Re: Postprocessing - binding shader variables

On 01.07.2013 02:56, Pedro Arthur wrote:
> I'm trying to properly bind the input textures to the posteffect's
> layer's shader, and I have some questions:
> What's the correct way to do that?

See below.

> What csShaderVariableStack does?

This is a helper class to build the set of shader variables used for
rendering meshes:
Conceptually, you start off with an empty stack, and merge other
contexts onto the “front” or “back” of the stack. (Merging onto the
front means that an SV is used if no other is used yet; Merging onto the
back means a previously set SV is replaced.)
This system is used to implement the “order of preference” stated here:
http://crystalspace3d.org/docs/online/manual/Shader-System-Overview.html#9

AFAICS in the post effects system there's a method that uses such a
stack is used to combine the SVs attached to a layer with other SVs that
provide input textures (PostEffect::GetLayerRenderSVs()), but apparently
this method is only used by the HDR stuff.

The collection of SVs for “generic” post-effect rendering is done by
DimensionData::UpdateSVContexts(). There, the layer SV context is used
as a base for an “overlay” SV context (a special implementation that
adds SVs on top of the base SV without modifying it), and the automatic
inputs are “overlaid”.

That said,
- You could add your SV to the layer SV context. (Note however this SV
context is mainly intended for user-provided SVs, overriding these with
predefined/automatic SVs isn't that nice.)
- You could add your SVs “manually” the same way as done in
UpdateSVContexts().

Note that piling more SVs onto the end of UpdateSVContexts() probably
wouldn't improve it's readability. Also, it's a bit unfortunate that
both GetLayerRenderSVs() and UpdateSVContexts() seem to have some
overlapping functionality. Maybe you can find time for a little
refactoring here...

-f.r.

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