[ogre 13] WBOIT / early-z / rendering opaque objects only?

[loath]

how do you tell ogre to render only opaque objects in a pass? i'm looking through the WBOIT code in ogre 13 and curious.

the reason i'm asking is:

1) so i can use WBOIT outside of RTSS and
2) i'm curious if an early-z pass would improve performance and create a scene depth map for lighting and post processing purposes. is there an example of this anywhere? is the deferred sample's GBUFFER compositor / shaders the closest? and then just use the same depth pool so later stages can "early out"?

thanks!

[paroj]

the WBOIT sample puts the transparent objects on a non-standard render-queue manually:
https://github.com/OGRECave/ogre/blob/f ... ency.h#L58

and then explicitly triggers that in the compositor using the same depth pool.

You can certainly do early-z the same way. The "PSSM/shadow_caster" material does exactly what you want as it "just writes depth".

[loath]

You can certainly do early-z the same way. The "PSSM/shadow_caster" material does exactly what you want as it "just writes depth".

great, thanks!

the WBOIT sample puts the transparent objects on a non-standard render-queue manually:

oh ok that makes sense. am i correctly understanding how render queues and compositors work?

render queues:
1. each render queue is executed and drawn into the render target in order.
2. compositors first_render_queue / last_render_queue default to essentially "all queues" (except overlays etc) so this is why compositors are typically run at the end. (ex. for post processing)
3. you can override first_render_queue / last_render_queue to run a compositor between a specific set of render queues.

WBOIT example:
1. render queues from 0 to 95 are drawn into the "default" render target.
2. the WBOIT compositor is triggered for render queues 96 and 97

• a. WBOIT compositor copies the "default" RT into "opaque" RT.

• b. WBOIT renders queues 96 and 97 into "accum" RT.

• c. "opaque" RT is copied back into the original render target.

• d. a WBOIT fragment shader takes "accum" RT and using the WBOIT algorithm writes the transparent pixels into the "default" RT.

3. remaining render queues are drawn into "default" RT. (98+ until overlays)
4. any other "default" compositors may be executed. (ex. post processing)
5. overlay render queues executed.

final question:
does this copy from the "default" RT to "opaque" RT or is "opaque" just an alias? (from "compositor WBOIT" in ogre samples)

Code: Select all

 target opaque
        {
            input previous
        }

many thanks!

[paroj]

all is correct except that there is no implicitly copy: for the first compositor "input previous" is just a special alias for "pass render_scene", where the viewport parameters are used instead of overriding them.

also, internally there is only one "pass render_scene" per target section, so first_render_queue / last_render_queue simply set which renderqueues are executed.

[loath]

thanks! i had no idea this is how it worked.