P3D v4 Night Textures Question


I was attempting to tweak some dds texture files on some airport buildings but got some unexpected results. I had assumed that the *_lm.dds textures were simply replacement textures for the daytime ones, but it seems that some kind of blending is going on between day and night textures, that results in a brighter highlights. Is this correct?

As a test I used the same texture for a yellow window glow for both night and day, and the night version was much lighter and harsher than the day version which seemed dull in comparison. The only thing I could think of was texture blending, but I don't really know what the sim is doing with lm textures. It could also be the result added ambient colour to lms, or i might be totally wrong and some unknown light source was illuminating it. I'm trying to find an explanation for this if anyone can help!

Cheers Jason


Resource contributor
It does not seem natural to me that a window would glow in daylight, it seems like the brightest possible interior illumination would make a darkened room, approximately ambient light intensity, with possibly a yellow tint to it. In truth, many fully lit rooms will still appear dark from outside in daylight.
You might want to review other night textures because at night, that same light would again be approximately the intensity of daylight, albeit the surrounding building areas would be dramatically darker.

Compare the two images below. You will notice that the light glow is pretty much exactly the same color of the daytime pool water color. The house has dark windows during daytime and yellow, not glowing, windows at night.

Yes there is blending. Daytime textures show slightly through night ones, however it's barely visible and I just incorporate it into my night texture procedure. As a general rule, to become night textures, my day textures get overall dimming via a Photoshop layer of black, with approximately 80% opacity for FSX, 90% P3D, although in practice, you can make the same texture work in both. For most windows, I usually just leave the daytime color and that becomes an excellent illuminated night.
Thank you for your help.

It seems that the blending is based on some kind of multiply which makes the lighter colours (ie lights) much stronger at night, but doesn't affect the darker colours so much.

The yellow window was only a test and is nothing I am going to use. The actual problem is a terminal interior which is lit at night but which also needs to be lit during the day, especially if it's a grey or rainy day. I can make it look good during the day, by using a bright texture, but at night this becomes too intense. I guess it's just a question now of experimenting with that night texture until it looks right.

It would be useful to find a blend mode in Photoshop that is equivalent to this, so I could get an idea of what it would look like.
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Resource contributor
I am afraid you will find the simulator is excellent at simulating most aspects of flight, but not so well the nuances between thick overcast and twilight. For one thing, the algorithm that controls day/night blending, has no input or differentiation from the weather engine. Time of day is the only metric for ambient light.
I found out now that Photoshop's soft light blend option gives an approximate representation of the blending that takes place in P3D, with the standard texture on the top layer and the LM texture on the layer under it. Also, by making the LM texture black and white (or parts of it black and white), you can neutralise the blending effect to some extent. I've managed to create the effect I wanted, almost.