Cg is a high-level shading language that is used to program the vertex and fragment shaders in Unity. Cg shaders allow for complex pixel processing and GPU calculations. In Unity, shaders are written using the Cg language and compiled for the target graphics API. Shaders have inputs like vertex attributes and uniforms, and outputs like varying values passed between stages. Common shader types include surface, vertex, and fragment shaders. Advanced techniques like multi-pass rendering are also possible in Unity using Cg shaders.

1. Cg Shaders with Unity
By Michael Ivanov
3D Graphics Geek

2. What are Shaders.

3. Geometry Deformation.
Pixels processing.
Math intensive calculations.
GPGPU.

4. • D3D / OpenGL Render Pipeline Stages
Hull Tessellator Stage Domain
Tessellation Geometry Shader
Vertex Primitive
Vertex Shader Rasterization
Assembly Assembly
Raster
Screen Pixels Fragment Shader
Operations

5. Vertex Shader

6. • Runs per input vertex.
• Transform 3D into 2D (screen space) position.
• Can perform vertex position , color , UV (texture coordinates)
manipulation.
• Cannot create new vertices.
• Cannot “see” other vertices.

7. Fragment (Pixel) Shader

8. • Runs per fragment.
• Computes fragment’s color.
• With fragment shader you can create: bump
mapping, shadows , lights , post processing effects and other
cool shit.
• See http://glsl.heroku.com/

9. What is Cg language?

10. Shaders before Cg/HLSL/GLSL:
TEX H0, f[TEX0], TEX4, 2D;
TEX H1, f[TEX2], TEX5, CUBE;
DP3X H1.xyz, H1, LUMINANCE;
MULX H0.w, H0.w, LUMINANCE.w;
MULX H1.w, H1.x, H1.x;
MOVH H2, f[TEX3].wxyz;
MULX H1.w, H1.x, H1.w;
DP3X H0.xyz, H2.xzyw, H0;
MULX H0.xyz, H0, H1.w;
TEX H1, f[TEX0], TEX1, 2D;
TEX H3, f[TEX0], TEX3, 2D;
MULX H0.xyz, H0, H3;
….
………
…………..

11. • “C for graphics”
• High Level language.
Cg != C
• No classes ,pointers ,malloc ,IO etc.
• Cg has loops , conditionals , functions/overloads.
• Member variables ,local (temporary) variables constants.
• Data types: numeric primitives ,vectors , matrices
,arrays, structs and interfaces.
• Built-in trig and other math methods.
• Static & Dynamic compilation.

12. • Cg and Graphics APIs interop scheme:

13. How it works in Unity

14. 3 Ways of writing shaders in Unity:
1. Surface shaders.
2. Vertex and fragment shaders.
3. Fixed function shaders.

15. Simple Custom shader:

16. • CG Program inputs / outputs(Show code example):
Inputs
1. Varying inputs(Attributes) –streamed data VARYING per
processed element.(Vertex arrays ,UV arrays,normal arrays)
2. Uniform inputs(Uniforms)-separate from the main stream
values which don’t change each stream element.(Matrices
, vectors)
Outputs
1. Varying outputs – interpolated values sent from Vertex to
Fragment shader.
2. Binding Semantics for fragment program output: COLOR
semantic is must to have!

17. Per Frame varying data from CPU:
Uniform Uniform
variables variables
Variables
Variables
Variables
Variables
Output
Output
Input
Vertex
Input
Attributes
Vertex Shader Fragment Shader
Frame Buffer / Texture Attachment

18. Passing vertex attributes and uniforms.
• Programmable setup (via scripts): (demo)
SetFloat(),SetVector(),SetMatrix(),SetColor(),SetBuffer(),SetTexture().
• Shader lab properties:
[UniformName+(*“Uniform property panel name“+, *Data Type+) = [Default value]
• Attributes definitions are hooked to Mesh object directly:

19. Accessing vertex attributes
Vertex attributes structs are defined in UnityCG.cginc include file
• appdata_base: vertex consists of position, normal and one texture coordinate.
• appdata_tan: vertex consists of position, tangent, normal and one texture coordinate.
• appdata_full: vertex consists of position, tangent, normal, two texture coordinates and color.
We can define our own vertex attribute structs but must use the following names for the
members:
• float4 vertex is the vertex position
• float3 normal is the vertex normal
• float4 texcoord is the first UV coordinate
• float4 texcoord1 is the second UV coordinate
• float4 tangent is the tangent vector (used for normal mapping)
• float4 color is per-vertex color

20. Accessing uniforms:
Very simple:
Declare uniforms in the shader header with exactly the same names and data types as they have
in Shader Lab prop block.

21. Some demos.

22. Post-process shaders

23. • DOF ,SSAO, Motion Blur , Gaussian Blur ,Glow ,Blum etc.
• Done via accessing Frame Buffer texture.

24. Some more demos.

25. Advanced stuff: multi-pass shading.

26. • Used for advanced effects.
• Done using “pass” blocks.
//first pass
pass {
… shader program code here:
}
GrabPass{} //pass first pass output into second pass
//second pass//
pass{
… shader program code here:
}

27. Even more demos.

28. Thank you.
il.linkedin.com/pub/michael-ivanov/16/570/a0a/
explomaster@gmail.com
blog.alladvanced.net

29. Resources
• http://aras-p.info/blog/
• http://docs.unity3d.com/Documentation/Manual/Shaders.html
• http://http.developer.nvidia.com/CgTutorial/cg_tutorial_chapter01.html
• https://developer.nvidia.com/shader-library
• http://wiki.unity3d.com/index.php/Shaders