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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

ULON Description Example

See Also#

Nodes#

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:

ULON Node Declaration

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:
Source code
"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.

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

Values#

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 GLSL 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;

Arguments#

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:

ULON Arguments Declaration

Conditions#

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.

Notice
Conditions are not parsed and executed automatically, processing of conditions is the responsibility of the user of the ULON format (e.g. in case of materials UnigineScript and UUSL are used).
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:

Source code
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)

Comments#

Adding comments make object declaration easier to understand, especially if the object is a complex one. The following type os 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 */

ULON-based Scriptable Material Example#

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

Source Code (ULON)
BaseMaterial post_scriptable_blur_radial <options_hidden=1 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/GLSL
		Fragment=
		#{
			// default fragment shader include
			#include <core/shaders/common/fragment.h>

			MAIN_BEGIN(FRAGMENT_OUT, 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 / to_float(var_sample_count);
				offset *= to_float2(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 * to_float3(inv_sample_count), 1.0f);

			MAIN_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);
	#}
}
Last update: 2021-08-24
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