OBS Shading Language

OBS Shading Language (OBS-SL)

The baseline for the shader language libOBS uses is HLSL, for which you can find documentation here. libOBS modifies this so it works across all of its supported graphics APIs, sacrificing functionality and versatility for compatibility. As a result, some effects that would be possible with ease in GLSL or HLSL directly do not work in libOBS's shader language. For the sake of all future documentation, the langauge will be referred to as OBS-SL, since it mixes and matches many different langauge constructs into one.

Data

Similar to HLSL, OBS-SL supports storage, transfer and modification of data.

Storage Specifiers

Storage specifiers seem to only be used by the OpenGL backend.

Name	DirectX	OpenGL	Notes
uniform		uniform
const		const
inout		inout
out		out

Types

Name	DirectX	OpenGL
bool	bool	bool
float	float	float
float2	float2	vec2
float3	float3	vec3
float4	float4	vec4
int	int	int
int2	int2	ivec2
int3	int3	ivec3
int4	int4	ivec4
string	string	string
float3x3	float3x3	mat3x3
float3x4	float3x4	mat3x4
float4x4	float4x4	mat4x4
texture2d	Texture2D	sampler2D
texture3d	Texture3D	sampler3D
texture_cube	TextureCube	samplerCube
texture_rect	N/A	sampler2DRect
sampler_state	SamplerState	Metadata only

Arrays

At the time of writing this, Arrays are only supported when DirectX is being used by libOBS. The patch to make it available in OpenGL was retracted at the request of the current OBS Project team.

Keywords

A limited subset of keywords are supported, other keywords may work if they match across both langauges.

Name	DirectX	OpenGL
POSITION	SV_Position	gl_FragCoord
TARGET	SV_Target	N/A
VERTEXID	SV_VertexID	uint(gl_VertexID)

Input/Output Semantics

A limited subset of semantics are supported, other keywords will not work.

Name	DirectX	OpenGL	Notes
POSITION	SV_Position	Metadata only	Provided as float32[4]
NORMAL	NORMAL	Metadata only	Provided as float32[4]
COLOR	COLOR	Metadata only	Provided as uint8_unorm[4]
TANGENT	TANGENT	Metadata only	Provided as float32[4]
TEXCOORD	TEXCOORD	Metadata only	Either float32, float32[2] or float32[4].
VERTEXID	VERTEXID	Metadata only