February 21, 2011, 10:56:14 am
1) DOUBLE-SIDED MATERIALS
Double-sided materials are already on the wish list and Ferry mentioned that it is possible but that it remains to be seen whether it's fast enough.
Â 2) FLICKERING COPLANAR OVERLAPPING POLYGONS
The problem with coplanar overlapping polygons is that there's no way to tell which material you want to have the highest priority, since they occupy the exact same position from a mathematical perspective, so there will always be flickering regardless of the Z-buffer precision that the software is using. For that reason, I'm not sure what it is you want the "Overlapping polygons check" function to do? Do you want it to highlight areas with coplanar overlapping faces and then ask you to adjust the Depth Offset of each material?
Â 3) FLICKERING COPLANAR OFFSET POLYGONS WHEN THE CAMERA IS FAR AWAY
To make a long story short, flickering is a product of z-buffer precision (depth) and the values of the Near and Far clipping planes of the camera.
:As the distance between near and far clip planes increases and in particular the near plane is selected near the eye, the greater the likelihood exists that you will encounter z-fighting between primitives. With large virtual environments inevitably there is an inherent conflict between the need to resolve visibility in the distance and in the foreground, so for example in a space flight simulator if you draw a distant galaxy to scale, you will not have the precision to resolve visibility on any cockpit geometry in the foreground (although even a numerical representation would present problems prior to z-buffered rendering). To mitigate these problems, z-buffer precision is weighted towards the near clip plane, but this is not the case with all visibility schemes and it is insufficient to eliminate all z-fighting issues.
In other words, we can't make camera settings that prevent flickering polygons in all situations. What we can
do is to make is possible to temporarily adjust the Near/Far clipping planes manually, e.g. as a movie effect and/or as a camera slider in the Weather section, so that you can use a Near clipping plane which is further away when you are looking at the whole 1.5x1.5km model. Alternatively, it could be that the z-buffer precision can be adjusted when rendering stills/movies (at the expense of higher memory consumption/slower speed?). Either way, I'll add a (generic) request for a method to reduce flickering on coplanar (offset as opposed to overlapping) polygons to the wish list in a moment.