High-Level Shader Language Explained

The High-Level Shader Language^[1] or High-Level Shading Language^[2] (HLSL) is a proprietary shading language developed by Microsoft for the Direct3D 9 API to augment the shader assembly language, and went on to become the required shading language for the unified shader model of Direct3D 10 and higher.

HLSL is analogous to the GLSL shading language used with the OpenGL standard. It is very similar to the Nvidia Cg shading language, as it was developed alongside it. Early versions of the two languages were considered identical, only marketed differently.^[3] HLSL shaders can enable profound speed and detail increases as well as many special effects in both 2D and 3D computer graphics.

HLSL programs come in six forms: pixel shaders (fragment in GLSL), vertex shaders, geometry shaders, compute shaders, tessellation shaders (Hull and Domain shaders), and ray tracing shaders (Ray Generation Shaders, Intersection Shaders, Any Hit/Closest Hit/Miss Shaders). A vertex shader is executed for each vertex that is submitted by the application, and is primarily responsible for transforming the vertex from object space to view space, generating texture coordinates, and calculating lighting coefficients such as the vertex's normal, tangent, and bitangent vectors. When a group of vertices (normally 3, to form a triangle) come through the vertex shader, their output position is interpolated to form pixels within its area; this process is known as rasterization.

Optionally, an application using a Direct3D 10/11/12 interface and Direct3D 10/11/12 hardware may also specify a geometry shader. This shader takes as its input some vertices of a primitive (triangle/line/point) and uses this data to generate/degenerate (or tessellate) additional primitives or to change the type of primitives, which are each then sent to the rasterizer.

D3D11.3 and D3D12 introduced Shader Model 5.1^[4] and later 6.0.^[5]

Shader model comparison

GPUs listed are the hardware that first supported the given specifications. Manufacturers generally support all lower shader models through drivers. Note that games may claim to require a certain DirectX version, but don't necessarily require a GPU conforming to the full specification of that version, as developers can use a higher DirectX API version to target lower-Direct3D-spec hardware; for instance DirectX 9 exposes features of DirectX7-level hardware that DirectX7 did not, targeting their fixed-function T&L pipeline.

Pixel shader comparison

Pixel shader version	1.0	1.1	1.21.3^[6]	1.4	2.0^[7]	2.0a^[8]	2.0b^[9]	3.0^[10]	4.0^[11] 4.1^[12] 5.0^[13]
Dependent texture limit	4	4	4	6	8	Unlimited	8	Unlimited	Unlimited
Texture instruction limit	4	4	4	6 * 2	32	Unlimited	Unlimited	Unlimited	Unlimited
Arithmetic instruction limit	8	8	8	8 * 2	64	Unlimited	Unlimited	Unlimited	Unlimited
Position register
Instruction slots	8	8 + 4	8 + 4	(8 + 6) * 2	64 + 32	512	512	≥ 512	≥ 65536
Executed instructions	8	8 + 4	8 + 4	(8 + 6) * 2	64 + 32	512	512	65536	Unlimited
Texture indirections	4	4	4	4	4	Unlimited	4	Unlimited	Unlimited
Interpolated registers	2 + 4	2 + 4	2 + 4	2 + 6	2 + 8	2 + 8	2 + 8	10	32
Instruction predication
Index input registers
Temp registers	2	2 + 4	3 + 4	6	12 to 32	22	32	32	4096
Constant registers	8	8	8	8	32	32	32	224	16×4096
Arbitrary swizzling
Gradient instructions
Loop count register
Face register (2-sided lighting)
Dynamic flow control								(24)	(64)
Bitwise Operators
Native Integers

• PS 1.0 — Unreleased 3dfx Rampage, DirectX 8
• PS 1.1 — GeForce 3, DirectX 8
• PS 1.2 — 3Dlabs Wildcat VP, DirectX 8.1
• PS 1.3 — GeForce 4 Ti, DirectX 8.1
• PS 1.4 — Radeon 8500-9250, Matrox Parhelia, DirectX 8.1
• Shader Model 2.0 — Radeon 9500-9800/X300-X600, DirectX 9
• Shader Model 2.0a — GeForce FX/PCX-optimized model, DirectX 9.0a
• Shader Model 2.0b — Radeon X700-X850 shader model, DirectX 9.0b
• Shader Model 3.0 — Radeon X1000 and GeForce 6, DirectX 9.0c
• Shader Model 4.0 — Radeon HD 2000 and GeForce 8, DirectX 10
• Shader Model 4.1 — Radeon HD 3000 and GeForce 200, DirectX 10.1
• Shader Model 5.0 — Radeon HD 5000 and GeForce 400, DirectX 11
• Shader Model 5.1 — GCN 1+, Fermi+, DirectX 12 (11_0+) with WDDM 2.0
• Shader Model 6.0 — GCN 1+, Kepler+, DirectX 12 (11_0+) with WDDM 2.1
• Shader Model 6.1 — GCN 1+, Kepler+, DirectX 12 (11_0+) with WDDM 2.3
• Shader Model 6.2 — GCN 1+, Kepler+, DirectX 12 (11_0+) with WDDM 2.4
• Shader Model 6.3 — GCN 1+, Kepler+, DirectX 12 (11_0+) with WDDM 2.5
• Shader Model 6.4 — GCN 1+, Kepler+, Skylake+, DirectX 12 (11_0+) with WDDM 2.6
• Shader Model 6.5 — GCN 1+, Kepler+, Skylake+, DirectX 12 (11_0+) with WDDM 2.7
• Shader Model 6.6 — GCN 4+, Maxwell+, DirectX 12 (11_0+) with WDDM 3.0
• Shader Model 6.7 — GCN 4+, Maxwell+, DirectX 12 (12_0+) with WDDM 3.1

"32 + 64" for Executed Instructions means "32 texture instructions and 64 arithmetic instructions."

Vertex shader comparison

Vertex shader version	1.0	1.1^[14] !2.0	2.0a	3.0	4.0 4.1 5.0
of instruction slots	128	128	256	256	≥ 512	≥ 65536
Max # of instructions executed	128	128	1024	65536	65536	Unlimited
Instruction predication
Temp registers	12	12	12	16	32	4096
constant registers	≥ 96	≥ 96	≥ 256	256	≥ 256	16×4096
Address register
Static flow control
Dynamic flow control
Dynamic flow control depth				24	24	64
Vertex texture fetch
of texture samplers					4	128
Geometry instancing support
Bitwise operators
Native integers

See also

• Direct3D
• DirectX
• DirectX Raytracing

External links

• Programming guide for HLSL at Microsoft Docs
• Introduction to the DirectX 9 High Level Shading Language, (ATI) AMD developer central
• Riemer's HLSL Introduction & Tutorial (includes sample code)
• HLSL Introduction
• DirectX Intermediate Language (DXIL) specification

Notes and References

1. Web site: Writing HLSL Shaders in Direct3D 9 . . February 22, 2021.
2. Web site: High-level shader language (HLSL) . . February 22, 2021.
3. Web site: Fusion Industries :: Cg and HLSL FAQ ::. https://web.archive.org/web/20120824051248/http://www.fusionindustries.com/default.asp?page=cg-hlsl-faq. dead. August 24, 2012. August 24, 2012.
4. Web site: Shader Model 5.1 Objects . . February 22, 2021.
5. Web site: HLSL Shader Model 6.0 . . February 22, 2021.
6. Web site: Pixel Shader Differences . . February 22, 2021.
7. Web site: Introduction to the DirectX 9 High-Level Shader Language . Peeper . Craig . Mitchell . Jason L. . July 2003 . . February 22, 2021.
8. Web site: NVIDIA Introduces GeForce FX (NV30) . Shimpi . Anand Lal . Anand Lal Shimpi . . February 22, 2021.
9. Web site: ATI Radeon X800 Pro and XT Platinum Edition: R420 Arrives . Derek . Wilson . . February 22, 2021.
10. Shader Model 3.0, Ashu Rege, NVIDIA Developer Technology Group, 2004.
11. The Direct3D 10 System, David Blythe, Microsoft Corporation, 2006.
12. Web site: Registers - ps_4_1 . . February 22, 2021.
13. Web site: Registers - ps_5_0 . . February 22, 2021.
14. Web site: Vertex Shader Differences . . February 22, 2021.