Request: Indicator if a camera is realtime in shader

[klepto2]

While testing the new Effect feature in the Editor i encountered a small problem with my posteffect shaders.

Some of my effects use a technique called reprojection, actually this is a very basic implementation but improves the perfromance a lot. What it does, is that it uses a 4*4 Bayer filter to determine which pixel needs to be calculated based on the fragment coordinate and the current frame. If a pixel is not meant to be calculated it reads the result from the previous frame (reprojecting the current uv to the previous uv). This means over a period of 16 frames the whole buffer is calculated.

Unfortunatly this is not working in the editor. I believe it might be due to the fact (correct me @Josh if i am wrong), that the editor doesn't use async rendering and the camera is not rendered in realtime. so if we can get a flag which indicates if a shader is invoked from the editor, we could disable some features (reprojection in this case) and use the pfx correctly in the editor.

I will write a very basic shader which will simulate the error and attach it later here.

[Josh]

For this reason, I was considering making 3D viewports render twice in the editor each time, if SSR is enabled.

[klepto2]

ok, that makes sense, but in that case a dynmic calculation how many frames needs to be generated maybe needed. While 2 frames for ssr are enough (previous + currentframe) it would't be enough if you use the full power of reprojection and regenerate the whole view over multiple frames. In my case the editor would need to render 16 frames to update the viewport. 

Maybe something like the premulitplyalpha option in a posteffect file would be needed. Wven if its for the editor alone. Maybe somehting like:

EditorRedrawFrames: 16 or so. Then the editor could use the maximum of the that value based on the posteffects attached.

[Josh]

Hmmm, that is a lot! I think your idea to disable reprojection based on a camera setting is probably better.

[klepto2]

Just an idea: Now as normally the glsl is compiled at runtime, we could use that fact to introduce global defines which are added to the preprocessed shaders. 

this could also be extended to add functionality or inject custom macros, but that might be a small overkill for now. I could imagine a system like this:

//Before loading any shader a function needs to be called to register global definitions. 
//As it will be a advanced feature i would place it like this: 
Render::GraphicsEngine::instance->AddShaderDefine("Editor");
Render::GraphicsEngine::instance->AddSahderDefine("saturate(x) clamp(x,0,1)");

the generated code in glsl  would look like this:

#version 460
...

#define Editor
#define saturate(x) clamp(x,0,1)


void main()
{
#ifdef Editor
	....
#endif
}

just an idea.