Question

Does someone know a fast way to invoke shader processing via DirectX?

Right now I’m setting shaders using D3DXCreateEffectFromFile calls, which create shaders in runtime (once per each shader) from *.fx files.

Rendering part for every object (every patch in my case – see further) then means something like:

// --------------------
// Preprocessing
effect->Begin();
effect->BeginPass(0);
effect->SetMatrix (or Vector or whatever - internal shader parameters) (...)
effect->CommitChanges();

// --------------------
// Geometry rendering

// Pass the geometry to render
// ...

// --------------------
// Postprocessing

// End 'effect' passes
effect->EndPass();
effect->End();

This is okay, but the profiler shows weird things – preprocessing (see code) takes about 60% of time (I’m rendering terrain object of 256 patches where every patch contains about 10k vertices).

Actual geometry rendering takes ~35% and postprocessing – 5% of total rendering time.

This seems pretty strange to me and I guess that D3DXEffect interface may not be the best solution for this sort of things.

I’ve got 2 questions:

1. Do I need to implement my own shader controller / wrapper (probably, low-level) and where should I start from?

2. Would compiling shaders help to somehow improve parameter setting performance?

Maybe somebody knows how to solve this kind of problem / some implemented shader interface or could give some advices about how is this kind of problem solved in modern game engines.

Thank you.

Answer 1

Actual geometry rendering takes ~35% and postprocessing – 5% of total rendering time

If you want to profile shader performance you need to use NVPerfHud or something similar. Using CPU profiler and measuring ticks is not going to help you – rendering is often asynchronous.

Do I need to implement my own shader controller / wrapper (probably, low-level)

Using your own shader wrapper isn’t a bad idea – I never liked ID3DXEffect anyway.
With your own wrapper you’ll have a total control of resources and program behavior.
Whether you need it or not is for you to decide. With ID3DXEffect you won’t have a warranty that implementation is as fast as it could be – it could be wasting cpu cycles doing something you don’t really need. D3DX library contains few classes that are useful, but aren’t guaranteed to be efficient (ID3DXEffect, ID3DXMesh, All animation-related and skin-related functions, etc).

and where should I start from?

D3DXAssembleShader, IDirect3DDevice9::CreateVertexShader, IDirect3DDevice9::CreatePixelShader on DirectX 9, D3D10CompileShader on DirectX 10. Also download DirectX SDK and read shader documentation/tutorials.

Would compiling shaders help to somehow improve parameter setting performance?

Shaders are automatically compiled when you load them. You could compiling try with different optimization settings, but don’t expect miracles.