Unigine Language Object Notation (ULON)

ULON (Unigine Language Object Notation) is a universal format used in UNIGINE to describe complex structures similar to classes in Object-Oriented Programming. Landscape Terrain brushes as well as some of UNIGINE built-in materials are described using ULON.

The Engine supports loading and parsing files containing ULON-declarations, but does not support saving ULON-based structures to a file as such declarations are treated more like source code.

ULON Description Example

See Also#

The basic element (building brick) of ULON is called a node. Each node has a type, a name, and a value.

The following construct is used to declare a node:

Both node name and type are written as strings:

• either a quoted string with standard escape characters,
• or a bare word, beginning with a lower case letter, containing only letters, digits, and underscores "_".

Here is an example:

"Node Type" "node name" = node_value
NodeType node_name1 = node_value

Node declarations can be nested, thus forming a hierarchy. So a node can have a parent and an unlimited number children.

Node parent
{
	Node child_0
	Node child_1
	{
		Node child_2
		Node child_3
	}
}

ULON node values can be of the following types:

• Boolean
  Node my_node = true
• Integer number
  Node my_node = 1234
• Floating-point number
  Node my_node = 3.1459
• String
  
  • Quoted string with standard escape characters:
    Node node = "word word"
  • Bare word, beginning with a lower case letter, containing only letters, digits, and underscores "_":
    Node node = word1_word2
  • Heredoc string enclosed in #{ ... #}. This type can be used for code fragments (e.g., shader code embedded into material description):
    Node my_node = #{C++ C# USC HLSL USSL#}
• Array containing a finite number of integer, float, and string elements
  Node my_node = [100, 0.2, str str "str str str", #{vec4 asd = vec4_zero;#}]
  This array has the following 6 elements:
  • 100
  • 0.2
  • str
  • str
  • str str str
  • vec4 asd = vec4_zero;

ULON argument is a name - value pair (name = value). Arguments are additional parameters that can be associated with ULON nodes and used for various purposes (e.g. to define a tooltip or a title for a material parameter declaration). Arguments are enclosed in angle brackets < > and can be separated using "\t","\n","\r", as well as commas and spaces.

Example:

For each node a logical condition can be specified, if the condition fails the ULON node with all its children is ignored. Thus you can dynamically build the hierarchy of ULON nodes with a great degree of flexibility. This can be useful when the contents of the node depends on certain parameters, e.g. a shader to be used is defined by the rendering pass.

Conditions are specified after the node's name, starting with the if keyword, the condition itself is enclosed in brackets [ ... ].

Condition of the parent node is added to the condition of the child: (parent_conditon) && (child_conditon)

Example:

Node parent if[var1 == 10 || var1 == 5]
{
	Node child_0  if[var2 == 3]
	Node child_1  if[var2 == 4]
	{
		Node child_2 if[var3 != 11]
		Node child_3 if[var3 != 25]
	}
}

The resulting conditions for each node are as follows:

• parent condition: (var1 == 10 || var1 == 5)
• child_0 condition: (var1 == 10 || var1 == 5) && (var2 == 3)
• child_1 condition: (var1 == 10 || var1 == 5) && (var2 == 4)
• child_2 condition: (var1 == 10 || var1 == 5) && (var2 == 4) && (var3 != 11)
• child_3 condition: (var1 == 10 || var1 == 5) && (var2 == 4) && (var3 != 25)

Adding comments make object declaration easier to understand, especially if the object is a complex one. The following types of comments are supported:

• single-line comments starting with "//":
  // This is a single-line comment
• multi-line comments enclosed within "/*" and "*/":
  /* This is
  a multi-line
  comment */

Below you can find the example on how to use ULON file format to describe a Scriptable Material (radial blur in this case):

BaseMaterial post_scriptable_blur_radial <preview_hidden=1 var_prefix=var texture_prefix=tex>
{
	// specify an internal texture to be used
	Texture src_color <type=procedural internal=true>

	// define the material's states and parameters available in the Editor
	Group "Blur Radial"
	{
		Int sample_count = 16 <min=1 max=32>
		Slider weight_decay = 0.95 <min=0.1 max=1.0 internal=true>
		Slider radius = 0.2 <min=0.0 max=1.0>
	}

	// define the blur render pass
	Pass render_scriptable_blur_radial
	{
		// write the fragment (pixel) shader in UUSL or HLSL
		Fragment=
		#{
			// default fragment shader include
			#include <core/materials/shaders/render/common.h>

			STRUCT_FRAG_BEGIN
				INIT_COLOR(float4)
			STRUCT_FRAG_END
				
			MAIN_FRAG_BEGIN(FRAGMENT_IN)
	
				// get the UV coordinates in [-0.5; 0.5] range
				float2 offset = IN_UV - float2(0.5f, 0.5f);

				// calculate an offset based on the sample count and the radius
				float inv_sample_count = 1.0f / toFloat(var_sample_count);
				offset *= toFloat2(inv_sample_count * var_radius);

				// get the UV coordinates of the texture
				float2 uv = float2(IN_UV.x, IN_UV.y);

				// sum up texture samples along the line
				OUT_COLOR.rgb = float3_zero;
				loop for (int i = 1; i<=var_sample_count; i++)
				{
					OUT_COLOR.rgb += TEXTURE_BIAS_ZERO(tex_src_color, uv).xyz;
					uv -= offset;
				}

				// normalize the result
				OUT_COLOR = float4(OUT_COLOR.rgb * toFloat3(inv_sample_count), 1.0f);

			MAIN_FRAG_END
		#}
	}

	// the expression in Unigine Script defines a callback
	Expression RENDER_CALLBACK_END_POST_MATERIALS = 
	#{
		// declare the source texture from the screen frame
		Texture source = engine.render.getTemporaryTexture(engine.render_state.getScreenColorTexture());

		// define the source texture from the screen frame
		source.copy(engine.render_state.getScreenColorTexture());

		// set the color source texture to use it in the shader
		setTexture("src_color", source);

		// render the outline result texture to output it to the screen
		renderPassToTexture("render_scriptable_blur_radial", engine.render_state.getScreenColorTexture());

		//release the temporary texture
		engine.render.releaseTemporaryTexture(source);
	#}
}