While the Cool VL Viewer already has offered extended/enhanced environment (from now on, referred to as "EE") inventory assets and editing support for months (together with a unique, real time, EE settings translation for rendering with the legacy renderer), it today brings you genuine EE rendering as well, in the new v1.27.0.0 experimental viewer.
However, and since I'm
quite dissatisfied with how LL dealt with EE rendering (by ruining the speed of the renderer), I
refuse to get rid of the good old Windlight (from now on, referred to as "WL") renderer, and therefore implemented a dual (!) rendering engine into v1.27.0, with two different sets of shaders and a dual-path rendering pipeline.
You can choose whichever rendering engine suits your needs (better looking environment, or higher rendering speed).
At a user level, the whole stuff is dealt with a simple "Extended environment shaders" check box in the shaders section of the "Preferences" floater, "Graphics" tab, "Renderer settings" sub-tab.
Note however that toggling this setting on or (in a lesser measure) off, might cause rendering glitches if done once logged in (because some loaded textures may have a wrong color space set), so if you toggle it, it is best doing it in another, far sim than in the one you wish to use the viewer (so that the badly set textures will get unloaded on returning TP).
For now, and since WL to EE real-time settings translation is not (yet) implemented,
you loose the ability to use the WL settings editor while in EE rendering mode. EDIT: implemented in v1.28.0.0.
For the same reason and since EE relies on sim server support for EE settings (even for the default Sunrise, Midday, Sunset and Midnight settings) and parcel environment support, EE rendering, while available in OpenSim, is rather moot and results in just a fixed/frozen and weird looking environment (at least, it does not crash the viewer neither the sim). EDIT: implemented in v1.27.0.3.
You will notice some render glitches with some particle systems (especially those with emissive or glow textures), but these are the same glitches as the ones encountered with LL's viewer (and yes, I do have
the latest softenLightF.glsl shader fix implemented).
Also, a known bug of my implementation is that the new alpha emissive and full bright textures batching (RenderAlphaBatchEmissives and RenderAlphaBatchFullbrights) mechanism is currently broken (just do not enable these debug settings, and everything will work fine). EDIT: fixed in v1.27.0.1.
As for the benefits and drawbacks of EE rendering, I'll let you make your own mind and be judge about them, but as far as I am concerned, getting a halved frame rate (in relatively complex sims) is just not acceptable to gain a prettier sky... The difference between EE and WL gets dramatic in alpha/emissive/glow-textures-heavy sims, while it's only marginal in lightweight sims.
On the bright side, the Cool VL Viewer v1.27.0.0 is about 15-20% faster in average than LL's viewer (with "RenderAlphaBatchEmissives" turned off in both viewers, but even with it on in LL's viewer and kept off in mine, and as long as not too many emissive textures are around, the Cool VL Viewer is still faster).
I'll keep updating the v1.27.0 viewer in the coming weeks, until I am satisfied with its status, at which point it will be promoted as the v1.28.0 stable viewer (and will deprecate v1.26.24). Note that this means loosing the compatibility with super-old computers that could not do rendering with "Basic shaders" enabled (this setting is now always on and cannot be disabled in v1.27.0). But disabling basic shaders already caused a whole lot of rendering issues in previous versions, so I do not think it will be a big loss for anyone.
Feel free to comment in this forum thread.