How to pass a big (60+) amount of variables to an HLSL pixel shader?

Question

I am in trouble at trying to pass a big amount of variables needed for my pixel shader computations.

After trying and failing to link my struct to a cbuffer (data alignement mismatch) I tried passing my variables first to the vertex shader (with an D3D11_INPUT_ELEMENT_DESC / CreateInputLayout) with the intent to link them to the pixel shader through semantics but I hit the 32 shader inputs limit.

I am really stuck (and quite a noob at DX). What is a common / standard way to do this ? Can I only rely on a cbuffer ? Is creating a D3D11_INPUT_ELEMENT_DESC / CreateInputLayout even possible for the pixel shader ?

Example struct I want to pass to my pixel shader :

struct SceneParamsInterface { bool DEAOEnabled; XMFLOAT4 DEAOColor; double DEAOPow; bool lightEnabled; XMFLOAT4 lightColor; XMFLOAT3 lightDirection; bool lightMultiply; double lightMultiplyFactor; bool ambiantLightEnabled; XMFLOAT4 ambiantLightColor; bool HSEnabled; int HSSpread; bool fogEnabled; XMFLOAT4 fogColor; double fogDistanceMax; bool glowEnabled; XMFLOAT4 glowColor; double glowRadius; XMFLOAT4 skyColor; bool skyBoxEnabled; //uniform sampler2D skyBoxTexture; int skyBoxScheme0; // top int skyBoxScheme1; // left int skyBoxScheme2; // front int skyBoxScheme3; // right int skyBoxScheme4; // back int skyBoxScheme5; // bottom int skyBoxRotate; double skyBoxRotateSpeed; XMFLOAT3 skyBoxRotateAround; bool orbitTrapsEnabled; int orbitTrapsId; XMFLOAT4 objectColor; };

Thanks!

Can you tell us what the parameters are that you are passing and what you are doing with them in the shader? — Alan Wolfe
– Alan Wolfe, Commented Aug 16, 2015 at 0:54
@AlanWolfe I didn't write the pixel shader code yet (I am porting GLSL code to HLSL) but I need all these variables (63+) available in my pixel shader for raytracing computation. I have 4 C++ structs for that purpose - see the one I posted up there. — PinkTurtle
– PinkTurtle, Commented Aug 16, 2015 at 12:25
Seeing nobody answered yet - I dont know much about dx11, but if you used openGl you could use texture or a buffer where usually geometry is stored. — wondra
– wondra, Commented Aug 16, 2015 at 21:51
This is the classic "Direct3D 9" design where you had to use a global set of constants. This is an extremely inefficient way to use Direct3D 11 Constant Buffers. See Windows to Reality: Getting the Most out of Direct3D 10 Graphics in Your Games--yes this is a Direct3D 10 era talk but it 100% applies to Direct3D 11 too. — Chuck Walbourn
– Chuck Walbourn, Commented Aug 18, 2015 at 3:02

cfehunter · Accepted Answer · 2015-08-17 05:59:51Z

Use several constant buffers and group variables together based on how often they change.

If your variables are fairly static ( or just huge ) you may be better off converting values into a texture and extracting them in the shader.

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