World Machine is working with a heightfield of finite resolution that is completely calculated within the extents of your work area in the calculation phase. Any time you make a change to the terrain you must recalculate of course. For the lowest resolution preview it is fast to do this, but WM also does not include atmosphere and clouds nor surface texturing, let alone complex displacements like TG2 does.
Because of the view-dependent detail of the terrain the TG2 realtime preview has to work the way it does to give you a proper preview of the scene. The only alternative would be precomputing the terrain at an overall lower detail across a specific area surrounding the viewer. This would take a similar amount of time to calculating a World Machine terrain and then would only be valid as long as you stayed within that pre-computed terrain area - as soon as you moved outside of it you'd need to do another lengthy pre-calculation phase. The detail would also necessarily be lower because it would have to be constant across the terrain area, whereas currently it's calculated at higher detail closer to the camera, allowing you to see very small details when close to the terrain for example.
So long story short the current preview is non-ideal, but alternative solutions don't seem much better at this point. We'll certainly be working on improving the update speed and feedback of the preview, but given the way TG2 works and the power and flexibility it has, it's extremely difficult to give you similar preview styles to other 3D apps like Wireframe that are often faster. In this case they simply wouldn't be because the bottleneck is in computing the fundamental terrain shapes, not in the display of them. You can already turn off computation of lighting and atmosphere to speed things up, which would essentially be equivalent to wireframe speed.
- Oshyan
