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AI Traffic: Difference between revisions
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** '''a).''' added to each vertex as an vertex attribute - every type of object is combined in one vertex buffer and rendered with the same shaders, texture atlas or array, material parameters that change between objects or within objects like specularity as as vertex attributes or textures, and a shader that can handle all object animations, The entire set of objects takes up one scene graph node. It's possible to do ground vehicles and aircraft as two meshes. | ** '''a).''' added to each vertex as an vertex attribute - every type of object is combined in one vertex buffer and rendered with the same shaders, texture atlas or array, material parameters that change between objects or within objects like specularity as as vertex attributes or textures, and a shader that can handle all object animations, The entire set of objects takes up one scene graph node. It's possible to do ground vehicles and aircraft as two meshes. | ||
** '''b).''' added to a per-instanced vertex attribute - each different type of object (different ground vehicle) is instanced and takes up one scene-graph node (this can allow different shaders and textures per object type), | ** '''b).''' added to a per-instanced vertex attribute - each different type of object (different ground vehicle) is instanced and takes up one scene-graph node (this can allow different shaders and textures per object type), | ||
* The vertex shader can trivially look at the object ID, path segment, the starting time, speed scaling factor, and current time to position each object. If the current time is past the end of the path, | * The vertex shader can trivially look at the object ID, path segment, the starting time, speed scaling factor, and current time to position each object. If the current time is past the end of the current path, the object will stay at the end position. | ||
* The buffers can be a uniform array (minimum of points in each path segment and more smoothing), Uniform Buffer Object (UBO - not available until Vulkan due to Macs not supporting it), a Texture Buffer Object (TBO - Mac support unknown), or a texture looked up in a vertex shader (maybe slower). | * The buffers can be a uniform array (minimum of points in each path segment and more smoothing), Uniform Buffer Object (UBO - not available until Vulkan due to Macs not supporting it), a Texture Buffer Object (TBO - Mac support unknown), or a texture looked up in a vertex shader (maybe slower). | ||
* Data format: Each path segment is x,y,z position at regular times - a time-series of positions - e.g. [10m, 20m, 0m elevation] at t = 1s. [20m, 25m, 0m] at t=2s . [30m, 30m, 0m] at t= 3s. 16 bit integers are enough, but 32 but floats can also be used at the cost of 2x the occupancy. 16 bit implementation: If a texture is used it can be 16bit RGB - R=x, G=y, B=z. 2 consecutive 8 bit values can also be read from a texture.16 bit integers can cover an ground traffic area of ~65km with a spacing of 1m. 16bits can give a ~13km ground traffic area with an accuracy of 20cm. The accuracy of the positions doesn't matter too much - the vertex shader can look at 2-3+ path positions and create a smooth interpolation (a smooth curve joining the points). The time steps can also be large. | * Data format: Each path segment is x,y,z position at regular times - a time-series of positions - e.g. [10m, 20m, 0m elevation] at t = 1s. [20m, 25m, 0m] at t=2s . [30m, 30m, 0m] at t= 3s. 16 bit integers are enough, but 32 but floats can also be used at the cost of 2x the occupancy. 16 bit implementation: If a texture is used it can be 16bit RGB - R=x, G=y, B=z. 2 consecutive 8 bit values can also be read from a texture.16 bit integers can cover an ground traffic area of ~65km with a spacing of 1m. 16bits can give a ~13km ground traffic area with an accuracy of 20cm. The accuracy of the positions doesn't matter too much - the vertex shader can look at 2-3+ path positions and create a smooth interpolation (a smooth curve joining the points). The time steps can also be large. | ||
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From a quick google search - a 2010 blog about whether UBOs or TBOs are more suited for different tasks: | From a quick google search - a 2010 blog about whether UBOs or TBOs are more suited for different tasks: | ||
''"Personally I use them for instanced rendering by storing the model-view matrix and related information of each and every instance in a common uniform buffer and use the instance id as an index to this combined data structure. This usage performs very well on my system.'' | ''"Personally I use them [UBOs] for instanced rendering by storing the model-view matrix and related information of each and every instance in a common uniform buffer and use the instance id as an index to this combined data structure. This usage performs very well on my system.'' | ||
''Also uniform buffers can be used to store the matrices of bones and use them for implementing skeletal animation, however, I personally prefer using normal 2D textures for this purpose to take advantage of the free interpolation thanks to the dedicated texture fetching units but that’s another story." - Rastergrid blog, 2010 [https://www.rastergrid.com/blog/2010/01/uniform-buffers-vs-texture-buffers/][https://web.archive.org/web/20211119134448/https://www.rastergrid.com/blog/2010/01/uniform-buffers-vs-texture-buffers/]'' | ''Also uniform buffers can be used to store the matrices of bones and use them for implementing skeletal animation, however, I personally prefer using normal 2D textures for this purpose to take advantage of the free interpolation thanks to the dedicated texture fetching units but that’s another story." - Rastergrid blog, 2010 [https://www.rastergrid.com/blog/2010/01/uniform-buffers-vs-texture-buffers/][https://web.archive.org/web/20211119134448/https://www.rastergrid.com/blog/2010/01/uniform-buffers-vs-texture-buffers/]'' | ||