Adding to 3D Features

Mike TrulyMike Truly Global Mapper UserPosts: 42Trusted User
edited April 2010 in Technical Support
Let's say I have some geo-rectified images in GM11 that I want to bring into my 3D application where I have a 3D terrain model. The images will be planar mapped from the top down onto the terrain.

If the 3D terrain has very prominent features that are also visible in the images, it is relatively easy to pos/rot/scale the UVW mapping so that the rectified image is in the right spot on the model. But if the features are very faint, it can be difficult to get the UVW alignment correct.

In the 3D program, a model can have unlimited UVW mapping and the materials can be very sophisticated such that multiple-resolution textures can be used. (for example, a material can be setup so when looking towards a horizon... a high resolution texture is used for the foreground, medium texture for mid-ground, and low texture for far-ground, etc. These textures and distances can be animated giving the impression of a more complex scene).

I'm wondering... when a georectified image is within the bounds of the terrain model, it would be helpful to be able to output 3D geometry (as a DEM) with the initial terrain model that would define the bounds of the rectified image to help with alignment later. So for example, the user would draw a polygon in GM that would be incorporated into the exported DEM. Because it would be part of the exported DEM, it would already be perfectly aligned/scaled to the terrain. The user could then use this as reference to align the UVW mapping and then later delete the unneeded polygon.

Can this be done with a DEM? It would seem that it's just a 3D mesh so some extra polygons wouldn't matter. Can GM11 do this already?

(I should note that when I export the rectified images, I am drawing a box and including a bit of the false color terrain around the edges of the image to help with alignment. This works OK sometimes but depends on the prominence of the terrain to work well. Also, because of the texture blending technique mentioned above, it is not ideal to have a neon-colored edge around the bitmap which can appear at in-opportune times. It would be better to have no color edge beyond the texture itself... alpha).



  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited April 2010

    Most of the DEM formats are just a regular grid of elevation values, so there is not any way to add any additional features, like polygons to it, other than actually altering the terrain values themselves in the DEM, which is likely not what you want. Does your 3D program support loading additional vector files, like maybe DXF or Shapefiles? If so you could export your polygon to one of those formats and load that over the DEM.


    Global Mapper Support
  • Mike TrulyMike Truly Global Mapper User Posts: 42Trusted User
    edited April 2010
    Thanks Mike. The 3D app does support loading many types of formats including DXF. Problem is I am not well versed in using all of them and many times the model will not come in at the proper position/scale depending on the format. I will look into the options of DXF and do some experimenting to see if it will import in the proper scale.

    Thanks again.
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