X-Plane Flight Simulator – Tuning The Graphics

CH 750 Ready For Takeoff

I was looking for a realistic flight simulator so I could practice stalls and slips. After a bit of a romp around the ‘net I rediscovered X-Plane by Laminar Research. I had tried it before but my computer and graphics card weren’t powerful enough and I couldn’t get it to run at a high enough frame rate. As a result, I abandoned it. I have a newer computer and graphics card now so it was worth having another look at the software.

I downloaded the demo version (10.X) from their web site and tried it out. The simulation was working well but I had to disable a lot of the rendering options in order to get the frame rate up. My computer has 8 CPUs so computing power wasn’t the issue. The obvious culprit was the video card. I found a more powerful graphics card that wouldn’t break my budget, and the performance increased dramatically.

My current system configuration:

I7 Microprocessor (8 CPUs) with 12 Gigabytes of memory.
Radeon HD 6670 Video Graphics Card.
24 inch video monitor.
Saitek EVI Force joystick
Saitek Proflight Rudder Pedals
X-Plane Version 10.X installed from DVDs and upgraded via the ‘net.

X-Plane Video Capture

One of the cool features of X-Plane is the video capture mode. Use CTRL+SPACEBAR to toggle it on and off. The movies will be placed in X-Plane’s base folder, and they’re numbered in sequence to prevent file collisions. I’ve thrown in a relatively short clip where I’m landing the CH 750. The best part is that the movies can be reviewed later so you can pick out your mistakes (and the stuff you did right.)

Tuning X-Plane’s Rendering Options

The objective is to get as much performance from the graphics card as possible while keeping the frame rate high enough to allow the simulation to flow smoothly. In other words, if you enable a rendering option it will reduce the frame rate, so you’ll need to pick and choose the options that you want and sacrifice the ones that place too great a load on the system.

The procedure involves disabling all of the rendering options and then running the simulation to get the ‘no load’ or baseline frame rate. Once the baseline has been established, begin enabling rendering options one at a time in order to determine their impact on the frame rate.

Disable the options that cause a 5 or more frame per second drop in the frame rate. These options are the expensive ones in terms of the demands they make on the system, so we’ll leave them for last and re-enable them if the frame rate allows it.

If the frame rate budget is limited it may be necessary to compromise and leave some options disabled if the system can’t tolerate the load.

Tuning Procedure

Establish the baseline or ‘no load’ frame rate by turning off all of the rendering options and running the simulation:

Run X-Plane.
Press the ‘P’ key to pause the aircraft while you make adjustments.
Go to Settings->Data Input & Output.
Click the rightmost check box beside ‘framerate.’ This will cause X-Plane to display the current instantaneous frame rate at the top left of the screen.
Exit the Data Input & Output properties page.

The screen capture (left) shows the check box that must be set in order to display the frame rate in the simulation. The screen capture (right) shows what should appear on the screen. The first column (f-act) contains the frame rate measurement. In this case, the value is 54.47 frames per second.

Disable all of the rendering options, AI traffic and simulated weather. The screen captures show what I had set in my flight simulator (click on the image to see the full size version):

Turn off as many rendering options as possible:

Go to ‘Settings->Operations & Warnings’, and make sure that the ‘Flight Models Per Frame’ value is set to ’01′. Go back to the simulation and take a look at the frame rate:

No Load (Baseline) Frame Rate

My system was rendering approximately 70 frames per second with the simulation paused. The frame rate dropped to about 65 FPS when the simulation wasn’t paused.

Working Through The Options

Go to Settings->Rendering and pick an option to enable. It doesn’t matter which one because you need to work through them all eventually. Return to the main window and fly the plane while you check the frame rate. The new value shows how that option is impacting your system. Some helpful hints:

Work with one option at a time to avoid confusion.
Turn the option on and check the frame rate.
Turn the option off again and check the frame rate. If the frame rate doesn’t return to it’s previous value you’ll have to restart the program (exit and start over) in order to clear out any residual goo the setting may have caused.

When I reviewed the rendering options on my system, I found that the following items had a significant impact on the frame rate:

Simulated weather. For example: wind, clouds, wind shear, precipitation. These settings may be found in Environment->Weather.
Any setting that deals with particles such as clouds or mist.
Roads and car traffic.
Rendering shadows and some other lighting effects.
Anti-alias value set too high.
Anisotropic value set too high.
Models Per Frame set too high (Settings->Operations & Warnings).

Basic Options for >60 FPS

I found that I could keep my system’s frame rate above 60 by turning off all weather effects, leaving the Models Per Frame at 1, and using the settings shown in the screen capture shown above.

Budgeting for ‘Expensive’ Options

Now that I know which options place the greatest load on my system (your system may be different depending on the CPU and graphics card) I can budget the remaining frame rate to include the ones that I want most (The remaining frame rate is the difference between the current frame rate and the minimum frame rate required to achieve smooth movement in the simulation.)

For example, if I add scattered cumulus clouds at 18,000 to 20,000 feet the sky takes on a more realistic appearance, but the frame rate decreases from 60 FPS to 40 FPS. I decided to keep the frame rate at or above 30 FPS, so my remaining budget is 10 FPS.

It’s possible to go lower than 30 FPS, that’s just my personal preference (at the moment.) Some more experimentation may show that I can go lower and still achieve good results…

If The Baseline Frame Rate is Too Low?

If the baseline frame rate is between 20 to 30 FPS when all of the options are disabled, you need to decide if you can live without the other rendering options or to upgrade your video card.

I was using a Sapphire HD 2600 PRO video card but the best rate I could achieve was 30 FPS with a limited number of rendering options. I decided to replace it with an HD 6670 and the baseline frame rate increased to 70 FPS. When I finished screening the options the frame rate was over 60 FPS, giving me a 30 FPS budget for add-ons.

Conclusion

X-Plane takes a little effort to configure but the results are worth it. The graphics are great and the flight model is very realistic, but it needs a good graphics card to work properly.

As a side note, I can run my RealFlight 5.5 with all of the graphics options enabled and it doesn’t load this card down at all.