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The Moon [message #68013] Tue, 14 May 2013 21:49 UTC Go to next message
avatar bvr  is currently offline bvr
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Registered: November 2010
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Junior Member
I'm hoping someone might have some insight on this.
I downloaded the color relief shaded DEMs for the moon. I managed to get an acceptable sphere from the images, I may go back and try it again hoping for better results.
Then I had a go at remapping the color shading to b/w, this definitely needs more work.

Now for the good stuff,
The spherical elevation map in color weighed in at 500MB, I converted it to b/w and down-sampled it to 6MB.(4000x2000px)
I'm using Blender 2.6
I'm using a 100mm sphere for the model.
In order to get the details from the map I ended up with 5.6 million faces. It isn't working so well with my whopping 2GB of ram...imagine that!.
Is there another way to get the detail from the map with out having so many faces?

ps. Anyone know which way is up?

Re: The Moon [message #68036 is a reply to message #68013 ] Wed, 15 May 2013 06:46 UTC Go to previous messageGo to next message
avatar AmLachDesigns  is currently offline AmLachDesigns
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Registered: September 2011
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Looks good so far...

In Blender, to reduce the polygon count the Modifier to use is Decimate. This should by preference remove triangles that do not contribute to the topology so much.

However, there is a limit on files for SW of 1 million triangles (not polygons), so you would have to remove more than 80% of your faces assuming they are triangles and more if they are quads or other polygons. Plus if you are having problems with the size of file on your computer, this Decimation could take quite some time, assuming that Blender does not crash anyway.

I should mention also that there is a max size of 64M for file uploads to SW.

Is your sphere hollow? If not, that will be quite an expensive object. But hollowing will add triangles.

How many triangles in your basic sphere? How is the lunar topology added to that sphere? Investigating these 2 factors may help.

Like I say it looks good so far, I hope some of the above will help you get a printable model.

And no, I don't know which way is up!

Good luck...
Re: The Moon [message #68039 is a reply to message #68013 ] Wed, 15 May 2013 07:14 UTC Go to previous messageGo to next message
avatar mkroeker  is currently offline mkroeker
Messages: 3700
Registered: June 2012
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Shapie Expert
How much does it degrade when you decimate the mesh, or when you downsample the map further
before creating the spherical mesh ?
Both should hopefully remove the smallest features first. (And you could try printing it in FCS with the
texture-mapped image to visually recover the finer details). Definitely make it hollow, with the escape hole
on one of the poles or in one of the biggest craters - back of the envelope calculation gives ~520cm3 for a
solid 100mm sphere, and only ~60 for a hollow one with 2mm walls ($390 vs $45 in FCS, $1800 vs $210 in FUD).
Re: The Moon [message #68179 is a reply to message #68013 ] Thu, 16 May 2013 22:54 UTC Go to previous message
avatar bvr  is currently offline bvr
Messages: 0
Registered: November 2010
Go to my shop
Junior Member
I have not tried the decimate modifier, I was not aware that it only removed from non "busy" areas. I will give that a try.
The sphere is hollow now. The wall thickness is 4mm for now, only because I didn't know how deep some of the craters were.

I am aware of the limits for file size and face count, that's kinda why I was inquiring.
I still need to nail some of the basics tho... I'm not even sure I have the displacement map "normal" facing the correct way-and I still am not sure which way is up. The image work takes some time due to file size, so i was trying to get a better handle on the blender steps before I commit to full size. I'm wondering if there is some way to average the data. I know at some point there is no reason to use a smaller face(more faces total) because you will already be exceeding the printers resolution.

My basic sphere is around 25k faces(then subdivided) and I'm using a grayscale image with the displacement modifier to create the topology. The conversion from color to grayscale is somewhat iffy too. photoshop only remaps in color steps( 6 sliders) so I set 50% gray to approx. 0ft elevation(which is not necessarily correct) and try to get an even blend around it.

I'll let you know what happens with the decimate modifier. I was planning on FCS. I had considered using the displacement map as an image texture. I think I'd rather have less detail and no image on it...if i can get there from here.

Thanks for the input both of you.

ps: Shapeways, if you're listening, and have considered printing in cheese...this would be a great thing to print in cheese. Laughing just sayin'

[Updated on: Thu, 16 May 2013 22:54 UTC]

Buffalo, 360° @ a time

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