Planetary rings with image textures

Hi everybody,

I did a number of Google searches and searches here at the forum to find info on this question and discovered many tutorials… all with broken links from 4+ years ago.

I have color and transparency texture images that I would like to map onto a disk to represent planetary rings (a la Saturn). Each image is 915x1 pixel map with either color or alpha values. I have tried just about all the possible combinations of the projections (UV, Orco, Flat, Cube, Tube, Sphere, combinations of XYZ, etc.) over the last 3 hours and I don’t get anything remotely resembling a circular set of rings.

Does anyone have a newer tut they can point me to? Or just give me a step-by-step for achieving this effect? Is it easier to map the texture onto a circular plane with a hole in the middle, or map the texture to a bar and warp or extrude the bar around the planet? I am going for accuracy here, otherwise I’d just get the effect with a procedural… although I still wouldn’t get the rings to wrap around the planet. :mad:

Thanks in advance

You might try taking your 1x915 image into the gimp or photoshop, and changing its size to 915x915. This should have the effect of spreading the pixel value across the whole image. You can then model the rings as an extruded and scaled out circle, then UV map the rings to the spread out image.

Hi Orinoco,

Thanks for the suggestion about UV mapping. I’m lousy at it, so I hoped to avoid that method. But I refreshed my memory with Greybeard’s video tutorial and jumped in.

I tried putting one seam in the ring (extruded & scaled circle), and did a map. I got a smooth, smiley-shaped curve composed of quads. I can load the square image that you suggested making and I get colors to map to the ring. But no matter how I try to pin vertices, I can’t get all the quads to be rectangular AND connected in a continuous row. When I select “Quads Constrained Rectangular” I do get rectangles, but they overlap and still form a smiley-shape.

Specifically, I’d like to get the inner ring of vertices to lie at the top of the image and the outer ring of vertices to lie at the bottom of the image. Otherwise, the UV mapping will produce oval-shaped bands of color instead of circular rings. Is there a way to force vertices into this shape without selecting and dragging every one?

[EDIT: A ha! I found under the “w” menu an “align y” command. That snapped all the top vertices into a line, that I dragged to the top of the image. Ditto for the bottom vertices.]

OK, I spent some time messing with the color image (png) and the transparency image (gif) using the UV map I made for the rings. The UV coordinates were found using the color image. Both the png and the gif are 915x915 as Orinoco suggested.

The color is properly mapped as circular bands centered on the ring. But I cannot seem to get transparency to do anything. The only success I had was making the entire ring transparent (alpha=0). Oddly enough, it still cast a fully dark shadow.

I don’t have much experience with transparency (something I want to improve), so any advice would be very welcome!

I’ve posted my ring test file to my website:

Thanks in advance.

Yup. One thing we all learn about UV mapping is the automatic unwrapping only gets close – there’s always some tweaking to do afterwards. Fortunately, Blender’s tweaking tools are getting better and better.

Info on transparency.

Orinoco: I’ve seen that page many times, but it never made sense until now.

By controlling the DVar and/or A value for the material, in combination with the texture produces the correct result! I now understand that the texture is acting in addition to the alpha value set by the DVar and A values together.

Once I’ve got images ready, I’ll post them in the WIPs forum.

Thanks for your help!