David, Either I'm not following you or I haven't conveyed clearly what I'm doing. The grid that I create has the same resolution as the TIFF. My original message was slightly inaccurate - what I do is Construct a grid (with dummy data) then use Replace twice to transfer its positions and data to the TIFF field. The result of this is a regular field with colors, in the same frame of reference as the elevation data, but with the TIFF resolution. I then Map elevation data onto this field. The image at this point displays perfectly. The final step of RubberSheeting makes the image go bad, but I found that simply adding an AmbientLight fixes it up.
Just to be certain, I tried Refining the elevation data before Mapping it, but this made no difference. If anyone is interested I could email a sample of the screwy image. Gib > -----Original Message----- > From: David Thompson [mailto:[EMAIL PROTECTED] > Sent: Monday, September 17, 2001 4:04 PM > To: [email protected] > Subject: RE: [opendx-users] Clipping > > > Gib, > > This is probably due to the fact that your Image has much more > resolution than the grid you're mapping it onto. In order to improve > this, use the Refine module on your grid and see if that helps. > > David > > >You will not be surprised to learn that my problems with Map > resulted from > >an oversight. Because I wasn't careful with my coordinates, > I was actually > >mapping elevations from an area outside my data region > (which doesn't fill > >the rectangle), therefore the 0 values were correct. Sorry to waste > >bandwidth. > > > >But wait, there's more! I am now rendering my image with > the TIFF painted > >on the rubbersheeted surface. To recap, I first create a > grid with the same > >connectivity as the TIFF, but with positions in the frame of > reference of > >the elevation data. I then Replace the colors in this field > with the TIFF > >colors. At this stage I have a nice looking image. Meanwhile I have > >Imported the elevation data (which when Rubbersheeted produces a nice > >surface). I then use Map to put elevations into the object > with the TIFF > >colors. If I render at this point it still looks fine. The > final step is > >to Rubbersheet the field. The image produced does not look > nice. The > >elevations are correct, and the colors are roughly right, > but there is an > >ugly graininess. Zooming in shows that something bad has > happened, an odd > >effect that is hard to describe but looks a lot like a bug. > > > >I have found that the image is cleaned up if I Collect it with an > >AmbientLight. Since AmbientLight removes the default > lighting, which is > >ambient [0.2 0.2 0.2] plus a distant light, I'm guessing > that the problem is > >related to what happens to the image lighting/colors when > Rubbersheet is > >applied. Anyway, I now have something useable, and have > learned a lot > >through all this. Thanks to all who offered help. > > > >Gib > > > > > -- > .............................................................. > ............... > David L. Thompson Visualization and Imagery > Solutions, Inc. > mailto:[EMAIL PROTECTED] 5515 Skyway Drive, > Missoula, MT 59804 > Phone : (406)257-8530 > NOTICE - This e-mail is only intended to be read by the named recipient. It may contain information which is confidential, proprietary or the subject of legal privilege. If you are not the intended recipient please notify the sender immediately and delete this e-mail. You may not use any information contained in it. Legal privilege is not waived because you have read this e-mail. For further information on the Beca Group of Companies, visit our web page http://www.beca.co.nz
