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| Both sides previous revision Previous revision Next revision | Previous revision | ||
| realtime:screenspace [2026/04/16 19:15] – [Key Consequence] mh | realtime:screenspace [2026/04/16 19:19] (current) – [Core Concept] mh | ||
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| Instead of computing how light interacts with geometry, they **reuse what the camera has already rendered** and manipulate it to produce the desired visual result. | Instead of computing how light interacts with geometry, they **reuse what the camera has already rendered** and manipulate it to produce the desired visual result. | ||
| - | <WRAP center tip> | + | |
| - | **→ If it is not visible on the screen, it does not exist.** | + | |
| - | </ | + | |
| Line 70: | Line 69: | ||
| ===== Screen Space Materials ===== | ===== Screen Space Materials ===== | ||
| - | A Screen Space material ignores object-based shading and instead displays content aligned with the camera view. | + | A Screen Space material |
| → geometry becomes a canvas | → geometry becomes a canvas | ||
| Line 104: | Line 103: | ||
| ===== Screen Space Reflections (SSR) ===== | ===== Screen Space Reflections (SSR) ===== | ||
| - | SSR uses screen space to approximate reflections. | + | **SSR** uses screen space to **approximate reflections**. |
| Instead of tracing rays in 3D: | Instead of tracing rays in 3D: | ||
| - | → sample the already rendered image | + | |
| - | → reuse visible pixels as reflection data | + | → reuse visible pixels as reflection data |
| - | Limitations: | + | === Limitations: |
| * cannot reflect off-screen objects | * cannot reflect off-screen objects | ||
| Line 117: | Line 116: | ||
| * unstable in fast motion | * unstable in fast motion | ||
| - | Relation to Screen Space materials: | + | === Relation to Screen Space materials: |
| * same coordinate system (screen space) | * same coordinate system (screen space) | ||
| Line 126: | Line 125: | ||
| ===== Other Screen Space Techniques ===== | ===== Other Screen Space Techniques ===== | ||
| - | Common siblings: | + | === Common siblings: |
| - | * SSAO → fake contact shadows using depth | + | |
| - | * Screen Space Refraction → distort background using screen data | + | |
| - | * SSGI → approximate bounced light | + | |
| - | * Screen Space Shadows → cheap shadow approximation | + | |
| - | * Screen Space Decals → project textures after rendering | + | |
| - | All share: | + | === All share: |
| - | → operate on the final image | + | |
| - | → avoid expensive world simulation | + | → avoid expensive world simulation |
| ===== Real-Time Philosophy ===== | ===== Real-Time Philosophy ===== | ||
| - | Screen Space is part of a larger doctrine: | + | Screen Space is **part of a larger doctrine**: |
| < | < | ||
| Line 148: | Line 147: | ||
| </ | </ | ||
| - | In real-time systems: | + | === In real-time systems: |
| - | → simulation is expensive | + | * simulation is expensive |
| - | → approximation is common | + | |
| - | → screen space is strategic control | + | |
| ===== Practical Use (Immersive / Media Servers) ===== | ===== Practical Use (Immersive / Media Servers) ===== | ||
| - | In immersive environments, | + | In immersive environments, |
| Used for: | Used for: | ||
| Line 166: | Line 165: | ||
| * stable overlays and UI elements | * stable overlays and UI elements | ||
| - | Key advantage: | + | === Key advantage: |
| - | → What you see = what you output | + | |
| Line 178: | Line 177: | ||
| * no depth awareness beyond visible data | * no depth awareness beyond visible data | ||
| - | Use when: | + | === Use when: === |
| - | → control > realism | + | |
| ===== Final Rune ===== | ===== Final Rune ===== | ||
| - | Screen Space techniques do not simulate the world. | + | Screen Space techniques |
| - | They control what the audience perceives, using only what is already visible. | + | They **control what the audience perceives**, using only what is already visible. |
| - | → Geometry becomes support | + | |
| - | → The screen becomes truth | + | → The screen becomes truth |