It is currently Mon, 29-05-17, 15:19 GMT

All times are UTC




Post new topic Reply to topic  [ 1 post ] 
Author Message
PostPosted: Thu, 02-07-15, 5:23 GMT 
Offline
User avatar

Joined: Tue, 04-09-07, 21:55 GMT
Posts: 749
Location: N 42.38846 W 83.45456
An example of the workflow for converting the data in the scientific archives into something that can be used here in celestia.sci

first thing is there is really NO one and only one standard for data
a shapefile in .tab format can be one of MANY DIFFERENT types
so READ!!! the accompanying *.lbl file

for this one
http://sbn.psi.edu/pds/resource/bennushape.html
--data--
http://sbn.psi.edu/pds/asteroid/EAR_A_I ... V1_0/data/

the "101955bennu.tab" is in fact a vertex mesh and is basically identical to the Wavefront "obj" format

this data set also has a VERY NICE pdf of the ORIENTATION!!!
--- PDF-- just a single image
http://sbn.psi.edu/pds/asteroid/EAR_A_I ... /bennu.pdf

on to the workflow i use
# 1
read then REREAD documentation

then go over it again - it is VERY easy to mix up the orientation of the mesh in Blenders 3d space
( blender and 3d studio max USE DIFFERENT !!!! direction x,y,z for UP )

in THIS case copy the tab file to a new name with the suffix of .obj
and open in blender and ROTATE "X" by -90 degrees
-- Bennu quad view in Blender
Image

as was brought up on the Vesta thread
viewtopic.php?f=4&t=682&p=13283#p12504
that is a simple cylindrical DEM of the asteroid and not a "shapefile"
Image


i tend to add extra detail to very low res meshes
For that process i need a DEM from the above bennu mesh

This is not a tutorial on "Baking" a displacement map in blender
see:
http://blenderartists.org/forum/index.php
and youtube for that

One can be made
-- 8 bit normalized ( 1,255) copy of the 32 bit floating point image
Image


for adding details , basically "shopping" there are no real rules so for this
so for this

Original image ---> "image processing Magick" -- = output image ( see image below )
-- 8 bit normalized ( 1,255) copy of the 32 bit floating point image
Image

so now we have a plate DEM like the DEM in the Vesta archive
and the OLD'ish tab files in the "shape model" thread
viewtopic.php?f=4&t=636

-- This is for BLENDER ONLY !!! --
there is a plugin for importing the MOLA and LOLA pds DEM's
http://wiki.blender.org/index.php/Exten ... G_Importer

and see the blender artists forum page on this plugin
http://blenderartists.org/forum/showthr ... 1-06-25%29

the pds .img files are really just a RAW image with a detached header
and they are in 16 bit SIGNED !!! format

For the above dem in this guide ( i use 32 bit float to work on images ) it needs to be converted to ( " short " "16 signed" )
( the pixel values are in CENTIMETERS seeing as this rock is only 260 Meter in radius )
min value of 22907.1
max value of 28571.3

subtract the MEAN value ( "sea level" ) this gives you a image with positive and negative values
save it a a 16 bit SIGNED raw image
then rename "raw" to "img"

a header is also needed
meshes are BIG -- HUGELY BIG
this lbl is for a 4 ppd .img
-- save as matching name.lbl (4ppd.lbl & 4ppd.img )
Code:
PDS_VERSION_ID            = "PDS3"

TARGET_NAME               = MOON


OBJECT                    = UNCOMPRESSED_FILE



  OBJECT                  = IMAGE
   
    LINES                 = 721
    LINE_SAMPLES          = 1440
    SAMPLE_TYPE           = LSB_INTEGER
    SAMPLE_BITS           = 16
    UNIT                  = METER
    SCALING_FACTOR        = 1.0
    OFFSET                = 24627


  END_OBJECT              = IMAGE
END_OBJECT                = UNCOMPRESSED_FILE
OBJECT                    = IMAGE_MAP_PROJECTION

 MAP_PROJECTION_TYPE          = "SIMPLE CYLINDRICAL"
 MAP_RESOLUTION               = 4 <pix/deg>
 A_AXIS_RADIUS                = 1 <km>
 B_AXIS_RADIUS                = 1 <km>
 C_AXIS_RADIUS                = 1 <km>
 MAXIMUM_LATITUDE             = 90.125 <deg>
 MINIMUM_LATITUDE             = -90.125 <deg>
 WESTERNMOST_LONGITUDE        = -180.125 <deg>
 EASTERNMOST_LONGITUDE        = 180.125 <deg>

END_OBJECT                    = IMAGE_MAP_PROJECTION

END


fairly self explanatory
lat / long start at the CENTER of pixels
" OFFSET = 24627"
is the MEAN value YOU SUBTRACTED from the 32 bit float ( or the pds set offset -- this is sea level)
Lines needs to be an ODD VALUE!!!

and import
see the blender artists forum page on this plugin
http://blenderartists.org/forum/showthr ... 1-06-25%29

quad view of the augmented dem
Image

using Blenders remesh( 9 octaves is my default) tool to remove the polar pinch from using a UV sphere
a 4 ppd image ( 2 meg) is a 58 meg obj mesh

the end result is something like this
Image

_________________
"I don't pitch Linux to my friends, I let Microsoft do that for me."
Using OpenSUSE 42.1 & Scientific Linux 6.7


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 1 post ] 

All times are UTC


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
cron
Powered by phpBB® Forum Software © phpBB Group