[DX12] Allocate, assign SRV and bind descriptor heap

dx12_descriptor_heap_manager.cpp

int DeviceManDX12::AssignDescriptorHeap(int numRequired)
{
	if (numAssignedSrvs + numRequired > maxSrvs) {
		assert(0);
		return -1;
	}
	int head = numAssignedSrvs;
	numAssignedSrvs = numAssignedSrvs + numRequired;
	return head;
}

void DeviceManDX12::AssignSRV(int descriptorHeapIndex, ComPtr<ID3D12Resource> res)
{
	D3D12_CPU_DESCRIPTOR_HANDLE ptr = srvHeap->GetCPUDescriptorHandleForHeapStart();
	ptr.ptr += device->GetDescriptorHandleIncrementSize(D3D12_DESCRIPTOR_HEAP_TYPE_CBV_SRV_UAV) * descriptorHeapIndex;
	device->CreateShaderResourceView(res.Get(), nullptr, ptr);
}

void DeviceManDX12::SetAssignedDescriptorHeap(int descriptorHeapIndex)
{
	ID3D12DescriptorHeap* ppHeaps[] = { srvHeap.Get() };
	deviceMan.GetCommandList()->SetDescriptorHeaps(_countof(ppHeaps), ppHeaps);
	D3D12_GPU_DESCRIPTOR_HANDLE addr = srvHeap->GetGPUDescriptorHandleForHeapStart();
	addr.ptr += descriptorHeapIndex * device->GetDescriptorHandleIncrementSize(D3D12_DESCRIPTOR_HEAP_TYPE_CBV_SRV_UAV);
	deviceMan.GetCommandList()->SetGraphicsRootDescriptorTable(0, addr);
}