Shader models for OpenGL.md

Shader models for OpenGL

With MojoShader the available shader models for OpenGL platforms were vs_2_0, ps_2_0 and vs_3_0, ps_3_0. Those are still available in ShaderConductor, the target GLSL version is identical, in order to support the same hardware as MojoShader did.
Additionally, all the shader models currently available in DirectX can now also be used with OpenGL. The target OpenGL/GLSL versions are chosen automatically, trying to closely match feature levels between DirectX and OpenGL.

If this default mapping is not satisfactory, conditional code can still be used. ESSL is available as an additional define when targeting mobile platforms (Android, iOS)

#if ESSL
    #define VS_SHADERMODEL vs_4_0
    #define PS_SHADERMODEL ps_4_0
#else
    #define VS_SHADERMODEL vs_5_0
    #define PS_SHADERMODEL ps_5_0
#endif

The following table shows how shader models are mapped to GLSL and OpenGL versions, as well as the available shader stages.

Shader model	GLSL (desktop)	ESSL (mobile)	OpenGL (desktop)	OpenGL ES (mobile)	Shader stages (desktop)	Shader stages (mobile)
vs_2_0, ps_2_0 vs_3_0, ps_3_0 vs_4_0_level_9_1, ps_4_0_level_9_1 vs_4_0_level_9_2, ps_4_0_level_9_2 vs_4_0_level_9_3, ps_4_0_level_9_3	110	100	2.0	2.0
vs_4_0, ps_4_0 vs_4_1, ps_4_1	330	300 es	3.3 + SSO*	3.0 + SSO*	GS
vs_5_0, ps_5_0	430	320 es	4.3	3.2	GS, TESS, CS	GS, TESS, CS

* SSO: requires ARB_separate_shader_objects extension.

Shader stages

• GS: Geometry shader
• TESS: Tessellation shader (Hull and Domain)
• CS: Compute shader