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UUSL GBuffer Structure

G-buffer is a series of textures where all the visible information is written: albedo color, normals, lightmap, etc. G-buffer is used for deferred rendering pipeline.

UUSL has a handy GBuffer structure to fill it in the shader's code.

Notice
Since main workflow in UNIGINE is metalness, it has different structure of G-buffer than specular workflow has.

GBuffer Textures#

GBuffer has the following set of textures:

Texture name Type Description
Albedo RGBA8 RGB - albedo value.
A - occlusion value.
Shading RGBA8 R - metalness value.
G - F0 (specular) value.
B - translucent value.
A - microfiber value.
Normal RGBA8 RGB - normal value.
A - roughness value.
Velocity RG16F RG - pixel displacement value (XY coordinates).
Material Mask R32U R - material mask value.
Lightmap RG11B10F RGB - lightmap value.
Geodetic Flat Position RGBA32F RGBA - lightmap value.
Features RGBA8 R - bevel value.
G - cavity mask.
B - convexity mask.
Depth Patch RG32F R - fragment depth.
G - geometry depth.

Channels of these textures fill the corresponding fields of the GBuffer and GBufferSpecular structures.

GBuffer Structures#

struct GBuffer

The GBuffer structure has a set of textures, the channels of which fill in the specified fields.

Fields

  • float3 albedo - Albedo color value.
  • float transparent - Alpha value for Alpha Test and Alpha Blend materials.
  • float metalness - Metalness value.
  • float roughness - Roughness value.
  • float f0 - Specular value.
  • float microfiber - Microfiber value.
  • float3 normal - Packed GBuffer normal in view space.
  • float translucent - Translucent value.
  • float2 velocity - Pixel displacement value (XY coordinates).
  • float3 lightmap - RGB - lightmap value.
  • float occlusion - Occlusion value.
  • float bevel - Bevel value.
  • float2 curvature - Curvature values: R - cavity, G - convexity.
  • int material_mask - Material mask value.
  • float depth_patch - Fragment depth.

struct GBufferSpecular

The Specular GBuffer structure has a set of textures, the channels of which fill in the specified fields. To convert Specular GBuffer to Metalness GBuffer, use the specularToMetalness() function.

Fields

  • float3 diffuse - Diffuse surface color.
  • float transparent - Alpha value for Alpha Test and Alpha Blend materials.
  • float3 specular - Specular surface color.
  • float gloss - Surface glossiness.
  • float microfiber - Microfiber value.
  • float3 normal - Packed GBuffer normal in view space.
  • float translucent - Translucent value.
  • float2 velocity - Pixel displacement value (XY coordinates).
  • float3 lightmap - RGB - lightmap value.
  • float occlusion - Occlusion value.
  • float bevel - Bevel value.
  • float2 curvature - Curvature values: R - cavity, G - convexity.
  • int material_mask - Material mask value.
  • float depth_patch - Fragment depth.

GBuffer Functions#

GBuffer GBufferDefault ( ) #

Default constructor for GBuffer structure for metalness workflow. It creates an instance with default (not null) values.

Return value

GBuffer structure with default (not null) values.

GBufferSpecular GBufferSpecularDefault ( ) #

Constructor for GBuffferSpecular structure for specular workflow. It creates an instance with default (not null) values.

Return value

GBufferSpecular structure with default (not null) values.

GBuffer specularToMetalness ( GBufferSpecular gbuffer ) #

Converts given specular GBufferSpecular to metalness Gbuffer.

Arguments

  • GBufferSpecular gbuffer - Specular GBufferSpecular instance to be converted.

Return value

Metalness Gbuffer instance.

void setGBuffer ( GBuffer gbuffer ) #

Sets GBuffer values by using corresponding values of given GBuffer instance.

Arguments

  • GBuffer gbuffer - GBuffer instance with necessary values to be set.

void setGBuffer ( GBufferSpecular gbuffer ) #

Sets GBuffer values by using corresponding values of given GBufferSpecular instance.
Inside this method specularToMetalness() is called.

Arguments

  • GBufferSpecular gbuffer - GBufferSpecular instance with necessary values to be set.

void loadGBufferAlbedo ( inout GBuffer gbuffer, Texture2D TEX_ALBEDO, float2 uv ) #

Loads albedo texture values (albedo color and occlusion) to GBuffer.

Arguments

  • inout GBuffer gbuffer - Gbuffer structure. Values will be written in it.
  • Texture2D TEX_ALBEDO - Albedo texture.
  • float2 uv - UV coordinates.

void loadGBufferShading ( inout GBuffer gbuffer, Texture2D TEX_SHADING, float2 uv ) #

Loads shading texture values (metalness, f0, translucence, microfiber) to GBuffer.

Arguments

  • inout GBuffer gbuffer - Gbuffer structure. Values will be written in it.
  • Texture2D TEX_SHADING - Shading texture.
  • float2 uv - UV coordinates.

void loadGBufferNormal ( inout GBuffer gbuffer, Texture2D TEX_NORMAL, float2 uv ) #

Loads normal texture values (normal and roughness) to GBuffer.

Arguments

  • inout GBuffer gbuffer - Gbuffer structure. Values will be written in it.
  • Texture2D TEX_NORMAL - Normal texture.
  • float2 uv - UV coordinates.

float3 unpackGBufferNormal ( float3 normal ) #

Returns the normal unit vector into which the RGB normal is unpacked.

Arguments

  • float3 normal - RGB8 normal.

Return value

Normal unit vector.

float3 unpackGBufferNormal ( float4 normal ) #

Returns the normal unit vector into which the RGB normal is unpacked.

Arguments

  • float4 normal

Return value

Normal unit vector.

float3 packGBufferNormal ( float3 normal ) #

Returns the RGB8 vector, into which the normal unit vector is packed.

Arguments

  • float3 normal - Normal unit vector.

Return value

RGB8 normal.

void gbufferSRGB ( GBuffer gbuffer ) #

Apples sRGB correction to albedo and F0.

Arguments

  • GBuffer gbuffer - GBuffer structure.

Usage Example#

Defining the GBuffer Structure#

To use GBuffer structure in your shader's code, you should define and initialize the GBuffer structure by using its constructors. For metalness worlkflow use GBufferDefault() constructor (for specular workflow you should use GBufferSpecular structure and GBufferSpecularDefault() constructor respectively).

The following example shows the way of creating GBuffer structure for both workflows by using #ifdef #else #endif preprocessor statements.

UUSL
/* ... */
	#ifdef METALNESS
		GBuffer gbuffer = GBufferDefault();
		#define GBUFFER gbuffer
	#else
		GBufferSpecular gbuffer_s = GBufferSpecularDefault();
		#define GBUFFER gbuffer_s
	#endif
/* ... */
Notice
Defining the GBUFFER with #define directive is handy to get access to GBuffer structure, no matter what type of the workflow is used.

Filling the GBuffer Structure#

After defining and initializing the GBuffer structure (like in an example above), you can easily fill the GBuffer's fields. You can fill the specific channel of the GBuffer texture.

UUSL
/* ... */
	#ifdef METALNESS
		GBUFFER.albedo		= color.rgb;
		GBUFFER.metalness	= shading.r;
		GBUFFER.roughness	= shading.g;
		
	#else
		GBUFFER.diffuse		= color.rgb;
		GBUFFER.specular	= shading.rgb;
		GBUFFER.gloss		= shading.a;
		GBUFFER.microfiber	= m_microfiber;
		
	#endif
/* ... */

Loading Textures to GBuffer Structure#

Another way of filling the GBuffer structure is using GBuffer functions for textures loading.

In case of changing GBuffer structure fields, these loading functions will perform the same function, preventing possible errors during migration to another UNIGINE Engine version.

UUSL
// initialize textures
/* ... */
INIT_TEXTURE(1,TEX_NORMAL)
INIT_TEXTURE(2,TEX_ALBEDO)
INIT_TEXTURE(3,TEX_SHADING)
/* ... */

/* ... */
GBuffer gbuffer = GBufferDefault();
loadGBufferAlbedo(gbuffer, TEXTURE_OUT(TEX_ALBEDO),uv);
loadGBufferShading(gbuffer, TEXTURE_OUT(TEX_SHADING),uv);
loadGBufferNormal(gbuffer, TEXTURE_OUT(TEX_NORMAL),uv);
/* ... */
Last update: 2022-03-05
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