DMX
DMX (Data Model eXchange) stores a Datamodel object, encoded in either binary or ASCII. The internal structure or "format" of a DMX is defined by the user.
Header
All DMX files start with this header:
<!-- dmx encoding [encoding name] [encoding version] format [format name] [format version] -->
Encodings
KeyValues2
This ASCII encoding is the successor to KeyValues. It's good if you have a small DMX and want it hand-editable.
Binary
Compared to KeyValues2, binary DMX is:
- Small, especially when storing large ints or accurate floats
- Fast, as values do not have to be converted to or from human-readable characters
- Robust, since it does not have to worry about delimiters, line breaks or unclosed quote blocks
- Inscrutable, because it contains native binary data
Binary is good for large DMXes.
See DMX/Binary for a technical description of the encoding.
Formats
These are the formats used by Valve.
Particle System
Created by the Particle Editor and read by the engine, usually with the extension pcf
. There should be no reason to manipulate these yourself.
Model
The DMX model deprecates SMD in and newer. It can be exported by Valve's official Maya plugin (sourcesdk/maya/2009/plug-ins/valveSource/
), the Blender Source Tools and from the 3ds Max pipeline tools in Wall Worm Model Tools.
There are some DMX-related tools in the SDK:
Engine Tools
DMX is widely used to represent data in engine tools. For example, Source Filmmaker save files are stored as DMX, and materials are converted to DMX by Material Editor in order to be edited.
Programming
Handling DMX files has many similarities to handling KeyValues. The big architectural differences are that:
- Where KVs had keys, Datamodel has
CDmxElement
objects containingCDmxAttribute
(which can point to further elements). - There is support for arrays.
- Attribute values are accessed through a single templated function, not lots of different ones.
- Each element can have multiple parents. Each element has a 128-bit ID to support this.
Source API
Source has two DMX APIs: CDmxElement
and CDmElement
. The former is a lightweight implementation designed for use in game code; the latter is designed around the needs of the engine tools and includes heavyweight features like undo levels and element factories. The mod SDK only supports CDmxElement
.
For a full list of attribute types, see the bottom of public\datamodel\dmattributetypes.h
.
CUtlString
objects, not char
!Creating
SerializeDMX()
overload that requires a file path does not work. You must serialize to a buffer then write out manually. [todo tested in?]#include "cbase.h"
#include "dmxloader/dmxloader.h"
#include "dmxloader/dmxelement.h"
CON_COMMAND( dmx_create, "Makes a simple DMX" )
{
DECLARE_DMX_CONTEXT();
CDmxElement* DMX = CreateDmxElement("MyElementTypeName");
DMX->AddAttribute("C++ templates")->SetValue<bool>(true);
DMX->AddAttribute("Hello")->SetValue("world"); // non-templated shortcut for strings
DMX->AddAttribute("An_Array")->GetArrayForEdit<float>().AddToTail(3.141);
CUtlBuffer buf;
SerializeDMX(buf,DMX);
FileHandle_t fh = filesystem->Open("test.dmx","w","DEFAULT_WRITE_PATH");
filesystem->Write(buf.Base(),buf.TellPut(),fh);
filesystem->Close(fh);
}
Iterator
This code will print string, int, float and bool values in the given DMX to the console.
#include "cbase.h"
#include "dmxloader/dmxloader.h"
#include "dmxloader/dmxelement.h"
void IterateDmxElement(CDmxElement* pRoot)
{
for (int i=0;i<pRoot->AttributeCount();i++)
{
CDmxAttribute* pCur = pRoot->GetAttribute(i);
CDmxElement* subElem;
Warning( "%s: ",pCur->GetName() );
switch (pCur->GetType())
{
case AT_ELEMENT:
subElem = pCur->GetValue<CDmxElement*>();
if (subElem)
IterateDmxElement(subElem);
break;
case AT_STRING:
Msg( "STRING | %s\n",pCur->GetValue<CUtlString>().Get() );
break;
case AT_INT:
Msg( "INT | %i\n",pCur->GetValue<int>() );
break;
case AT_FLOAT:
Msg( "FLOAT | %f\n",pCur->GetValue<float>() );
break;
case AT_BOOL:
Msg( "BOOL | %s\n",pCur->GetValue<bool>() ? "true" : "false" );
break;
default:
Msg("Unknown type %i\n",pCur->GetType());
break;
}
}
}
CON_COMMAND(dmx_iterate, "Prints a DMX file to the console")
{
DECLARE_DMX_CONTEXT();
CDmxElement* DMX = (CDmxElement*)DMXAlloc( 50000000 );
if (UnserializeDMX(args[1],"MOD",false,&DMX))
{
IterateDmxElement(DMX);
}
else
Warning("Could not read DMX file %s\n",args[1]);
}
KeyValues2
dmxloader.lib has several "TextDMX" functions that are not referenced in the SDK's headers. Among them are:
bool UnserializeTextDMX(const char* pFilename,CUtlBuffer & buf,CDmxElement** ppRoot); // fails
bool SerializeTextDMX(const char* pFilename,CUtlBuffer & buf,CDmxElement* pRoot); // produces invalid files
They are both underdeveloped. It's possible that only CDmElement
supports KeyValues2.
Third-party libraries
There are currently two other Datamodel/DMX libraries:
- Datamodel.NET (CLR/C#)
- datamodel.py (Python)
- Datamodel-rs (Rust)