根签名 root signature
1
2
3
4
| root signature只有64 DWORD的空间.
Descriptor tables cost 1 DWORD each.
Root constants cost 1 DWORD each, since they are 32 - bit values
Root descriptors(64 - bit GPU virtual addresses) cost 2 DWORDs each.
|
微软链接
Constants绑定有3种方法
方法一:Root constants
D3D12_ROOT_PARAMETER_TYPE_32BIT_CONSTANTS
dxd12的封装函数是InitAsConstants.
draw的时候是:SetGraphicsRoot32BitConstants
1
2
3
4
5
6
7
8
9
10
| CD3DX12_ROOT_PARAMETER slotRootParameter[1];
slotRootParameter[0].InitAsConstants(16, 0);//绑定一个4x4的矩阵
XMFLOAT4X4 m;
XMStoreFloat4x4(&m, XMMatrixTranspose(worldViewProj)); // 转置矩阵
mCommandList->SetGraphicsRoot32BitConstants(
0, // 根参数的索引
sizeof(XMFLOAT4X4) / sizeof(float), // 要传递的32位浮点数的数量
&m, // 指向常量的指针
0 // 常量缓冲区中的偏移量（以32位浮点数为单位）
);
|
方法二:Root descriptors
直接绑定到根签名下,一般矩阵使用这种形式.
D3D12_ROOT_PARAMETER_TYPE_CBV
1
2
3
4
5
| CD3DX12_ROOT_PARAMETER slotRootParameter[1];
slotRootParameter[0].InitAsConstantBufferView(0);
//draw
D3D12_GPU_VIRTUAL_ADDRESS cbAddress = mObjectCB->Resource()->GetGPUVirtualAddress();
mCommandList->SetGraphicsRootConstantBufferView(0, cbAddress);
|
方法三:Descriptor tables
使用根标识表绑定
1
2
3
4
5
6
7
8
| CD3DX12_ROOT_PARAMETER slotRootParameter[1];
CD3DX12_DESCRIPTOR_RANGE cbvTable;
cbvTable.Init(D3D12_DESCRIPTOR_RANGE_TYPE_CBV, 1, 0);
slotRootParameter[0].InitAsDescriptorTable(1, &cbvTable);
//draw
ID3D12DescriptorHeap* descriptorHeaps[] = {mCbvHeap.Get()};
mCommandList->SetDescriptorHeaps(_countof(descriptorHeaps), descriptorHeaps);
mCommandList->SetGraphicsRootDescriptorTable(0, mCbvHeap->GetGPUDescriptorHandleForHeapStart());
|