Cpu to shader parameter passing

Question

Hi Guys,

I am trying to pass in a vec3 to the shaders from c++

I can see SRenderObjData has a couple of arrays which might do the job.

m_fTempVars and m_Constants look possible, even m_pShaderParams looks possible, but when I look into the actual shaders, I cannot see where any of them end up.

I can see the obvious ones like

```
float4 PS_ScreenSize : PB_ScreenSize;
```
And all the things like that I would expect to see, but nothing that maps to the data in SRenderObjData.

Anyone point me in the right direction ?

Cheers

Paul

Accepted Answer

Hi @REDACTEDUSER

The way to go here is to declare the parameter by name and enumeration, fill it, and then match it in the shader – here is a pre-existing example for sending a camera's front vector to a shader:

1) The enum declaration (ShaderComponents.h):

```
ECGP_PB_CameraFront,
```
2) The mapping to the shader (ShaderComponents.cpp):

```
SParamDB(PARAM(PB_CameraFront, ECGP_PB_CameraFront), 0),
```
3) The data structure mapped to the buffer (ShaderComponents.h):

```
Vec3 pCameraFront; // ECGP_PB_CameraFront
```
4) The setting of the data into the buffer (D3DHWShader.cpp):

```
        case ECGP_PB_CameraFront:
sCameraFront(sData, r);
break;
```

5) And finally, the shader declaration / matching (in Common.cfx) to be used by the shaders:

```
float4 CameraFrontVector: PB_CameraFront
```

Answer

Ah yes, these can be tricky to find. *g_PS_NearestScaled* is getting used inside of Engine/Shaders/HWScripts/CryFx/ShadowMaskGen.cfx (line 361)

```
float2 ProjRatio = (fSceneDepth

Answer

Hi Binky,

Any progress?

The whole shader system seems to be designed to be obfuscated.

I have written a tool to parse the source code and handle all the conditional flags so I can look at what actually gets passed to the shader compiler, but it's not helped me at all.

For example I can see global constants all over the place. ( I hate global shader constants, but that's another issue). When I look for those values in the C++ code, no sign of them.

```
float4 g_PS_NearestScaled : PF_NearestScaled < psregister = PS_PROJ_RATIO_NEAREST_SCALED; >;
```
If you do a find in files of the source code

```
  Find all "g_PS_NearestScaled", Match case, Subfolders, Find Results 1, Entire Solution, ""
Matching lines: 0 Matching files: 0 Total files searched: 11083
```
Or

```
  Find all "PF_NearestScaled ", Match case, Subfolders, Find Results 1, Entire Solution, ""
Matching lines: 0 Matching files: 0 Total files searched: 11083
```
Nothing,

I can see it is mapped to registers ..

```
#define PS_PROJ_RATIO_NEAREST_SCALED c221
```
But that's all.

This is frustrating as hell, I just need to do some really simple changes to the shaders, but if I cannot pass in a vec3, I am screwed.

Time is running short and there is talk of me flying out to LA to work on a UE4 project, so I really want to get this working ASAP.

Anything you can do to speed things up would be worth beer.

I am going to be at the Lumberyard event in London on Monday, but I would like to be in the position to show something to the guys , rather than turn up and batter them with technical questions.

Cheers

Paul

Answer

I'm looking into an answer on this one for you. I'll get back to you soon.

Answer

Thanks Gene,

That sorted me out. Now I can actually get on with some real work.

Cheers

Paul

Cpu to shader parameter passing

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