-w = (0, 0, Lpos.z) so the last expression doesn’t make sense because only z-component will be non-zero.
So I had to guess your intentions as this where 15 is plane distance.
float2 lightDirection = lightPosition.xy - pixelPosition;
float2 offset = lightDirection * (15 / lightPosition.z) * screenMultiplier;
Is that correct?
My intentions are correct, that’s why w.z is used, which is z component of w
Ah, I see. I thought the “.” was something else.
sorry about misunderstanding.
Here is Pixel shader
float4 OmniLightPS(VertexToPixel PSIn) : COLOR0
{
//We calculate in world space
//simple transform into world space (where one pixel is one world unit), this is our current point on background plane
float3 pointWS;
pointWS.xy = (PSIn.TexCoord.xy) * viewport;
pointWS.z = -planeDistance;
//Vector between light and point
float3 lightVec = lightPos - pointWS;
//vector from plane we are projecting to, I leave this as whole float3 so its obvious what that was in equation, reduce this to float
float3 w = float3(0,0, -lightPos.z);
//light vec is from point to light so whole thing is *-1 which remove negative signs
float s = w.z / lightVec.z;
float3 samplePoint = lightPos + s * lightVec;
//sample texture, don't forget to get sample point coordinates back to screen space
float shadowTerm= tex2D(Sampler, samplePoint,xy/ viewport).a; //as Sample point Z is 0 as that was plane were targeting
//calculate attenuation
float intensity = saturate(1.0f - length(lightVec) / (attuneation)) ; //sorry about type in attenuation
return float4(PSIn.Color.rgb * intensity * (1 - shadowTerm) ,1);
}Okay, thanks. So the expression I wrote before is correct, right?
no, offset itself is (-light.z / lightVector.z) * lightVector
lightVector is whole vector, not just direction (that implies normalized vector)
I’m calculating the offset from the destination pixel not the light position, sorry forgot to mention that.