Spherical wrapping a planet....... with very large images !!!

Started by pclavett, September 05, 2020, 01:46:57 pm

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pclavett

Hi guys !
I was doing a space scene and put my camera on the Himalayas and rendered the image below.
Now the image used was gigantic. It was an earth spherical planetary map that was 65,536 px wide by 32768 in height. It was an assembly of 2048 tiles obtained from the Celestia website. Took me about 2 days to put it together in Photoshop about 2 years ago. The file was 1.6GB as tiff and 1 px above the maximum for turning into a JPG ! Brought it down to 65,000 x 32500 and made a JPG that was about 125 MB. Eventually made a variety of versions of different sizes because of wrapping issues. 65,000 px would not wrap at all. 60,000 appeared OK for the image that I was doing and the render below was with that image. Rendered at 10,000 px gave great definition of the texture and the detail was amazing, in line with the fantastic detail in theses images.
When I repositioned the camera though........ a wrapping issue was evident. Changing the size of the image was done to experiment with this and finally determined that proper wrapping started to deteriorate at 55,000 px.
All the images used are of the same pattern and are 2:1 in dimension.
There appeared to be a valid wrapping with a nominal image found on the web at 10,000 px. 60,000 px showed a huge polar artifact. At 55,000 px the polar artifact appeared gone but note the colour artifacts showing a circle pattern. At 53,000 px, there seemed to be no issue, at least with this small render and distance. The setting for the Image shader were always the same for the different trials.
There may be a software limit preventing such sizable images from being handled properly but Matt et al. will be able to enlighten us on this.
Note however that this limit means little as the details obtained with the 53,000 px image are more than adequate. I have also included a small sample of the detail in the 53,000 px image and a render (no atmo to haze the texture) of the same general area on the planet at 10,000 px and maxed quality so you can compare the level of detail. The render was brought down to 700 pixels for comparison with the section of the image taken. When you examine the two images at "actual" pixel depth (100%)...... the detail seems to be relatively similar ! Quite close in my humble opinion ! Some of the colour and highlights will be affected my light and other tonemap adjustment ! Enough detail to make a great poster !
I wonder if others have had this issue and must say I did not do a search ! Mind you, using this size image will not be needed very often. The renders with the 53,000 px image were definitely better than the ones I did with 20,000 px..... not included here.
I wish all of you a great weekend !
Paul

KyL

I remember using 53k as a sweet spot for high res textures too as it seem to break above that.

Using several smaller images is also more efficient as you can simply load the tiles visible in your field of view.

WAS

Quote from: KyL on September 07, 2020, 08:08:47 pmI remember using 53k as a sweet spot for high res textures too as it seem to break above that.

Using several smaller images is also more efficient as you can simply load the tiles visible in your field of view.

How do you spherically wrap tiles? That is processing wise, I imagine in TG it's just rotation? Though could be wrong.

On that note, does someone know how to properly take a super big orthographic texture and sphericalize it for use in TG? I couldn't really find anything on this when I searched awhile back.

KyL

Quote from: WAS on September 07, 2020, 09:14:51 pmHow do you spherically wrap tiles?
I use geog image map shaders and manually enter longitude and latitude for each tile.

But usually for the earth the files are correctly georeferenced anyway.

pclavett

For making a spherical adaptation this may be useful if you plan on creating planetary images that can then be applied spherically !
http://multimedia.uqam.ca/Animate/Expe%CC%81rimentations%20Belzile/Make%20a%20Spherical%20Map.pdf
PDF file itself below !
It usually helps when the polar area are more uniform in texture for the artifact corrections.
Hope this helps !
Paul

pclavett