着色器构造

d3d11.dll对外着色器提供的结构体分别为：

• gs_vertex_shader（device_vertexshader_create）
• gs_pixel_shader （device_pixelshader_create）

gs_shader_t *device_vertexshader_create(gs_device_t *device,
                    const char *shader_string,
                    const char *file, char **error_string)
{
    return new gs_vertex_shader(device, file, shader_string);
}
gs_shader_t *device_pixelshader_create(gs_device_t *device,
                       const char *shader_string,
                       const char *file, char **error_string)
{
    return new gs_pixel_shader(device, file, shader_string);
}

无论是gs_vertex_shader还是gs_pixel_shader，其核心是通过ShaderProcessor类处理着色器。

struct ShaderParser : shader_parser {
    inline ShaderParser() { shader_parser_init(this); }
    inline ~ShaderParser() { shader_parser_free(this); }
};

struct ShaderProcessor {
    gs_device_t *device;
    ShaderParser parser;

    void BuildInputLayout(vector<D3D11_INPUT_ELEMENT_DESC> &inputs);
    void BuildParams(vector<gs_shader_param> &params);
    void BuildSamplers(vector<unique_ptr<ShaderSampler>> &samplers);
    void BuildString(string &outputString);

    void Process(const char *shader_string, const char *file);
    inline ShaderProcessor(gs_device_t *device) : device(device) {}
};

过程如下：

gs_vertex_shader::gs_vertex_shader(gs_device_t *device, const char *file,
                   const char *shaderString)
    : gs_shader(device, gs_type::gs_vertex_shader, GS_SHADER_VERTEX),
      hasNormals(false),
      hasColors(false),
      hasTangents(false),
      nTexUnits(0)
{
    ShaderProcessor processor(device);
    ComPtr<ID3D10Blob> shaderBlob;
    string outputString;
    HRESULT hr;

    //词法分析
    processor.Process(shaderString, file);

    //生成最终的HLSL脚本
    processor.BuildString(outputString);

    processor.BuildParams(params);    //参数
    processor.BuildInputLayout(layoutData);//布局
    GetBuffersExpected(layoutData);
    BuildConstantBuffer(); //常量参数

    //编译
    Compile(outputString.c_str(), file, "vs_4_0", shaderBlob.Assign());

    data.resize(shaderBlob->GetBufferSize());
    memcpy(&data[0], shaderBlob->GetBufferPointer(), data.size());

    hr = device->device->CreateVertexShader(data.data(), data.size(), NULL,shader.Assign());

    const UINT layoutSize = (UINT)layoutData.size();
    if (layoutSize > 0) {
        hr = device->device->CreateInputLayout(layoutData.data(),
                               (UINT)layoutSize,
                               data.data(), data.size(),
                               layout.Assign());
    }

    viewProj = gs_shader_get_param_by_name(this, "ViewProj");
    world = gs_shader_get_param_by_name(this, "World");
}