Part III in VS .NET

Drawer QR Code JIS X 0510 in VS .NET Part III

struct VS_OUTPUT { float4 Pos : float4 Diff : float4 Spec : float2 Tex : };

POSITION; COLOR0; COLOR1; TEXCOORD0;

The semantics appear a third time on the pixel shader inputs:

The semantics tie the vertex shader outputs to the pixel shader inputs. In other words, semantics make it easy to tie vertex shader inputs to the vertex buffer, as well as to tie vertex shaders and pixel shaders together. The diffuse and specular colors are calculated using standard lighting equations:

Out.Diff = I_a * k_a + I_d * k_d * max(0, dot(N, L)); // diffuse + ambient Out.Spec = I_s * k_s * pow(max(0, dot , V)), n/4); // specular

These calculations are done in the vertex shader so that the pixel shader can generate per-pixel lighting results. By doing the calculations in the vertex shader and taking advantage of the interpolation performed in primitive processing, we get per-pixel results without having to settle for doing all the processing on a per-pixel basis. To sample a texture, the pixel shader takes advantage of the vertex shader diffuse and specular colors, and the texture coordinates. Texture sampling requires

So, the effect contains the pixel shader functions and some global variables to set up the pixel shader texture and sampler.

// texture texture Tex0 < string name = "tiger.bmp"; >; sampler Sampler = sampler_state { Texture = (Tex0); MipFilter = LINEAR; MinFilter = LINEAR; MagFilter = LINEAR;

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}; float4 PS( float4 float4 float2 { return }

Diff : COLOR0, Spec : COLOR1, Tex : TEXCOORD0) : COLOR tex2D(Sampler, Tex) * Diff + Spec;

The Tex0 global variable refers to the texture object. The annotation (which is inside the angle brackets) specifies the name of the texture file from which to create the texture object. The Sampler global variable refers to the texture sampler. A sampler not only references the texture object that it will sample from, but it also can contain the sampler state (the filtering options) that are applied when texture sampling is performed. This information is all referred to as sampler state and is contained inside the curly braces. In this case, our sampler object will sample from Tex0 and will use linear filtering modes.

{ Texture MipFilter MinFilter MagFilter }; = = = = (Tex0); LINEAR; LINEAR; LINEAR;

Now that we ve seen the code for initializing the texture and sampler objects, we can look at the pixel shader, which contains one line:

return tex2D(Sampler, Tex) * Diff + Spec;

This code uses the tex2D intrinsic function to perform a 2-D texture sample. Once a color is returned, it s combined with the interpolated diffuse and specular colors that were input to the pixel shader. The result is a pixel color that s a blend of the texture, the lighting, and the material colors. Much like the examples in 9, adding an HLSL pixel shader to an existing effect is pretty easy. It does not change the effect-creation API calls. Simply add a pixel shader function to the effect file, and a pixel shader compile statement to the pass like this:

PixelShader = compile ps_1_1 PS();

Let s move on to the application code that builds the effect. The effect is created with D3DXCreateEffectFromFile.

HRESULT hr; hr = D3DXCreateEffectFromFile( m_pd3dDevice, "Simple_VS_and_PS.fx",

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NULL, // A NULL terminated array of D3DXMACROs NULL, // A #include handler D3DXSHADER_DEBUG, NULL, // memory pool, &m_pEffect, NULL); if(FAILED(hr)) { SAFE_RELEASE(m_pEffect); return hr; } D3DXHANDLE hTech = m_pEffect->GetTechniqueByName("TVertexAndPixelShader"); hr = m_pEffect->ValidateTechnique(hTech); if(FAILED(hr)) { return hr; }

This is unchanged, regardless of whether the shaders are designed in Asm or HLSL, and it does not change if the effect has only a vertex shader, has both a vertex and a pixel shader, or has only a pixel shader. An effect takes care of calling the correct shader compile functions and creating the shader objects so that you don t have to. The render code, shown here, is also unchanged, even though we added a pixel shader to the effect:

// Begin the scene if( SUCCEEDED( m_pd3dDevice->BeginScene() ) ) { // Draw the mesh if(m_pEffect) { D3DXMATRIXA16 matWorld; D3DXMatrixIdentity(&matWorld); m_pEffect->SetMatrix("World", &matWorld); m_pEffect->SetMatrix("View", &m_matView); m_pEffect->SetMatrix("Projection", &m_matProj); m_pEffect->SetTechnique("TVertexAndPixelShader"); HRESULT hr; UINT numPasses, iPass; hr = m_pEffect->Begin( &numPasses, 0 ); for( iPass = 0; iPass < numPasses; iPass ++ ) // all passes { hr = m_pEffect->Pass( iPass );