Lighting problem in deferred rendering

Hi theScore,

can we see how you reconstruct the position, normal, etc...? ( I think this is the fault )

in what space are they stored in? View, model, perspective?

So to help you further, it would be awesome if we could see this:

• How you store the GBUFFER
• How you use/extract from the GBUFFER
• How you calculate your lighting with the extracted values from the GBUFFER

EDIT: Try to just render the reconstructed normals, positions to see if it looks right. Or use a modern graphics debugger to check the render targets.

Cheers!

-MIGI0027

Hi !

Positions and normals are stored in 2 vectors of 4 floats of 16 bit for each one.

Threre are stored in view space.

Normals are stored like this :

[attachment=22704:normals texture.png]

And positions :

[attachment=22705:positions texture.png]

The positions look off, can we see how you store them?

Another problem may be here (vertex shader from Gbuffer pass) :

        matrix <float, 4, 4> projView = mul(proj, view) ;
	matrix <float, 4, 4> projViewWorld = mul(projView, world) ;
	

	output.RTposition = mul( input.position, view );
 	output.color = input.color ;
	output.RTnormal = mul( input.normal, view);


 	output.texCoord = input.texCoord ;

	output.finalPos= mul( projViewWorld, input.position );

The world matrix is an identity matrix from CPU code, it is for that, that I only multiply positions and normals by the view matrix.

But I am doing :

positions * viewMatrix

normals * viewMatrix

And :

ProjViewWorldMatrix * positions ; //so, not in the same order...

If I change the order in the shader it doen't work (black screen)

Structs in VS :

struct vsIn
{
	half4 position : POSITION ;
 	half4 normal   : NORMAL ;
	half4 texCoord : TEXCOORD0 ; 
	half4 color    : COLOR0 ;
};

struct vsOut
{
	half4 finalPos :SV_POSITION ;
	half4 color : COLOR0 ;
	half4 RTposition : POSITION1 ;
 	half4 RTnormal   : NORMAL   ;
	half4 texCoord : TEXCOORD0 ;

};

And structs in pixel shader :

struct psIn
{	
	half4 finalPos		: SV_POSITION ;
 	half4 color			: COLOR0 ;
	half4 RTposition	: POSITION1 ;
	half4 RTnormal		: NORMAL ;
	half4 texCoord		: TEXCOORD0 ;

};

How are the matrices structued? Row Major? Column Major?

Just to try, transpose the view matrix thats used on the normals and positions, and do as you did before: viewMatrix * position

I use XMMatrixLookAtLH,it is in row major.

I did that and I have the same result than in my first post : (I am not sure that it is what you expected ?)

	matrix <float, 4, 4> projView = mul(proj, view) ;
	matrix <float, 4, 4> projViewWorld = mul(projView, world) ;
	
	matrix <float, 4, 4> transposedView = transpose(view);

	output.RTposition = mul( transposedView, input.position );
 	output.color = input.color ;
	output.RTnormal = mul( transposedView, input.normal);


 	output.texCoord = input.texCoord ;

	output.finalPos= mul( projViewWorld, input.position );
    
	return output ;

Yeah that's what I meant. I've never used XMMatrix, though I should transition to it.

Forget the transposing. When you multiply the view matrix with the position, remember that its a point, so you'd need to write mul(view, float4(input.position.xyz, 1)); But for the normal, leave the w component 0, or instead multiply the normals by the 3x3 view matrix.

Finally, I did that and it works :

	output.RTposition = mul( input.position, transposedView );
 	output.color = input.color ;
	output.RTnormal = mul( input.normal, view );

And I don't understand why positions can't be multipied by a row major matrix... Do you know it ?

Awesome!

Im afraid my knowledge of matrices is very limited, maybe someone with a better overview of the concept can help you. I wouldnt want to pass wrong information to you.

-MIGI0027

Ok thanks for your help, you put me on the line.

if somebody knows for the matrices !...

Without going into theory/details: when it comes to matrices A * B != B * A. If your matrix is different (row vs column) then multiplication order is reversed, you can also reverse it by transposing all matrices.

Ok but here I perform the multiplication in the same order, with the same matrix but transposed once and the other time not transposed, so I don't understand why it works here and with the same processing not ?

// these two are equivalent
output.RTposition = mul( input.position, transposedView ); // transposing reverses order
output.RTposition = mul( view, input.position ); // judging by your projViewWorld matrix this is correct order

// if those lines are correct, then this one is wrong order
output.RTnormal = mul( input.normal, view );