3d scan of imperfect globe to a 2d Equirectangular Projection

[Vigilus]

This is for the 3d Vaeya globe project I have in the world mapping section of these forums.

I'm using blender.

Just trying to find a way to reshape the UV map in such a way that the 3d globe comes out looking like a regular equirectangular projection.


This picture shows the rough layout of the UV map. As you can see, it's nowhere near an equirectangular projection.

TouchingUp.PNG

I'm working from this imperfect sphere (which was a 3d scan that's been touched up, no mesh work has been done).

Globegame Prototype work.PNG

Here is what the mesh looks like overlaying the UV map

Meshoverlay.JPG

[Vigilus]

That's a lot of views and even more silence from the guild members. I'm at least receiving responses on other websites. I thought this was a place where we help people?

[Greason Wolfe]

Well, what kind of help are you looking for? I, for one, have nothing to offer since I don't use Blender and have no experience with what you are trying to accomplish. There might be others here that can offer something, but if they don't know what you're looking for, it's hard for them to respond in a helpful way.

[Vigilus]

I'm going from a 3d model to a 2d equirectangular projection.

[waldronate]

I am unfamiliar with an 2D Equilateral projection and I don't use Blender. I will guess that you meant "Equirectangular", where the vertical mapping linearly maps the latitude range -90 to +90 degrees to the pixel height of your image and maps the longitude range -180 to +180 degrees to pixel width according to the relation 1/cos(lat) (that is, progressively more stretched toward the poles). In this case, the UV (longitude,latitude) outputs have a simple relationship to things on the globe as described above.

Your first image looks like it has a texture atlas stitched together onto a single image with some external mapping defining the texture-to-sphere coordinates. If you have access to this mapping, you should be able to transform it to points on the sphere and then split up your sphere into some uniform set of triangles and project the pixels from those triangles onto an equirectangular bitmap. In that case, more triangles would give better results, right up to the point where you have triangles that occupy a single pixel in the output image.

Another option would be to take a few images in Blender using an Orthographic projection (view of the sphere from infinity) down each axis of the sphere and then feed them into program that will convert those images into an equirectangular bitmap (I'm partial to ReprojectImage from http://fracterra.com/ReprojectImage.zip mostly because I wrote it and am familiar with it). This sort of thing can be done with many of the common panorama stitchers.

Blender should be able to render cube maps and that cube maps can generally be converted into equirectangular without too much effort. See your local search engine for more information. Your best bet in that case is to put the camera at the center of your sphere, because then the entirety of the generated cube map will be your sphere.

[Vigilus]

Wow Waldronate, that's some serious help, tomorrow will be spent learning these key words and likely a PM or two your direction. Thank you very much!
I've been so frustrated with this problem for just good starting material that I'm starting to look deep into search engines and find a better one than google.
I've discovered a really handy cube map tool specifically for equirectangular projections from a sphere that everyone might like: https://www.youtube.com/watch?v=oklmDQx17HI&t=12s

I've had this annoying habit where I've been substituting equirectangular with equilateral and my brain just can't kick the habit. I've updated the thread with the appropriate terms.

The main issue I'm having at this moment is transposing my imperfect sphere onto a slightly smaller, perfect sphere, so that I can clean up the whole process and start applying algorithms.

Again, Thank you Waldronate!

[waldronate]

Let us know how it works out.

[johnvanvliet]

if the 3d sphere looks good in Meshlab then it will look good in Blender
now the xyz rotation might be off but the is easy to fix


then exporting a equirectangular projection is also rather easy

so first when you view it in blender dose it look fine or all mixed up ?

if it looks fine then all you need to do is "bake" the texture to a second sphere that is UV mapped to a sphere and not UV islands

[Vigilus]

if the 3d sphere looks good in Meshlab then it will look good in Blender
now the xyz rotation might be off but the is easy to fix


then exporting a equirectangular projection is also rather easy

so first when you view it in blender dose it look fine or all mixed up ?

if it looks fine then all you need to do is "bake" the texture to a second sphere that is UV mapped to a sphere and not UV islands

Thanks for your reply johnvanvliet,
To answer your question, the 3d view looks fine, all the UV mapping onto the sphere is spot on and I've done extensive painting using photoshop and 3d painting in blender.

I've done research into baking, yet the videos lack context and an overall process. Without context they don't mean anything practical, it's all academic. I'm hoping to find a lot more context of this process from you guys/gals. Any good baking videos that you link would be appreciated.

To answer your question, if it looks fine then all you need to do is "bake" the texture to a second sphere that is UV mapped to a sphere and not UV islands

Thanks, this is slightly more specific than the replies I've been getting on other websites. Can you go into detail about the process? Maybe a video link or a make a quick video of what you mean precisely?

@waldronate, I will, and I'm still looking into your solutions

Thank you!

[Vigilus]

Also, here's an updated pic where I'm adding more depth to the world by adding in mountainous regions to tie in everything to make the world less "standard game board art style".

Globe Game.PNG

I was hoping to additionally bake the mountain textures into the model as well, trying to preserve the general shading so that I can go extremely detailed later in Photoshop and other programs. I'm trying to preserve the hand painted textured mountains that I scanned off of the original hand painted globe.

Any lighting pointers and techniques on this would be very helpful, also, is it just a normal map bake for that process? If I "bake everything" or "bake all channels" in blender would that be enough? Feel free to correct anything in quotes with better terms.

Thanks!