GAM532DPS932 – Week 3Fragment Shaders

The Shader PipelineVertex

Processing

Primitive Assembly /

Processing

Rasterization

Fragment

Process

Pixel Output

Vertex Data Pixel Color

Clip Space to Fragment Transformation

Clip Space Vertices(Flattened into 2D screen space)

Connect Associated Vertices (Winding order

preserved)

Construct Geometry

Clipping and Backface Culling (Removes

pieces that will not be

seen)

Rasterize (Split the geometry into

fragments, interpolating vertex values)

Fragment Processing in Parallel

#version 430

layout(triangles) in;layout(triangle_strip) out;layout(max_vertices=3) out;

struct BasicGSInput { vec4 position; vec3 normal; vec2 uv; vec4 fragPos; vec3 toLight; };

struct BasicGSOutput { vec4 position; vec3 normal; vec2 uv; vec4 fragPos; vec3 toLight; };

layout (location = 0) in BasicGSInput gin[];layout (location = 0) out BasicGSOutput gout;

void main() { int i; for(i=0; i<gl_in.length(); i++) { gl_Position = gin[i].position; gout.position = gin[i].position; gout.normal = gin[i].normal; gout.uv = gin[i].uv; gout.fragPos = gin[i].fragPos; gout.toLight = gin[i].toLight; EmitVertex(); } EndPrimitive(); }

Uniform Buffers

Linear Interpolation

[ 0, 25, 10]

35

[ 0.707, 0.707, 0 ]

-5

[ -0.707, 0.707, 0 ]

[ 10, 25, 50]

31 23 15 7 -1

1, 25, 14 3, 25, 22 5, 25, 30 7, 25, 38 9, 25, 46

0.566, 0.707, 0 0.283, 0.707, 0 0, 0.707, 0 -0.283, 0.707, 0

-0.566, 0.707, 0

FV = v1 + (v2 – v1) * (FI + 0.5)/FN

VF = v1 + (v2 – v1) * A

Linear Interpolation Issues

31 23 15 7 -1

1, 25, 14 3, 25, 22 5, 25, 30 7, 25, 38 9, 25, 46

0.566, 0.707, 0 0.283, 0.707, 0 0, 0.707, 0 -0.283, 0.707, 0

-0.566, 0.707, 0

35-5237 15 31-1

NOT A Unit Length Vector IS A Unit Length Vector

Interpolated UVs & Texture Sampling

[ 0, 0 ]

[ 1, 0 ]

[ 0, 1 ]

[ 1, 1 ]

[ 0, 10, 0 ]

[ 7, -7, 0 ][ -7, -7, 0 ]

[ 0.5, 0 ]

[ 0, 1 ]

[ 1, 1 ]

[ 0, 1.5, 0 ][ 0.5, 0.5 ]

[ -3 , -2, 0 ][ 0.28, 0.29 ]

Texel

Texture Filtering

Point Sampling(Sample Once)

UV = [0.2,0]

[0, 0, 0]

Linear Sampling(Sample Two Closest, Average)

UV = [0.2,0]

[26,26,26]

[ 0, 0, 0 ] * 1.0

0.2-(1/3)/(1/3)=0.1

[ 0, 0, 0 ] * 0.9 +

[255,255,255] * 0.1

Bilinear Sampling

(Sample Four Closest, Average)

UV = [0.2,0]

[26,26,26]

~Equation above, but in 4 directions

Fragment Shader Inputs & Outputs

Interpolated Fragment Values Uniform Buffers

- Clip Space Position

- UV Coordinates

- World/View Space Surface Normal

- Light Information

- Diffuse Textures

- Diffuse Sampler

Fragment Shader Output

- Pixel Color

Writing Fragment Shaders I/O#version 430struct Light { vec4 diffuse; vec4 specular; vec4 attenuation;};

layout (std140, binding = 9) uniform singleLight { Light light;};

layout(binding = 1) uniform sampler2D diffuse;

struct FragInput { vec4 position; vec3 normal; … };

layout (location = 0) in FragInput fin;layout (location = 0) out vec4 color;void main() {…}

struct Light { float4 diffuse; float4 specular; float4 attenuation;};

cbuffer singleLight : register(b1) { Light light;}

Texture2D diffuse : register(t1);SamplerState diffSamp : register(s1);

struct FragInput { float4 position : SV_POSITION; float3 normal : NORMAL; float2 uv : TEXCOORD0; float4 fragPos : TEXCOORD1; float3 toLight : TEXCOORD2;};

float4 FragmentShaderName(FragInput fin) : SV_Target {…}

Writing Fragment Shader Program

…void FragmentShaderName() { vec4 dTexel = sample2D(diffuse, fin.uv).rgba; color = dTexel;}

…float4 FragmentShaderName(FragInput fin) : SV_Target { float4 dTexel = diffuse.Sample(diffSamp, fin.uv); return dTexel; }

Working with Multiple Textures & Normals

Dot Product with Directions

Dot([0,1,0],[0,1,0]) = 1.0

Dot([0,1,0],[0.707,0.707,0]) = 0.707

Dot([0,1,0],[1,0,0]) = 0.0

Dot([0,1,0],[0.707,-0.707,0]) = -0.707

Dot([0,1,0],[0,-1,0]) = -1.0

Texture1

Texture2

Texture3

Texture4

Sampler1

Sampler2

Adding to Fragment Shader

…layout(binding = 1) uniform sampler2D diffuse;layout(binding = 2) uniform sampler2D diff2;

..

void FragmentShaderName() { vec4 dTexel = sample2D(diffuse, fin.uv).rgba; vec4 eTexel = sample2D(diff2, fin.uv).rgba;

color = float4(0,0,0,1); vec3 nNormal = normalize(vin.normal);

color += max(0, dot(nNormal, vec3(0,1,0)) * dTexel; color += max(0, dot(nNormal, vec3(0,-1,0)) * eTexel;}

…

Texture2D diffuse : register(t1);SamplerState diffSamp : register(s1);Texture2D diff2 : register(t2);SamplerState diffSamp2 : register(s2);

…

float4 FragmentShaderName(FragInput fin) : SV_Target { float4 dTexel = diffuse.Sample(diffSamp, fin.uv); float4 eTexel = diff2.Sample(diffSamp2, fin.uv);

float4 color = float4(0,0,0,1); float3 nNormal = normalize(vin.normal);

color += max(0, dot(nNormal, float3(0,1,0)) * dTexel; color += max(0, dot(nNormal, float3(0,-1,0)) * eTexel;

return color; }

HLSL Semantics

Fragment Shader Input Fragment Shader Output

NORMALn X

COLORn X X

TEXCOORDn X

SV_IsFrontFace X

SV_Position X

SV_Target X

SV_Depth X

DEPTHn X

Effects of the Fragment Shader

Cell Shading Normal Mapping Sub-Surface Scattering

To Do• Read over Lab 2

• Read Week 3 Notes

• Create Team Wiki Page

• Split assignment work between group members