Geo referenced Files

[mash]

Hi, I'm tinkering around with the Geo referenced files and shaders.
I download 1/3rd arc second Mt.St Helens and ortho imagery from the national map viewer.

The files load up ok and the sat images are in the right place.
The only problem I'm having in the bounding box for the Dem data is at an angle to the planet.
This seems to be making rotating around the DEM to the left or right a bit difficult.
Instead of orbiting the target the camera keeps wanting to rotate around it's own axis to the left or right.
I can get around it I was just wondering if I missed something.

In the You tube demo Oshyan did I noticed he set the planet Lat long At apex to 90.
Is that still a necessary step?

Also any idea on what do to fixed the washed out colors of the Sat Images?
I futzed with the Data is linear and tried gamma at .4546 but that didn't work.
Thanks.

[Oshyan]

Changing the Lat/Long At Apex is still a good idea. You could try a Colour Adjust to fix the "washed out" look, possibly?

- Oshyan

[mash]

I added a color adjust and that helped with the washed part out on the downloaded satellite images.
Is there any way to add a geo referenced image file that does not go through Geog image map shader?  I'm under the impression that the geog image shader is set up to read just gray scale satellite images with embedded color bands.
I have a image that I geo referenced through Global mapper.
When I run that image through the geog image shader the colors get blown out and no amount of color correction will fix it.
Thanks,
[attachimg=1]
[attachimg=2]
[attachimg=3]

[Oshyan]

The Geog Image Shader is the only way to *georeference* a loaded image. I'm not certain but I would think it should support various import data. I hesitate to say your output from GlobalMapper was "not ideally formatted", but you might look and see if you can adjust it there... There may also be remaining options for color correction in TG, though I'm not sure what you've tried.

- Oshyan

[mash]

I went back and checked global  mapper and I also saved the image as a Jpeg2000 and brought that in with the same results.
I noticed in the Geog shader under the color tab there is an option for "Convert to Linear" or "Data is Linear"
If I turn on Multiply RGB and set all the numbers to 0.45 0.45 0.45 and have the color adjust shader turned on with a gamma of .4546 it looks almost correct.
So I think I'm making a mistake in how to work a with a non-linear image in Tg3.

In other programs like Modo or Maya to get a non-linear image to work in a linear workflow the imported images need to their gamma set to .4546, other wise the image looks washed out.
What is the proper workflow to work with non-linear images in Tg3?

[jo]

Hi,

When I was writing the Geog image map shader I used data from Mt St Helens for testing. It didn't strike me as being blown out using the default settings, although it certainly does if you check the "Data is linear" option in the Colour tab. However it is rather bright compared with the display in the National Map viewer. OTOH the National Map isn't rendering with sunlight and atmosphere etc. It didn't strike me as being particularly wrong. It may be that you need to adjust the colours with images from various sources to get a pleasing result. However I will look into this some more.

I don't know how Modo and Maya are handling gamma, but it seems like what you are doing with the 0.4546 value is actually doing the opposite of what TG is doing. However looking at the docs for Modo the intention is to convert to linear:

http://docs.luxology.com/modo/601/help/pages/shaderendering/ShaderItems/ImageMap.html?zoom_highlight=gamma

So it's doing the same as TG but in a slightly different way.

Using the Multiply RGB parameter won't give you the correct results because the gamma encoding/correction is a power function rather than a straight multiplication. It might give you results that you prefer but it's not to do with gamma.

The proper workflow for non-linear images in TG should be to simply let the shader do the conversion to linear. Obviously this works best if you know the image gamma so you can use the correct value if it's not 2.2, but 2.2 is pretty typical.

The Image map shader and Geog image map shader use exactly the same code to render the image. The main difference is that the Geog image map shader can georeference the image. If you loaded a GeoTIFF into a Image map shader and a Geog image map shader it would render the same AFAIK.

I'm under the impression that the geog image shader is set up to read just gray scale satellite images with embedded color bands.

I'm not really sure what you mean by that. The shader looks in the file for the available data and loads it appropriately. You can see how an image's colour data is interpreted by looking at the information in the Info tab. For example it loads the National Map orthoimages as RGBA. The images are colour and TG is reading that colour information.

Regards,

Jo

[Matt]

It might also be a matter of TG's default sunlight brightness, which is 5. Any image which is brought into Terragen and lit by sunlight with intensity 5 will render brighter than the original image. Some satellite images might be exposed to a level that renders too brightly in these lighting conditions, i.e. white pixels don't represent 100% albedo, they represent something darker. Even if they are exposed correctly, you might find TG's default lighting is too bright to render them nicely. You might choose to darken the image or adjust the lighting in Terragen. Neither way is necessarily "wrong", but it depends on your goals with regard to physically correct lighting among other things.

Matt