Reorganizing vertex input structure

Graphics and GPU Programming Programming

Started by Dawoodoz October 28, 2011 07:31 PM

11 comments, last by Dawoodoz 12 years, 5 months ago

482

Author

October 28, 2011 07:31 PM

I use DirectX 11 and shader model 4.

I am reorganizing the vertex structure in my graphics engine to allow bone animation.
The problem is that I have packed both normals and selection in "NORMAL" by giving xyz to the normal and w to selection but I don't want the users to rewrite their shaders.

HLSL:



	struct VS_structure {

		float4 Pos : POSITION;

		float4 Tex : TEXCOORD;

		float4 Color : COLOR;

		float4 NormalAndSelected : NORMAL;

		float4 A : BINORMAL;

		float4 B : TANGENT;

		float4 BoneData : TEXTURE;

	};

These macros are working for most shaders but not the ones that are already accessing specific elements of the normal.
HLSL:



	#define Normal NormalAndSelected.xyz

	#define Selected NormalAndSelected.w

How do I define 2 variables on the same registry in VS_structure?

MJP

20,295

October 28, 2011 07:37 PM

What's the point of packing an extra value in the normal?

The Blog | The Book

Dawoodoz

482

Author

October 28, 2011 07:39 PM

What's the point of packing an extra value in the normal?

I can't find more names for constant registers.

Codarki

462

October 28, 2011 08:01 PM

You can separate the input structure of shader and a structure which users can operate on. HLSL compiler will optimize it away. Say:





struct VS_packed_input

{

    float4 Pos : POSITION;

    float4 NormalAndSelected : NORMAL;

};



struct VS_input

{

    float4 Pos;

    float3 Normal;

    float1 Selected;

};



struct VS_output

{

    float4 Pos;

    float3 Normal;

    // stuff

};



VS_input unpack(VS_packed_input input)

{

    // unpack and return

}



VS_output VS(VS_packed_input packed_input)

{

    VS_input input = unpack(packed_input);

    // do stuff and return VS_output

}

Codarki

462

October 28, 2011 08:03 PM

What's the point of packing an extra value in the normal?

It's about minimizing the hardware interpolators.

Dawoodoz

482

Author

October 28, 2011 08:28 PM

I might have to tell the users to write "(Input.Normal).xz" instead of "Input.Normal.xz" to avoid messing up the error messages.

Codarki

462

October 28, 2011 08:34 PM

I might have to tell the users to write "(Input.Normal).xz" instead of "Input.Normal.xz" to avoid messing up the error messages.

Can you elaborate a bit about what errors?

Dawoodoz

482

Author

October 28, 2011 08:39 PM

If I go around the user too much, making a mistake and getting reports from the HLSL compiler will make no sense. Even the macros can cause confusion when the compiler is quoting something that does not exist in the shader.

Codarki

462

October 28, 2011 08:45 PM

I misunderstood, I thought the errors would come from my example. I understand the macros will not work that way. Macros usually ruin the error messages aswell. You could surround the macro values with parantheses. I was only suggesting a solution without macros, a one which I've implemented few times.

Can you say who are these users which you're talking about?

Dawoodoz

482

Author

October 28, 2011 08:53 PM

I misunderstood, I thought the errors would come from my example. I understand the macros will not work that way. Macros usually ruin the error messages aswell. You could surround the macro values with parantheses. I was only suggesting a solution without macros, a one which I've implemented few times.

Can you say who are these users which you're talking about?

The engine is mostly used from Visual Basic and I try to keep it simple for beginners.

The best solution would be to find another constant register name. It would be weird if there was only 7 names since that is not a power of 2.

Edit:
There was only 7 names