Sky Dome Texturing

[Neison]

Yes, it's warped perspective so that it doesn't stretch. Perhaps take one of the skydome photo examples, determine perspective lines and draw out a grid and paint within those guides.

[Childe]

Is this how everyone else does it?

What about when i use photos? And painting a nice sky like that will be difficult...

[Sassafras]

Stretching can be prevented by modifying the UVs, but i'm not sure if this is the answer to your questions since you didn't quite specify what part of your results you're not happy with.

With the UVs tweaked your circular texture looks fine to me.

[Childe]

Hmmm, i see...

I guess its time i really find out how to use UV's properly lolz.

Thanks!

[EricChadwick]

I photographed some skyboxes recently, worked out great. Some tips further down in this thread...
http://boards.polycount.net/showflat.php?Cat=0&Number=165550&an=0&page=2&vc=1

Here's a scaled-down sample, in latlong format (easy to convert to a cubemap).
http://www.ericchadwick.com/examples/images/2006.12.28_squallpassing_latlong.jpg

[Logan779]

I think I may be able to shed a little light on this, I too have had problems with texturing Skies.

Your problem is most probably to do with the Mesh (modelled dome) that the sky fits on. Now finding out where the apex sits and joins is an endless case of tweaking.

What I would suggest is replacing and or investigating the Mesh (ask one of your model team to look at where it pinches and remodel it) OR paint a grid system you can refer too to isolate the pinch area and then allow enough room in your painting to free that area up.

[EricChadwick]

If you need to paint the sky, either use 3D paint (Body Paint 3D is currently the best IMHO), or use SkyPaint.. this program allows you to paint directly into a cubemap... http://www.skypaint.com/

[Childe]

Thanks Eric,

Both links were very useful :)

[Marcel]

If you need to create a cubemap then you can create a hemisphere and texture the sky in the way that is most easy for you. When the sky is done, you simply add 6 camera's that render our images for top, bottom, front, back, etc...

If you use Max then there is a special function to render our cubemaps. I think it is hidden somewhere in the reflection map node in the material editor, you pick and object and it renders out 6 maps from that viewpoint.
When the end result is a .DDS cubemap texture you have to place them in a special order and save it out in Photoshop. Let me know if this is the case and I will look it up for you.

[stuh505]

There is another, very general, way to do this.

Create a cube with 10 subdivisions on each side. Do a box UVW map, then stitch together the faces into the cube configuration.

Then apply a spherify 100% modifier. Then apply a UVW unwrap modifier, select all the faces, and remap them on channel 2 using a spherical map.

Then apply a spherical texture map to it. It will use the most recent channel 2 spherical uvw coords.

Then do Render to Texture. Add a diffuse map. It will render the current texture into the UVW coords of the first channel (a cubemap).

Create a skylight, and then render. The skylight will give uniform ambient lighting equivalent to disabling lighting.

This will produce a perfect cube map for you...and you can use this to produce much more specialized maps, as well.

In my game right now I am testing out using other types of environment maps...I'm using a geosphere with zero distortions, packing all the triangles into the map..then painting a texture over the surface in Deep Paint, so there will be no distortions and no seems anywhere.

[EricChadwick]

The DDS-cube renderer in Max is piss-poor IMHO, it's limited to just 256x resolution. Material Editor, Standard material, DirectX Mgr rollout, Enable Plugin Material, change to Metal Bump9, down at the bottom click "Pick object and create", click on an object.

I use the NVIDIA Photoshop plugin to make DDS cubes instead ( latest version (http://boards.polycount.net/showflat.php?Number=115830), older version (http://developer.nvidia.com/object/photoshop_dds_plugins.html)), just packing my six bitmaps horizontally into a single image, then saving. The layout it expects is +x, -x, +y, -y, +z, -z.

+X = _RT.tga
-X = _LF.tga
+Y = _UP.tga
-Y = _DN.tga
+Z = _BK.tga
-Z = _FR.tga

NVIDIA also has a Script for Photoshop called Cube Map Shuffler (http://developer.nvidia.com/object/photoshop_dds_plugins.html). It'll auto-convert a horizontal +x-x+y-y+z-z image into a cube-cross layout.

ATI's CubeMapGen (http://ati.amd.com/developer/cubemapgen/index.html) is another helpful utility, easily converts between different cubemap layouts, also lets you sample them down to make soft-reflect or diffuse-lighting cubes. Pretty cool.

How to use 3ds Max to render a six-bitmap cube:
Set up the Renderer how you like it. Open the Material Editor. Add a Reflect/Refract map anywhere. Change radio button to From File. Change the spinner to the resolution you want. Click the bottom-most blank button, specify a filename prefix and the format. Click on the "Pick object to render from" button, click on an object to render from its POV.

stuh505, sounds like a lot of work. If you want to convert a spherical-projected map into a cube-cross layout cubemap, it might be easier/faster to put it in the Environment Map slot (be sure to change to Spherical projection), render from a Reflect/Refract map, then use ATI's or NVIDIA's tool to combine into a cube-cross.


I hope this helps, took me awhile to figure all this stuff out. Seems like there's always a bunch of tools one has to use just to get a particular effect. :)

[jgray]

I'm no master at Sky Domes, but I have spent a lot of time trying to develop them. Try these tips and let me know what you think.

First, the attached ZIP contains 7 Sky Dome images that I developed years ago (edit: try this LINK (ftp://ftp.g3d.net/g3D_SkyDomes.zip)). They were taken with a fish-eye lens, the same one used for iPix panoramas. They are only 1K images but you are welcome to use them as-is, or as a template. To avoid the stretching problem, do the following (assuming you are using MAX):

01. Create your dome
02. Apply the Sky as a material
03. Apply a UVW Map - Planar
04. Apply an Unrwap UVW and select EDIT
05. Select all verts, then select the menu item Tools/Relax...
06. Relax Tool parameters:
- Relax by Centers
- Iterations = 1--
- CHECK Keep Boundary Points Fixed
- CHECK Save Outer Corners
07. Click APPLY a few times...

Another resource I've used is a program called Texture Maker ($75 as I recall). Beyond being able to produce cool, seamless textures, it also has an easy to use, yet effective sky generator. It would get you most of the way there, but I would recommend you do some detailing in Photoshop after the fact. The sky textures are rendered for cylindrical mapping.

Good luck.

Joel

[Childe]

I use Maya :P

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