Xflow syntax change

Xflow program flows are hard to read:

<data compute="position = xflow.morph(position, posAdd2, weight2)" >
	<data compute="position = xflow.morph(position, posAdd1, weight1)" >
		<data compute="posAdd1 = xflow.sub(blend1Pos, position)" >
			<data compute="posAdd2 = xflow.sub(blend2Pos, position)" >
				<data src="blend-mesh.xml#mesh"></data>
				<float name="weight1" >1</float>
				<float name="weight2" >1</float>
			</data>
		</data>
	</data>
</data>

We can introduce the <dataflow> element to make Xflow more readable:

<dataflow>
	<data src="blend-mesh.xml#mesh"></data>
	<float name="weight1" >1</float>
	<float name="weight2" >1</float>
	<compute>
		posAdd1 = xflow.sub(position, blend1Pos);
		position = xflow.morph(position, posAdd1, weight1);
		posAdd2 = xflow.sub(position, blend2Pos);
		position = xflow.morph(position, posAdd2, weight2);
	</compute>
</dataflow>

Content of the <dataflow> element is evaluate from top to bottom. Every <compute> element can access data declared in previous siblings. Each <compute> includes a list of statements as previously found in the compute attribute, separated by semicolons. It is possible to have multiple <compute> elements inside a <dataflow>.

Here a more complicated example with prototypes:

<proto id="doubleBlend" filter="keep(result)" compute="result = xflow.morph(value, valueAdd2, weight2)">
	<data compute="value = xflow.morph(value, valueAdd1, weight1)">
		<data compute="valueAdd2 = xflow.sub(blend2, value)">
			<data compute="valueAdd1 = xflow.sub(blend1, value)">
				<float3 param name="value"></float3>
				<float3 param name="blend1"></float3>
				<float3 param name="blend2"></float3>
				<float param name="weight1"></float>
				<float param name="weight2"></float>
			</data>
		</data>
	</data>
</proto>

<proto id="morphShape" filter="keep(position, normal)">
	<data filter="rename({position : result})" proto="#doubleBlend">
		<data filter="rename({value: position, blend1: blend1Pos, blend2: blend2Pos})">
			<float3 param name="position"></float3>
			<float3 param name="blend1Pos"></float3>
			<float3 param name="blend2Pos"></float3>
			<float param name="weight1">0.5</float>
			<float param name="weight2">0.5</float>
		</data>
	</data>
	<data filter="rename({normal : result})" proto="#doubleBlend">
		<data filter="rename({value: normal, blend1: blend1Normal, blend2: blend2Normal})">
			<float3 param name="normal"></float3>
			<float3 param name="blend1Normal"></float3>
			<float3 param name="blend2Normal"></float3>
			<float param name="weight1">0.5</float>
			<float param name="weight2">0.5</float>
		</data>
	</data>
</proto>

<mesh type="triangles" proto="#morphShape" >
   <data src="blend-mesh.xml#mesh" ></data>
   <float name="weight1" >0.5</float>
   <float name="weight2" >0.5</float>
</mesh>

And here the same example using <dataflow>. We can drop <proto> and reuse <dataflow> to declare reusable computation components.

<dataflow id="doubleBlend" out="result">
	<float3 param name="value"></float3>
	<float3 param name="blend1"></float3>
	<float3 param name="blend2"></float3>
	<float  param name="weight1"></float>
	<float  param name="weight2"></float>
	<compute>
		add1 = xflow.sub(value, blend1);
		add2 = xflow.sub(value, blend2);
		result = xflow.morph(position, posAdd1, weight1);
		result = xflow.morph(result, posAdd2, weight2);
	</compute>		
</dataflow>

<dataflow id="morphShape" out="position, normal" >
	<float3 param name="position"></float3>
	<float3 param name="blend1Pos"></float3>
	<float3 param name="blend2Pos"></float3>
	<float3 param name="normal"></float3>
	<float3 param name="blend1Normal"></float3>
	<float3 param name="blend2Normal"></float3>
	<float  param name="weight1">0.5</float>
	<float  param name="weight2">0.5</float>
	<compute>
		position = dataflow['#doubleBlend'](position, blend1Pos, blend2Pos, weight1, weight2);
		normal = dataflow['#doubleBlend'](normal, blend1Normal, blend2Normal, weight1, weight2);
	</compute>		
</dataflow>

<mesh type="triangles" compute="[#morphShape]" >
   <data src="blend-mesh.xml#mesh" ></data>
   <float name="weight1" >0.5</float>
   <float name="weight2" >0.5</float>
</mesh>