Hello,
Until the challenges with OpenGL API are solved, we should look into different manner to visualise altitude changes on a map.
There's a big difference between what looks nice and what we actually need. I love 3D views but what I am missing is a way for my brain to know what are peaks and what are valleys in maps and specially orthophotos . There are different ways to achieve that result, static methods and dynamic methods.
1. Would it be a solution to generate some hillshade on top of the view? This is a static method. The depth information is communicated with a single picture.
Hillshade maps already exist but what could be even more useful is a user defined hillshade where it is possible to define the coming direction of the light.
One needs to define one 3D vector v1 from the chosen position of the sun to say the center of the map.
A field of ground normal vectors of ad-hoc density must also be calculated. Each ground vector v2ij is the surface normal vector pointing upward at point ij
The angle Aij is the angle between v1 and v2ij. If |Aij| is between 90° and 0° then the shading is on at point ij . The shading intensity is then inversely proportional to |Aij|.
2. Generating altitude contour lines could also help to produce a sensation of depth. The distance between curves (delta altitude), color should be user defined.
3. Finally, the most interesting concept.
It is possible to give a real 3D depth to a top view. This is a dynamic method. The depth information is communicated by displaying a succession of pictures by panning the view. Try panning a top view in Google earth at reasonable altitude. It will give you a good idea of what I am talking about.
When panning the view, pixels at higher altitude translate more than at lower altitude. The translation is inversely proportional to the distance between the eye and the terrain. This is of course function of the altitude of the terrain.
This technique can be applied together to any data in Locus: maps, overlays and wms to indifferently map data to the the topography. Used separately on different data sources could create some interesting 3D layering effects.
The question is if the transformation made on the screen pixel grid can be calculated in real time or does it slow down the screen refresh rate?
What do you think of these suggestions?
Cheers
This reply was created from a merged topic originally titled
Ideas to implement a pseudo 3D visualisation while waiting for a full 3D-Locus.
