Shiver Development: Displacement

As I continue to polish the overall look of the globe - I decided to explore how to display the topology of the earth, which will become more important upon the incorporation of zooming in and out. Another plus for having a working shader pipeline is the ability to write vertex shaders in a way which changes the geometry of the given shader is attached to - better known as displacement.


Fig 1.1: Altitude map provided by the NASA Blue Marble project

Having an altitude map which precisely matches the texture maps I am already using is quite convenient - so there was no need to alter the image or the coordinate mappings in the my shaders. The concept of displacing geometry per vertex is a rather simple one:


Fig 1.2: Formula for displacement per vertex, where:

P0 = original vertex position
p1 = new vertex position
N = vertex normal position
df = normalized displacement factor
uf = user-defined scaling value


Fig 1.3: Diagram of per vertex displacement (Image credit: oZone3d.net)



Fig 1.4: No displacement / displacement comparison in Shiver (wireframe)

My next goal for Shiver is to implement a sunlight calculation system which will auto-generate a texture map accurately representing where how the sun is lighting the earth based on the time of day. Additionally, I plan on (finally) starting the preliminary visualization of the actual seismic events being geomapped.