Introduction to 3D Game Programming with DirectX.9.0 - F. D. Luna

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Note: Since we are using pixel shaders, we will need to remember to change the compile target to a pixel shader target (e.g., ps_2_0) instead of a vertex shader target (e.g., vs_2_0). The compile targets are specified through a parameter of the D3DXCompileShaderFromFile function. See section 16.2 for details.

18.3.2 Creating a Pixel Shader

Once we have the compiled shader code, we can obtain a pointer to an

For example,Tsuppose the variable shader is an ID3DXBuffer that contains the compiled shader code. Then to obtain an IDirect3DPixelShader9 interface, we would write:

IDirect3DPixelShader9* MultiTexPS = 0; hr = Device->CreatePixelShader(

(DWORD*)shader->GetBufferPointer(), &MultiTexPS);

Note: To reiterate, the D3DXCompileShaderFromFile is the function that would return the compiled shader code (shader).

18.3.3 Setting a Pixel Shader

After we have obtained a pointer to an IDirect3DPixelShader9 interface that represents our pixel shader, we can enable it using the following method:

HRESULT IDirect3DDevice9::SetPixelShader(

IDirect3DPixelShader9* pShader

);

The method takes a single parameter where we pass a pointer to the pixel shader that we wish to enable. To enable the shader we created in section 18.3.2, we would write:

Device->SetPixelShader(MultiTexPS);

Team-Fly®

Introduction to Pixel Shaders 325

18.3.4 Destroying a Pixel Shader

As with all Direct3D interfaces, to clean them up we must call their Release method when we are finished with them. Continuing to use the pixel shader we created in section 18.3.2, we have:

d3d::Release<IDirect3DPixelShader9*>(MultiTexPS);

Introduction to Pixel Shaders 327

//

// Main

//

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PS_OUTPUT Main(PS_INPUT input)

{

//zero out members of output PS_OUTPUT output = (PS_OUTPUT)0;

//sample appropriate textures

//combine texel colors vector c = b * s + t;

//increase the intensity of the pixel slightly c += 0.1f;

//save the resulting pixel color output.diffuse = c;

return output;

}

First the pixel shader declares three sampler objects, one for each texture that we are blending. Next the input and output structures are defined. Notice that we don’t have any color values input into the pixel shader; this is because we are using the textures exclusively for coloring and lighting; that is, BaseTex holds the color of our surface and SpotLightTex is our light map. The pixel shader outputs a single color value that specifies the color that we have computed for this particular pixel.

The Main function samples the three textures using the tex2D function. That is, it fetches the texel from each texture that is to be mapped to the pixel that we are currently computing based on the specified texture coordinates and sampler object. We then combine the texel colors with the statement c = b * s + t. Next we brighten the overall pixel color a bit by adding 0.1f to each component. Finally, we save the resulting pixel color and return it.

Now that we have looked at the actual pixel shader code, we shift gears and look at the application code. The application has the following relevant global variables:

IDirect3DPixelShader9* MultiTexPS = 0;

Introduction to Pixel Shaders 329

Device->CreateVertexBuffer(

6 * sizeof(MultiTexVertex), D3DUSAGE_WRITEONLY,

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MultiTexVertex::FVF, D3DPOOL_MANAGED, &QuadVB,

0);

MultiTexVertex* v = 0;

QuadVB->Lock(0, 0, (void**)&v, 0);

v[0] = MultiTexVertex(-10.0f, -10.0f, 5.0f,

0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f); v[1] = MultiTexVertex(-10.0f, 10.0f, 5.0f,

0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f); v[2] = MultiTexVertex( 10.0f, 10.0f, 5.0f,

1.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f);

v[3] = MultiTexVertex(-10.0f, -10.0f, 5.0f,

0.0f, 1.0f, 0.0f, 1.0f, 0.0f, 1.0f); v[4] = MultiTexVertex( 10.0f, 10.0f, 5.0f,

1.0f, 0.0f, 1.0f, 0.0f, 1.0f, 0.0f); v[5] = MultiTexVertex( 10.0f, -10.0f, 5.0f,

1.0f, 1.0f, 1.0f, 1.0f, 1.0f, 1.0f);

QuadVB->Unlock();

//

// Compile shader

//

hr = D3DXCompileShaderFromFile( "ps_multitex.txt",

0,

0,

"Main", // entry point function name "ps_1_1",

D3DXSHADER_DEBUG, &shader, &errorBuffer, &MultiTexCT);

// output any error messages if( errorBuffer )

{

::MessageBox(0, (char*)errorBuffer->GetBufferPointer(), 0, 0); d3d::Release<ID3DXBuffer*>(errorBuffer);

}

if(FAILED(hr))

{

::MessageBox(0, "D3DXCompileShaderFromFile() - FAILED", 0, 0); return false;

}

//

// Create Pixel Shader

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SpotLightTexHandle,

&SpotLightTexDesc,

&count); MultiTexCT->GetConstantDesc(

StringTexHandle,

&StringTexDesc,

&count);

MultiTexCT->SetDefaults(Device);

return true;

}

The Display function sets the pixel shader, enables the two textures, and sets their corresponding sampler states before rendering the quad.

bool Display(float timeDelta)

{

if( Device )

{

// ...camera update code snipped

//

// Render

//

Device->Clear(0, 0, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER,

0xffffffff, 1.0f, 0);

Device->BeginScene();

// set the pixel shader Device->SetPixelShader(MultiTexPS); Device->SetFVF(MultiTexVertex::FVF);

Device->SetStreamSource(0, QuadVB, 0, sizeof(MultiTexVertex));

// base tex Device->SetTexture(BaseTexDesc.RegisterIndex, BaseTex); Device->SetSamplerState(BaseTexDesc.RegisterIndex,

D3DSAMP_MAGFILTER, D3DTEXF_LINEAR); Device->SetSamplerState(BaseTexDesc.RegisterIndex,

D3DSAMP_MINFILTER, D3DTEXF_LINEAR); Device->SetSamplerState(BaseTexDesc.RegisterIndex,

D3DSAMP_MIPFILTER, D3DTEXF_LINEAR);

// spotlight tex Device->SetTexture(SpotLightTexDesc.RegisterIndex, SpotLightTex); Device->SetSamplerState(SpotLightTexDesc.RegisterIndex,

D3DSAMP_MAGFILTER, D3DTEXF_LINEAR); Device->SetSamplerState(SpotLightTexDesc.RegisterIndex,

D3DSAMP_MINFILTER, D3DTEXF_LINEAR); Device->SetSamplerState(SpotLightTexDesc.RegisterIndex,

D3DSAMP_MIPFILTER, D3DTEXF_LINEAR);

// string tex

Device->SetTexture( StringTexDesc.RegisterIndex, StringTex); Device->SetSamplerState(StringTexDesc.RegisterIndex,

D3DSAMP_MAGFILTER, D3DTEXF_LINEAR);