topographic displays
10 messages in this thread
Hello from behind the learning curve,
I have a project I am trying to complete and have dug myself into a corner.
Basically I need to render a 3d Topography with some freeways and other
utilities displayed on it.
Thru vistapro, and autocad I managed to get the topo. The area is massive,
I had to piece it together from 6 DEM data files (each one is 10 megs ascii)
I have ended up with a topo mesh that is 48,000 faces (it covers a couple
hundred square miles)
Now my problem.
I need to lay objects onto this surface. Take a freeway for example.
The method I used that is causing me problems is:
In autocad I can project plan entities onto a mesh. This gives me a 3d polyline
that I can DXF in as a path in the Lofter and then run a simple quad down it as
a
shape. The problems I have are
1. due to the limitations of autocad the 'freeway' doesn't lay on the topo
nicely
it dives thru or rises above the surface. I have been cleaning up vertex by
vertex, but have rapidly become overwelmed.
2. If I decide the shape I used is to small to render nicely I need to re-Loft
it
and have to go thru the clean up again.
What I would like to do is export the plan view of the 'freeways' to a paint
program and then 'decal' them on to the surface.
Questions:
1. if I scale the plan view down to say '5"x5"' (remember they are currently
in
real world coordinates) will I be able to rescale the decal back up in 3DS
and position it accuratly?
I guess the question is how do you scale and position a decal accurtetly?
2. What size (resolution) do I need to make my decal? I need to be able to
see a freeway from '10 miles' away and when I zoom into it I don't want it
too out of scale. I know I will need to exaggerate somewhat but is there
a direct relationship between pixel width in a file and the scaled width of
a decal? Is it dependent on the size of the texture file.
I guess the optimum would be to create a texture file at the same scale
as the topo mesh
Any suggestions on how to get out the dark alleys I'm in now will be most
appreciated
Todd
Hi Todd,
I think you'd better off going with the texture mapping due to the sheer size
of your model. Moving vertices, one by one, can be a major pain.
When creating the texture map, remember that a high resolution map will
generate a cleaner image. The trade off, however, is that higher resolution
maps will also use more memory during render time. Creating the 5"x5" texture
map could be easily rescaled in 3DS to fit your model.
After you've assigned your bitmap image in the Texture1 Maps slot, save your
new material.
Shift back to the 3D Editor, and use Surface/Material/Choose to pick your
material.
Apply your material to the topo.
Now use Surface/Mapping/Adjust/Align View, and pick your Top viewport.
(You should now see a mapping icon that is green and yellow w/ a little
line off one side)
Using the other Adjust commands, you can scale and move the bitmap to fit your
model.
I hope this helps,
Bob P.
Bob,
Thanks for the info. I started doing this method right after I wrote my
message.
The tough thing I'm doing now is trying to align the 'decal' where I want it
does the lower left corner of the mapping icon define the corner of the
'decal'?
it would seem to be easier to move the icon around rather than fudging with
the 'u' 'v' settings in the materials editor. Correct?
(the first bitmap I made was 18 Megs big…is this typical for 3DS or should I
make a lower res and accept it?)
Todd
Hmmm
Yeah, 18mb is awfully big. The bitmaps I've worked with usually don't exceed
1.5mb.
To create your bitmap, are you loading the model into AutoCAD, looking at it
from a plan view and doing something like a screen capture? If you have
control over the resolution of the capture, I would suggest perhaps 500×500
res. The even resolution will produce a square thus making the placement of
the mapping icon in 3DS much easier.
If you go for an odd resolution like 640×480, use a corner of the mapping icon
as a reference point for helping you place the map on the model.
Moving the icon to position a texture map has always been easiest for me.
Bob P.
I created the bmp by dxfing out the linework in plan view
inporting it into coreldraw and then
exporting as a TGA file.. I only have 3 options on output
600,something
1024×768 = .75 meg file
1 to 1 = 18 meg file
My only problem with positioniing is that I am trying to decal into
a large mesh…the corners of the icon don't relate to anything in the mesh
so its position render position render………
thanks for the help
todd
Okay.
I would first try the 600x??? resolution. If it later proves to be too grainy
or chunky looking, you should then try the 1024×768.
Since you don't have a corner to reference, I think you'll have start by sizing
the mapping icon to encompass the entire model. Then render the model to check
placement. If the map is not correct, shift it around and re-assign the
mapping to the model. (You would not have to re-apply the material each time,
just the mapping.)
For the placement rendering, use a Flat shade mode, and 320×200 resolution.
The image won't look very good, but they'll suffice for testing since they will
render quickly.
Good luck,
Bob
>> I created the bmp by dxfing out the linework in plan view
inporting it into coreldraw and then
exporting as a TGA file.. I only have 3 options on output
600,something
1024×768 = .75 meg file
1 to 1 = 18 meg file
My only problem with positioniing is that I am trying to decal into
a large mesh…the corners of the icon don't relate to anything in the mesh
so its position render position render………
thanks for the help
todd <<
When I export from Corel, I select "custom" size and type in whatever
resolution I need. The is in the Bitmap export dialog (v3) after specifying
the export file name. Note that corel does not antialias and to correct this
you will need to export to a bitmap 200% of your needed size. Then use
Photopaint (or Photoshop or whatever) to resample the bitmap down 50%.
If you end up needing a large map file, you may also want to create a very
small one for your test renders. Then substitute the large file for the final
render. If they have the same proportions, then you canl just swap one for the
other.
Terry Gilbert
Forcade & Associates
>>Using the other Adjust commands, you can scale and move the bitmap to fit
your model.
I hope this helps,
Bob P. <<
BTW – If you issue the mapping/scale command and hold down the Alt key while
selecting the object,
3DS will automatically scale the mapping coordinates to fit the mesh exactly.
Terry Gilbert
Forcade & Associates
Ahh! Thanks for the additional data, Terry.
I forgot about that.
Bob