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Optimizing Background Rendering for Large Outdoor Scenes in 3D Graphics

This paper discusses techniques to optimize background rendering in large outdoor scenes, addressing challenges like depth buffer limitations and projection volume issues. It presents the view frustum concept, which decreases rendering overhead by excluding off-screen objects and employing advanced methods like pre-computed backgrounds, skyboxes, and layered depth images. By dynamically generating backgrounds and showcasing parallax effects, the research aims to enhance realism while working in real-time. The goal is to seamlessly transition between background and foreground elements in complex 3D environments.

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Optimizing Background Rendering for Large Outdoor Scenes in 3D Graphics

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  1. Background Caches for Large Outdoor Scenes Bill Hess

  2. Motivation:

  3. Motivation:

  4. View Frustum • Volume enclosed by 6 planes • Objects outside the frustum are not drawn • Back plane decides how deep the scene is

  5. Problem: Depth Buffer • Geometry depth is stored at every pixel • Allows objects to be drawn in any order • Allows objects to intersect each other • Depth buffer precision is fixed in hardware • Multiple scene depths can map to one depth buffer value • As the back plane is pushed back, the range of values that can map to the same depth value increases

  6. Problem: Depth Buffer

  7. Problem: Projection • View Frustum volume increases with the cube of the scene depth • Potentially 8 times more geometry to draw just to double scene depth

  8. Solution • Draw backgrounds less frequently • Draw background as a flat image • Common methods • Render/Draw backgrounds ahead of time • Render backgrounds into a texture at run-time

  9. Skybox • Scene surrounded by a textured cube • Cube is textured with a backdrop representing the background • Cube does not move with the scene • Appears “infinitely” far away

  10. Skybox limitations • Players can never reach the background • Gap between foreground and background • No parallax effect • Really only good for… sky.

  11. 3D Skybox • Used in Valve’s Source engine • Background geometry is drawn to 1:16 scale in a hidden part of the map • Camera is placed into the “skybox” to render the background • Use the depth buffer twice • Background is only a mockup, not explorable

  12. Related Research • Pre-Computed backgrounds • Scene is broken into view-cells • Backgrounds are stored on disk • City walkthrough • Buildings are rendered to flat Impostors • Camera is constrained to street tracks

  13. Layered Depth Images • Render scene but record multiple colors and depths at each pixel • Use inverse camera transformation to reposition each pixel for a new camera angle • Parallax effect • Hidden surfaces are revealed • Storage required equal to depth complexity of the image (max number of overlapping objects)

  14. Goal • Dynamically generate background images • Show parallax for view changes • Transition between background and foreground • Work in real-time • Combination of Skybox and Layered Depth Image

  15. Work So Far • Recreate the problem

  16. Work So Far

  17. Work So Far

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