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Controlling Mipmaps

G

gadgets

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In my airport sceneries, I tend to make extensive use of SAMM-generated static aircraft. Since my scenery textures are mipmipped, I use mip-mapped textures for the static aircraft as well. But, very often, the first mipmap is activated when only a few feet from the aircraft, and logos, etc. start to get blurry.

There are lots of posts on this sort of problem. Most end the same way, i.e., with Arno asking "Have you checked the texture scale?" or offering something along the lines of "MakeMDL has a bug that affects texture scale causing mipmaps to activate too soon" or "let MDL Tweaker change the texture scale" - but nothing definitive.

I don't want to have to tell SAMM users to submit their static models to MDL Tweaker. What would be very helpful is if Arno would provide an explanation of the problem and how the texture scale should be adjusted to prolong display at full resolution. Once I know what to do, I can quickly update SAMM - assuming there is a way to do it and Arno doesn't regard the fix as a trade secret.

Please, Arno:confused:

Don
 
Hi Don,

Are you talking about FS2004 models here? In that case it could be the texture scale indeed.

In the texturelist command one of the parameters of each texture is its scale. So how many meters the texture covers. Makemdl sometimes calculates this scale wrong and that affects mipmap selection.
 
Hmmmm.

An similar entry for FSX models, Arno ....

or is it simply minimum or maximum texel density that determines Mip switching?
 
Are you talking about FS2004 models here? In that case it could be the texture scale indeed.

In the texturelist command one of the parameters of each texture is its scale. So how many meters the texture covers. Makemdl sometimes calculates this scale wrong and that affects mipmap selection.
Click to expand...
FS2004 models are my concern at the moment.

What I'd really like to know is what change SAMM would have to make to that value to delay mipmaps becomong effective. I've tried doubling the value, for instance, and it doesn't seem to make any difference

If you don't mind disclosing a "trade secret", what does MDL Tweaker do to detect an incorrect scale and how does it fix it.

Don
 
Hi,

hcornea said:
Hmmmm.

An similar entry for FSX models, Arno ....

or is it simply minimum or maximum texel density that determines Mip switching?
Click to expand...

There is no texture scale defined in the FSX models anymore. So I think it is indeed the texel density that matters. So in other words, give all areas of the texture the same resolution.
 
Hi Don,

gadgets said:
What I'd really like to know is what change SAMM would have to make to that value to delay mipmaps becomong effective. I've tried doubling the value, for instance, and it doesn't seem to make any difference

If you don't mind disclosing a "trade secret", what does MDL Tweaker do to detect an incorrect scale and how does it fix it.
Click to expand...

What MDL Tweaker does is to check all triangles and based on the UV coordinates calculate what the texture scale would be (amount of meters that the texture would cover at that mapping). It then takes the biggest value, since that would trigger the mipmap changes quickest.
 
Thanks, Arno. I now understand (I think) what you mean by "checking the texture scale" and what the end result should be.

To summarize, I understand FS expects the texture size to reflect the distance represented by the model that would be covered by the largest dimension of the texture sheet. From my experiments, larger is better than smaller (i.e., if the texture size is very small, the first mipmap cuts-in too early). So, if portions of the texture are used at different UVW scales, the texture size in the .mdl file should reflect the largest distance covered by the texture.

I don't plan to examine evey triangle in SAMM. However, aircraft textures (the ones of most interest) generally cover the length of the aircraft, half the length, etc.. So, if there are problems, in addition to the ability to edit individual texture sizes, I'm going to give the user the ability to globally change all texture sizes to the radius of the aircraft, 1/2 the radius, etc.

Does this seem reasonable?

Thanks again for the help.
Don
 
Hi Don,

Sorry for the late reply, I was away from my work for a couple of days.

The problem mainly occurs when there are different resolutions on the same texture sheet. So one triangles use a part of the texture at a different resolution then others. If all triangles use the same scale, the value is calculated correctly by MakeMDL.

The texture scale is related to the size of the texture sheet, not only the part that is used on your model. So even if you only use a small part, the scale will reflect the size of the full texture sheet.

I guess for aircraft the estimation you give could work. Although I can also imagine that small details like landing gears, etc can have a different mapping.
 
The texture scale is related to the size of the texture sheet, not only the part that is used on your model. So even if you only use a small part, the scale will reflect the size of the full texture sheet.
Click to expand...
That's what I was trying to say, so there is no misunderstanding.

I guess for aircraft the estimation you give could work. Although I can also imagine that small details like landing gears, etc can have a different mapping.
Click to expand...
SAMM's texture editor allows texture size to be specified on a texture-by-texture basis. The way I implemented the change, the x1, x2, etc simply presets a textbox which the user can either accept or change to any value he/she wants.

Thanks for the advice,
Don
 
Hi Don,

Sounds good, I think that should work.
 
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