Difference between revisions of "DMX"

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'''DMX''' (Data Model eXchange) stores a Datamodel object, encoded in either [[W:Binary file|binary]] or ASCII (KeyValues2). The SDK tool '''dmxconvert''' (available in [[Source Filmmaker]] only) can convert a DMX between the two formats.
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'''DMX''' (Data Model eXchange) stores a Datamodel object, encoded in either [[W:Binary file|binary]] or ASCII. The SDK tool '''dmxconvert''' (available in [[Source Filmmaker]] only) can convert a DMX between the two formats.
  
The internal structure ("format") of a DMX is defined by the user.
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The internal structure or "format" of a DMX is defined by the user.
  
 
== Header ==
 
== Header ==

Revision as of 14:02, 18 December 2012

DMX (Data Model eXchange) stores a Datamodel object, encoded in either binary or ASCII. The SDK tool dmxconvert (available in Source Filmmaker only) can convert a DMX between the two formats.

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.

Tip.png Tip: When hand-editing you can generate IDs for new elements with this website (or with guidgen itself, if you have the Windows SDK installed).
Bug.png Bug: It is not currently possible to serialise a Datamodel to KV2 with the SDK.

Binary

Compared to KeyValues2, binary DMX is:

  1. Small, especially when storing large ints or accurate floats
  2. Fast, as values do not have to be converted to or from human-readable characters
  3. Robust, since it does not have to worry about delimiters, line breaks or unclosed quote blocks
  4. 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

See DMX model for technical details.

Created by vsdmxio, which only available publicly as a Maya plugin (sourcesdk/maya/2009/plug-ins/valveSource/). Some editing options are available with the Source 2009 SDK tool dmxedit however, including export to OBJ (unweighted, no animations).

There are two versions of DMX Model floating about at the moment: 1 (Orange Box) and 18 (Alien Swarm). Each build of Studiomdl only supports one version! Dmxconvert can apparently upgrade old files to the latest version, but we don't have it.

Using dmxedit

  • Create an empty file called vs.lua in the SDK binaries folder. This is probably meant to contain commands that are executed every time you run the tool.
  • You must then create a LUA file containing the actions you want to perform. Here is a simple example that exports to OBJ:
Load( "<path_to_dmx>" )
Save("<export_path>.obj")
  • Perform dmxedit -nop4 myfile.lua to run the script.

If export a mesh DMX to OBJ you will get a single file. If you export a morph DMX you will get one OBJ for each flex animation that was in the file. If you chose an animation you will get nothing; it seems that dmxedit doesn't support animations.

Source Filmmaker sessions

See Source Filmmaker.

Programming

Handling DMX files has many similarities to handling KeyValues. The big architectural differences are that:

  • Where KVs had keys, Datamodel has CDmxElement objects containing CDmxAttribute (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.

There are 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.

Note.png Note: Strings are CUtlString objects, not char!

Creating

Bug.png Bug: The SerializeDMX() overload that requires a file path does not work. You must serialize to a buffer then write out manually.
#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. To do: Elegant solution to arrays.

#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.