周以上
新手友好度
35/100
Issue 类型
缺陷
描述清晰度
基本清楚
活跃度
活跃
技术栈
javascript, three.js
领域
computer-graphics

调研方向

Start by reading the depth-buffer and projection setup, then check the composite and Cesium depth handoff described in CESIUM.md and portal-netgl. Compare reversed-Z, logarithmic depth, and analytic occlusion against the stated telescope-FOV cases; done means Jupiter occludes the far halves of its moons' orbits, Saturn occludes its far ring arc, the Moon hides background stars, and space views retain parity.

由索引模型根据 Issue 内容生成。

描述

track:rendering

Found while fixing the atmosphere dashes over Jupiter (#174).

Problem

From Earth's surface the near plane is ~100 m, so every body beyond a few million km lands on or one 24-bit step under the far plane. Depth can then no longer order them:

  • Orbits over their planet: Ganymede's orbit line ties with Jupiter's disc, and overlays pass the depth test on a tie, so the far half of the orbit draws across Jupiter (telescope FOV from the ground).
  • Rings: Saturn's far ring arc draws over the disc from the ground.
  • The Moon and stars: catalogue stars, pulled to 0.999999·w, sit nearer than the Moon from the ground (≈0.9999995), so a bright star behind the Moon could show through it.

#174 fixed the atmosphere pass's own misreading of these depths; the ordering problem remains.

Options

  • Reversed-Z with a float depth buffer (WebGL2: DEPTH_COMPONENT32F plus a reversed projection): near-uniform relative precision over the whole range. three.js supports reverseDepthBuffer (r163+); check the composite and Cesium's depth handoff (CESIUM.md) and portal-netgl.
  • Logarithmic depth (three's logarithmicDepthBuffer): simple, but writes gl_FragDepth, which costs early-z and touches every custom shader.
  • Analytic occlusion: overlays and background test against the bounding spheres of nearer bodies in the shader. Targeted, no buffer change.

Done when

From Earth's surface at a telescope FOV, Jupiter hides the far half of its moons' orbits, Saturn's disc hides the far ring arc, and the Moon hides the stars behind it; nothing changes in space views (parity).

Generated by Claude Code

主要语言
JavaScript
星标
55
派生
4
平均合并
9 小时 32 分钟
30 天内合并 PR
136

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