High Level Shader Language

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The High Level Shader Language or High Level Shading Language (HLSL) is a proprietary shading language developed by Microsoft for use with the Microsoft Direct3D API. It 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.[1]

HLSL programs come in three forms, vertex shaders, geometry shaders, and pixel (or fragment) 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 coefficents such as the vertex's tangent, binormal and normal 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 rasterisation. Each of these pixels comes through the pixel shader, whereby the resultant screen colour is calculated.

Optionally, an application using a Direct3D10 interface and Direct3D10 hardware may also specify a geometry shader. This shader takes as its input the three vertices of a triangle and uses this data to generate (or tessellate) additional triangles, which are each then sent to the rasterizer.

Contents

[edit] Shader model comparison

[edit] Pixel shader comparison

Pixel shader version 2.0 2.0a 2.0b 3.0[2] 4.0[3]
Dependent texture limit 8 No Limit 8 No Limit No Limit
Texture instruction limit 32 Unlimited Unlimited Unlimited Unlimited
Position register No No No Yes Yes
Instruction slots 32 + 64 512 512 ≥ 512 ≥ 65536
Executed instructions 32 + 64 512 512 65536 Unlimited
Texture indirections 4 No limit 4 No Limit No Limit
Interpolated registers 2 + 8 2 + 8 2 + 8 10 32
Instruction predication No Yes No Yes No
Index input registers No No No Yes Yes
Temp registers 12 22 32 32 4096
Constant registers 32 32 32 224 16x4096
Arbitrary swizzling No Yes No Yes Yes
Gradient instructions No Yes No Yes Yes
Loop count register No No No Yes Yes
Face register (2-sided lighting) No No No Yes Yes
Dynamic flow control No No No 24 Yes
Bitwise Operators No No No No Yes
Native Integers No No No No Yes
  • PS 2.0 = DirectX 9.0 original Shader Model 2 specification.
  • PS 2.0a = NVIDIA GeForce FX-optimized model.
  • PS 2.0b = ATI Radeon X700, X800, X850 shader model, DirectX 9.0b.
  • PS 3.0 = Shader Model 3.
  • PS 4.0 = Shader Model 4.

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

[edit] Vertex shader comparison

Vertex shader version VS 2.0 VS 2.0a VS 3.0[2] VS 4.0[3]
# of instruction slots 256 256 ≥ 512 4096
Max # of instructions executed 65536 65536 65536 65536
Instruction Predication No Yes Yes Yes
Temp Registers 12 13 32 4096
# constant registers ≥ 256 ≥ 256 ≥ 256 16x4096
Static Flow Control Yes Yes Yes Yes
Dynamic Flow Control No Yes Yes Yes
Dynamic Flow Control Depth No 24 24 Yes
Vertex Texture Fetch No No Yes Yes
# of texture samplers N/A N/A 4 128
Geometry instancing support No No Yes Yes
Bitwise Operators No No No Yes
Native Integers No No No Yes
  • VS 2.0 = DirectX 9.0 original Shader Model 2 specification.
  • VS 2.0a = NVIDIA GeForce FX-optimized model.
  • VS 3.0 = Shader Model 3.
  • VS 4.0 = Shader Model 4.

[edit] External links

[edit] Footnotes

  1. ^ Fusion Industries :: Cg and HLSL FAQ ::
  2. ^ a b Shader Model 3.0, Ashu Rege, NVIDIA Developer Technology Group, 2004.
  3. ^ a b The Direct3D 10 System, David Blythe, Microsoft Corporation, 2006.
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