Hi All,

Having seen some recent screenshots from X-Plane 10, I've been
thinking about ways to improve our random scenery, in particular

At present, we have random building scattered over the scenery, based
on .ac models, plus the Urban shader.

The former are limited in that performance suffers significantly as
density increases, and there is little control over their placement.
The Urban shader provides an good impression of a complex city-scape,
but the sides of the buildings are rather gray, and the visuals suffer
at low viewing angles. It also has a significant performance impact.

I'm wondering whether there is any mileage in using a variant on the
scheme we use for random vegetation to create a cityscape. As you may
be aware, the random vetegation uses a small number of geomerties
instantiated all over the terrain, and uses a vertex shader (which is
much cheaper than a fragment or geometry shader) to provide height,
width and texture information.

Of course, there's no point at all in doing this unless it provides
better performance than the urban shader.

The Default materials.xml tree density is 4000m^2, or a tree per
63mx63m square (ish). The trees themselves have similar geometric
complexity to a cuboid (same number of vertices), but buildings don't
generally have any alpha blending requirements. So to a first level of
approximation, we should be able to populate the urban area with
textured cubeoids at the same density as the trees for a similar cost

To provide more interesting buildings, I'm anticipating using a cuboid
per floor, plus a modified cuboid for the roof, so probably ~ 4x the
complexity of trees geometrically for a 3 storey building.  Obviously
there would be XML controls in materials.xml (or a linked XML file)
for the length, width, number of floors, textures, and roof.

At the same time, I'm anticipating aligning the buildings with the
texture, and probably using a second texture as a mask to indicate
where buildings may, or may not, be placed. This latter technique may
also have applications for the trees, so that trees only appear a the
edges of fields, or in the "rough" of golf courses.

I'm interested in peoples opinions on this, and in particular what
their view is of the current forest and urban shader performance. It
may be that my system is unique in that one is cheap and the other
expensive, and this is all pointless!



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