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→LoD, Mesh size and Framerate
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== LoD, Mesh size and Framerate == | == LoD, Mesh size and Framerate == | ||
Unlike WS2.0 which has a fixed terrain mesh, VPB provides a variety of settings that have a big impact on the eventual terrain mesh. The two main settings (the number of LoD levels, and the ratio of the LoD radius and maximum visible range), have a huge impact on the number of vertices, how the terrain looks, LoD "popping", and framerate. | Unlike WS2.0 which has a fixed terrain mesh, VPB provides a variety of settings that have a big impact on the eventual terrain mesh. The two main settings (the number of LoD levels, and the ratio of the LoD radius and maximum visible range), have a huge impact on the number of vertices, how the terrain looks, LoD "popping", and framerate. | ||
To attempt to understand the relationship, a test was performed. WS30 terrain was generated for a 2x2 degree section of the European Alps bounded by (7E, 45N), and (8E, 47N), with settings as listed below. FlightGear was then run on a desktop with an NVidia GeForce GTX 1660 with 6GB of VRAM. The system appeared I/O limited as GPU utilization was around 30% and on 2GB of VRAM was used. | |||
The following commandline options were used to place the ufo just to the NE of the Matterhorn, facing SW. | |||
--aircraft=ufo --timeofday=morning --disable-real-weather-fetch --disable-ai-traffic --disable-random-objects --disable-random-vegetation --altitude=15000 --prop:/scenery/use-vpb=true --disable-sound --disable-ai-models --prop:/sim/rendering/texture-cache/cache-enabled=false --lat=46.021023 --lon=7.728291 --altitude=12662.75 --heading=226.0 | |||
{| class="wikitable" | {| class="wikitable" | ||
|+ | |+ | ||
Experimental results varying LoD Level and visibility distance ratios | |||
!Dem Resolution | !Dem Resolution | ||
!LoD Levels | !LoD Levels | ||
| Line 61: | Line 65: | ||
!Frame Latency (ms) | !Frame Latency (ms) | ||
|- | |- | ||
| | |90 | ||
| | |8 | ||
| | |7 | ||
| | |0.6 | ||
| | |1099 | ||
| | |4.3 | ||
| | |15 | ||
| | |30 | ||
| | |28 | ||
| | |40 | ||
|- | |- | ||
| | |30 | ||
| | |8 | ||
| | |7 | ||
| | |0.6 | ||
| | |1099 | ||
| | |4.3 | ||
| | |32 | ||
| | |61 | ||
| | |19 | ||
| | |59 | ||
|- | |- | ||
| | |30 | ||
| | |7 | ||
| | |5 | ||
| | |1.2 | ||
| | |785 | ||
| | |6.1 | ||
| | |5.6 | ||
| | |11 | ||
| | |75 | ||
| | |17 | ||
|- | |||
|30 | |||
|7 | |||
|3 | |||
|1.2 | |||
|475 | |||
|3.7 | |||
|3 | |||
|6 | |||
|105 | |||
|14 | |||
|- | |||
|30 | |||
|6 | |||
|5 | |||
|2.5 | |||
|785 | |||
|12 | |||
|4 | |||
|7 | |||
|115 | |||
|13 (a) | |||
|- | |||
|30 | |||
|4 | |||
|5 | |||
|9.8 | |||
|785 | |||
|49 | |||
|3 | |||
|6 | |||
|125 | |||
|12 (b) | |||
|} | |} | ||
Notes: | |||
(a) - Using these settings there was a noticeable reduction in apparent heightmap resolution with a 30m DEM, probably because the resolution of the lowest LoD level was ~40m, compared with 20m for an 7 LoD level mesh. | |||
(b) Using these settings, the terrain resolution was unacceptably poor. | |||
These results suggest that using 7 LoD Levels and a radius of "3" will provide a good balance, with high terrain quality and good frame-rate. | |||
== Running VPB == | == Running VPB == | ||
| Line 118: | Line 160: | ||
-b -4 50 -3 51 \ | -b -4 50 -3 51 \ | ||
--PagedLOD \ | --PagedLOD \ | ||
-l | -l 7 \ | ||
--radius-to-max-visible-distance-ratio | --radius-to-max-visible-distance-ratio 3 \ | ||
-o vpb/w010n50/w004n50/ws_w004n50.osgb | -o vpb/w010n50/w004n50/ws_w004n50.osgb | ||