UUSL Semantics

Redefined UUSL semantics allows you to create unified input\output shader structures for both graphics APIs.

Vertex shader semantics contain necessary input and output data for shader. You should initialize variables first and then use them.

UUSL	OpenGL	Direct3D	Description
INIT_ATTRIBUTE(TYPE,NUM,SEMANTICS)	in TYPE s_attribute_ ## NUM;	TYPE attribute_ ## NUM : SEMANTICS;	Adds a semantic to a vertex shader variable.
INIT_OUT(TYPE,NUM)	out TYPE s_texcoord_ ## NUM;	TYPE data_ ## NUM : TEXCOORD ## NUM;	Adds an output data semantic.
INIT_POSITION	-	float4 position : SV_POSITION;	Adds a position system-value semantic.
INIT_INSTANCE	-	uint instance : SV_INSTANCEID;	Adds a per-instance identifier system-value semantic.
INIT_VERTEX_ID	-	uint vertex_id: SV_VertexID	Adds a per-vertex identifier.

Here is an example of vertex shader input and output structures:

UUSL

// Input vertex data
STRUCT(VERTEX_IN)
	INIT_ATTRIBUTE(float4,0,POSITION)	// Vertex position
	INIT_ATTRIBUTE(float4,1,TEXCOORD0)	// Vertex texcoord (uv)
	INIT_ATTRIBUTE(float4,2,TEXCOORD1)	// Vertex basis tangent
	INIT_ATTRIBUTE(float4,3,TEXCOORD2)	// Vertex color
END

// Our output vertex data
STRUCT(VERTEX_OUT)
	INIT_POSITION		// Out projected position
	INIT_OUT(float4,0)	// Texcoord (uv)
	INIT_OUT(float3,1)	// Vertex direction
END

Use the following pre-defined variables to use the input\output vertex shader semantics:

UUSL	OpenGL	Direct3D	Description
IN_INSTANCE	gl_InstanceID	input.instance	An input per-instance identifier system-value variable.
IN_ATTRIBUTE(NUM)	s_attribute_ ## NUM	input.attribute_ ## NUM	An input shader variable.
IN_VERTEX_ID	gl_VertexID	input.vertex_id	An input per-vertex identifier.
OUT_DATA(NUM)	s_texcoord_ ## NUM	output.data_ ## NUM	An output texture coordinates variable.
OUT_POSITION	gl_Position	output.position	An output position system-value variable.

Fragment shader semantics contain necessary input and output data for shader. You should initialize variables first and then use them.

UUSL	OpenGL	Direct3D	Description
INIT_IN(TYPE,NUM)	in TYPE s_texcoord_ ## NUM;	TYPE data_ ## NUM : TEXCOORD ## NUM;	Adds an input texture coordinates semantic.
INIT_COLOR(TYPE)	out TYPE s_frag_color;	TYPE color : SV_TARGET;	Add an output diffuse or specular color semantic (single RT).
INIT_DEPTH	-	float depth : SV_DEPTH;	Add an output depth system-value semantic.
INIT_MRT(TYPE,NUM)	out TYPE s_frag_data_ ## NUM;	TYPE color_ ## NUM : SV_TARGET ## NUM;	Add an output color system-value semantic (some RTs).
INIT_FRONTFACE	---	bool frontface : SV_ISFRONTFACE;	Adds an input semantic indicates primitive face (frontface or not).

To use the variables in the code, use the following variables:

UUSL	OpenGL	Direct3D	Description
IN_POSITION	gl_FragCoord	input.position	An input position value.
IN_DATA(NUM)	s_texcoord_ ## NUM	input.data_ ## NUM	An input texture coordinates variable.
IN_FRONTFACE	!gl_FrontFacing	input.frontface	Floating-point scalar that indicates a back-facing primitive. A negative value faces backwards, while a positive value faces the camera.
OUT_COLOR	s_frag_color	output.color	An output color value (single RT).
OUT_DEPTH	gl_FragDepth	output.depth	An output depth value.
OUT_MRT(NUM)	out TYPE s_frag_data_ ## NUM;	output.color_ ## NUM	An output color value for MRTs.

Here is a simple example of using the variable in the main function of the shader:

USUL

MAIN_FRAG_BEGIN(FRAGMENT_IN)
	
	float4 texcoord = IN_DATA(0);

	/* ... other code ... */
MAIN_FRAG_END

UUSL	OpenGL	Direct3D	Description
INIT_GEOM_IN(TYPE,NUM)	in TYPE s_geom_texcoord_ ## NUM[];	TYPE data_ ## NUM : TEXCOORD ## NUM;	Add an input texture coordinates semantic for the geometry-shader stage.
INIT_GEOM_OUT(TYPE,NUM)	out TYPE s_geom_texcoord_ ## NUM;	TYPE data_ ## NUM : TEXCOORD ## NUM;	Add an output texture coordinates semantic for the geometry-shader stage.

UUSL	OpenGL	Direct3D	Description
IN_GEOM_DATA(NUM,INDEX)	s_geom_texcoord_ ## NUM ## [INDEX]	input[INDEX].data_ ## NUM	An input texture coordinates value.
IN_GEOM_POSITION(INDEX)	gl_in[INDEX].gl_Position	input[INDEX].position	An input position value.
OUT_GEOM_DATA(NUM)	s_geom_texcoord_ ## NUM	output.data_ ## NUM	An output texture coordinates value.
TRIANGLE_IN	triangles	triangle	Input primitive type: triangle list or triangle strip.
TRIANGLE_OUT	triangle_strip	TriangleStream	Output primitive type: a sequence of triangle primitives
LINE_IN	lines	line	Input primitive type: line.
LINE_OUT	line_strip	LineStream	Output primitive type: a sequence of line primitives

Unified shader semantics allows you to create single structure for both vertex and fragment shaders. It facilitates the work with vertex and fragment shaders input/output structure by using single structure for both shaders: this structure will be output for vertex shader and input for fragment shader respectively.

You can write vertex and fragment shader in a single file with .shader extension. In this case, in the material you should specify this .shader file for both shader stages.

Source code (XML)

BaseMaterial <texture_prefix=tex var_prefix=var>
{
	// ...

	Pass auxiliary if [auxiliary]
	{
		Vertex = "core/materials/base/objects/mesh/shaders/auxiliary/auxiliary.shader"
		Fragment = "core/materials/base/objects/mesh/shaders/auxiliary/auxiliary.shader"
	}

	// ..
}

UUSL	VERTEX	FRAGMENT	Description
INIT_DATA(TYPE,NUM,NAME)	INIT_OUT(TYPE,NUM) \ #define NAME GET_DATA(NUM)	INIT_IN(TYPE,NUM) \ #define NAME GET_DATA(NUM)	Data initialization.
GET_DATA(V)	OUT_DATA(V)	IN_DATA(V)	Helper for getting/setting data by using data name.

IF statement#

There is also the IF_DATA(NAME) statement to execute an operation if the data is not null.

UUSL	VERTEX	FRAGMENT	Description
IF_DATA(NAME)	#ifdef NAME	#ifdef NAME	Opening IF conditional statement.
ENDIF	#endif	#endif	Closing IF conditional statement.

Here is a code snippet of shader, where the shader's IF statement is used.

UUSL

//input struct
STRUCT(FRAGMENT_IN)
/* ... */
	#ifdef ALPHA_FADE && USE_ALPHA_FADE
		INIT_DATA(float,1,DATA_ALPHA_FADE)
	#endif
/* ... */
END

//main functions
MAIN_FRAG_BEGIN(FRAGMENT_IN)
/* ... */
	IF_DATA(DATA_ALPHA_FADE)
		//code to execute if the data is not null
		alphaFadeDiscard(DATA_ALPHA_FADE,IN_POSITION.xy);
	ENDIF
/* ... */
MAIN_FRAG_END

In This Article:

Vertex Shader Semantics#

Fragment Shader Semantics#

Geometry Shader Semantics#

Unified Shader Semantics#

IF statement#