Reconstruct screen coord with worl pos in a surface shader.

Unity Engine
1

Hello,

I’m trying to make my own screen coord instead of using the float4 screenPos; in my surface shader to by pass the texture interpolator limit.

Currently I’m doing it like this :

float2 worldToScreen(float3 pos)
{
	float4 screenPos = mul(UNITY_MATRIX_VP, float4(pos,1));
	return screenPos.xy / screenPos.w;
}

float3 worldPos = IN.worldPos;

float2 screenPos = worldToScreen(worldPos);
		
float2 screenCoord = float2(0,0);

#ifdef SHADER_API_D3D9
	screenCoord = float2(0.5, -0.5)*screenPos + float2(0.5,0.5);
#else
	screenCoord = float2(0.5, 0.5)*screenPos + float2(0.5,0.5);
#endif

I got the same result as if I do it like this :

float2 screencoord = IN.screenPos.xy/IN.screenPos.w;

#ifdef SHADER_API_D3D9
	screencoord.y =1-screencoord.y;
#endif

( By same result I mean I got the same Green Red Yellow gradient )

But if I applied the coord to my noise texture I get this with mine :

and this with the unity screenPos :

With mine the noise is blurry for some reason while with the regular screenPos it’s correct and sharp.

So I tried to change my noise to point instead of Trilinear and it works but if I move the camera I can see weird artefact.

And I got this ( I increased contrast ):

It’s hard to see but the texture is miss aligned or not well place.

Could that be the mesh behind doing this ?

Anyone has faced that problem ?

Thanks :slight_smile:

2

Try possibly adding 0.5,0.5 to the coordinates to center them on the pixel?

3

Thanks, they are half blurred from the original coord now but appearss to be not enough for my BRDF sadly.

With same roughness, I can see that my brdf goes in the wrong way.

Here it’s correct.

4

Maybe I’m not using the right matrix ?

5

Instead of using a surface shader, I made a fragment program much easier to make my stuff working, no more errors now !

Thanks for the help !