*spin-off* Battlefield 3 on Consoles

[Ruskie]

You don't need to go sub HD if you do light prepass (the original two pass version). You only need one (32 bit per pixel) render target, since you only need normal vector and specular exponent for the lighting pass. Color is added in a secondary geometry pass. Secondary geometry pass is the reason why light prepass requires more CPU cycles and GPU cycles (vertex transform twice).

However you can do light prepass in a single pass. That is pretty much comparable to fully deferred. It has slightly less light overdraw cost (color is composited after lights) compared to fully deferred, but the lighting formula is more restricted (single color specular, etc).

Does light pre pass always require 2x geometry pass?I mean,if its like that,wouldn't tiling be less expensive assuming you are using deferred shading which does not need secondary geometry pass?

Oh,just out of curiosity,how much rendering budget do you spend on geometry in Trails HD?

 

[sebbbi]

Does light pre pass always require 2x geometry pass?I mean,if its like that,wouldn't tiling be less expensive assuming you are using deferred shading which does not need secondary geometry pass?

If you do light prepass in a single pass, you need an extra render target to store the color data (just like full deferred does). This means your g-buffer size is the same as with full deferred. So you have to go slightly sub HD if you want to avoid tiling. And that's what Crytek has done in their newest tech (1152x720). If I understand correctly, they are still using single pass version of light prepass (at least they were experimenting with it during the production according to their earlier white papers).

Oh,just out of curiosity,how much rendering budget do you spend on geometry in Trails HD?

Trials HD is a simple indoor game. It has only 40 meters of max view distance (everything is fogged out after that). The game does not have that much visible geometry to render and doesn't even use a LOD system. It's never vertex processing bound.

Things are quite a bit different in Trials Evolution. The game has view distance of 2000 meters, and has up to 10x objects visible simultaneously (more objects in one frame that Trials HD had in a whole track). We added a lot of new features to reduce the geometry cost. A LOD system is of course a must for free roaming outdoor games. We do not have any backdrops (since you can go everywhere), everything is real geometry (or impostors). Our geometry has really tight vertex formats. We managed to cram everything in 16 bytes (minimizing vertex BW and fetch cost). Also our vertices do not have precalculated tangent matrices anymore. We calculate them in pixel shader (using screen space derivatives). This saves a lot of vertex shader ALU (no need to fetch and transform tangent matrix). A small and compact vertex is also useful since we stream all our geometry data. I will post detailed information about our geometry compression and processing, when I have time to write a technical post mortem of our technology (it's getting a little big off topic in this thread).

 

[NRP]

Perhaps sebbbi, but yours is the good kind of OT.