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What is the maximum/preferred image resolution for using images as materials

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I recently created a helipad and because the ground markings at the real helipad are quite unique, I created an image from Google Earth downloading it at the maximum resolution thinking that it would result it the best image displayed in MSFS. I applied that image as the material for a plane in Blender. This has increased the size of my package greatly and I'm not sure if it has resulted in a better image in MSFS than using a lower resolution image for the material.
The resolution from Google Earth is 5180 x 4816 and is for a ground area of about 60 meters x 40 meters.

I read elsewhere in this forum that not saving with alpha channel set reduces file size however the difference was 11MB to 10Mb hardly worth considering. Also to save as a 16 bit (png) image however my image editor only seems to allow 24 bit.

What maximum image resolution should I use so that I don't loose any MSFS resolution? All texture images I have seen for downloading are no more than about 2024 x 2048 however they appear to cover an area of maybe only 1 meter x 1 meter.
Would using a .jpg instead of a .png result in a smaller package?

helipad_transparencies.jpg
 
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The big question is are you putting this in the sim as mesh (FSX/P3D ground poly style) or using it as a projected mesh?

Rule of thumb is to use as small of a texture as you can get away with. As someone who has crossed that bridge in the past, I would never go any larger than 4K. I find myself trying to figure out how to make things in 2K more now. And if you are doing it as a projected mesh, you may not need more than that.

My approach to this would be to use 1K tiling textures as your base layer and all of the paint using decal material and overlaid mesh. Use a handful of small textures vs one large texture. Or you could paint the entire base mesh in 2K, use that aerial image, cleaned up, as a bit of a grunge overlay and then use a detail texture on top of that for a more fine asphalt/concrete texture. Then decal and mesh for the paint.

A bit more effort than painting it all as one, but you'll use a fraction of the texture memory and keep a pretty high resolution. Much higher than the aerial image alone.

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Clarifying a few more of your statements:
  • Removing Alpha channel is recommended if you are not using it. It's a whole other channel, so it will double your compiled DDS file size.
  • Image format does not affect DDS output size. Always use PNG when able. TIF is a good fallback. I prefer it when working with Alpha channels. JPG is lossy and shouldn't be used if it can be avoided. I'm not sure that the sim will even compile it...
  • Source file bit depth makes no difference in DDS output size. Just the quality it starts compressing from. The sim chooses what bit depth to compile at for each texture slot. Rule of thumb is to use 16-bit when possible:
If you right click on an image and do Properties > Details in Windows, it will show you the total bit depth of all channels, so:
24 = 8-bit
32 = 8-bit + alpha
48 = 16-bit
64 = 16-bit + alpha

It sounds like you photo editor uses the left column for bit depth, so you can find the correct translation on the right. As you mentioned 24-bit in your text above, that would actually be 8-bit (8 bits per channel x3 for R-G-B).
 
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The big question is are you putting this in the sim as mesh (FSX/P3D ground poly style) or using it as a projected mesh?
Thanks for your detailed response.
No not using as a projected mesh.

My approach to this would be to use 1K tiling textures as your base layer and all of the paint using decal material and overlaid mesh. Use a handful of small textures vs one large texture. Or you could paint the entire base mesh in 2K, use that aerial image, cleaned up, as a bit of a grunge overlay and then use a detail texture on top of that for a more fine asphalt/concrete texture. Then decal and mesh for the paint.
Wow that seems complicated for my ageing brain.

Thanks for the tip re .png preferred.

Since posting I have tried a few things and noticed that if I reduce the number of colors then the output .png file reduces quite a lot yet the appearance (of the image itself) seems much the same. Not sure if that would flow onto the compiled dds file size.

I reduced the resolution (less pixels) but the image quality suffered a lot.

I will remove the alpha channel as I only included it so that transparent area around the edges (seen in image above) would not show but since then I have found I can use the knife took around the periphery of the helipad image to remove the transparent areas and so don't require the alpha channel to be included.

Thanks again.
 
Since posting I have tried a few things and noticed that if I reduce the number of colors then the output .png file reduces quite a lot yet the appearance (of the image itself) seems much the same. Not sure if that would flow onto the compiled dds file size.
You will only see that difference in the PNG size. It makes no difference in size when it's compiled to DDS. You might as well leave it be.

Yeah. The tiling stuff and using the different layers can be a little complex. There is definitely a bit of a learning curve. I'm only just starting to get the hang of it after a lot of playing around with what does and doesn't work.

If you don't want to go that far, you can probably get away with using a 4K texture. I would redo it from your 5180 x 4816 source though and fill up as much of that transparent space in the texture as you can. Utilize that texture space for more resolution.
 
The goal is going to the lowest resolution without sacrificing detail. What I know about your project is that you could probably use 1024 x 1024, without alpha. I was thinking of using JPG and compressing, but it seems there is no advantage as the compiler will make the resulting .jpg.dds the same size as the .png,dds
 
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Thanks Dick
I have now turned off alpha however even reducing resolution even slightly appears (in my image editor) to greatly affect detail. Remember the image I have is from an area of about 60 meters (wide) x 40 meters.
I have just reduced the resolution to 2048 and didn't much difference to the detail so will try 1024. I guess halving the resolution to 2048 and not including the alpha channel more than halved the png filesize.

I also wonder what a typical resolution Google Earth satellite images is.

I decided to do a comparison by zooming in to just the perimeter of the asphalt area of the helipad I then saved at the 4 selectable (Google Earth) resolutions (1396x822 through to 8192x4230), then opened each one in Paintshop Pro, zoomed in to just the marking of the circle for the helipad and could not see any difference in detail between them all and as such it seems IMHO that I should use the lowest resolution image and save a lot of space or wouldn't the difference in size of the compile DDS file be much different I wonder. Time to check that out.
 
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Now better. My package has reduced in size by around 30Mb and the .DDS file is now only 537Kb instead of 31.7Mb and still 'looks' ok in MSFS.
 
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