graphics graphics lab @ korea university cgvr.korea.ac.kr 1 using vertex shader in directx 8.1 강...

Graphics

cgvr.korea.ac.kr 1 Graphics Lab @ Korea University

Using Vertex Shader in DirectX 8.1

강 신 진

2002. 02. 05

cgvr.korea.ac.kr 2

CGVR

Graphics Lab @ Korea University

Overview

What is Vertex Programming? Vertex Programming Assembly Language Sample Programs

Instruction Set

Graphics


What is Vertex Programming?

Part 1

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Traditional Rendering Pipeline

Traditional Graphics Pipeline

frame-bufferanti-aliasingframe-bufferanti-aliasing

textureblendingtexture

blending

setuprasterizer

setuprasterizer

transform &lighting

transform &lighting

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Vertex Shader Rendering Pipeline

SetVertexShader()

frame-bufferanti-aliasingframe-bufferanti-aliasing

textureblendingtexture

blending

setuprasterizer

setuprasterizer

transform &lighting

transform &lighting

VertexProgramVertex

Program

Switch from standard T&L modeto

Vertex Program mode

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What is Possible?

Complete control of transform and lighting HW Complex vertex operations accelerated in HW Custom vertex lighting Custom skinning and blending Custom texture coordinate generation Custom texture matrix operations Custom vertex computations of your choice Offloading vertex computations frees up CPU

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What is Possible?

Custom transform, lighting, and skinning

Directional Light

Bump Point LightingKeyframe Interpolation

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Vertex Attributes

Vertex Program

Vertex Output

Program Parameters

Temporary Registers Read/Write-able

16x4 registers

128 instructions

96x4 registers

12x4 registers

Read-only

Vertex ProgrammingConceptual Overview

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Vertex ProgrammingConceptual Overview

Vertex Attribute Registers

Vertex Program

Vertex Result Registers

Program Parameter Registers

Temporary Registers

v[0] v[1] … v[15]

c[0] c[1] … c[95]

R0 R1 … R10 R11

oPos, oD0

r

r

r/w

w

Address Register

A0.x

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Sample Code

Position & Constant Color

reg c0 = (0,0.5,1.0,2.0)

reg c4-7 = WorldViewProj matrix

reg c8 = constant color

reg v0 = position ( 4x1 vector )

reg v5 = diffuse color

const char SimpleVertexShader0[] =“

vs.1.0 //Shader version 1.0

m4x4 oPos , v0, c4 //emit projected position

mov oD0, c8 //Diffuse color = c8”

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Vertex Program Assembly language interface to T&L unit GPU instruction set to perform all vertex math Reads an untransformed, unlit vertex Creates a transformed vertex Optionally creates

Lights a vertex Creates texture coordinates Creates fog coordinates Creates point sizes

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Vertex Program Does not create or delete vertices

1 vertex in and 1 vertex out

No topological information provided No edge, face, nor neighboring vertex info

Dynamically loadable

Graphics


Vertex ProgrammingAssembly Language

Part 2

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Instruction Format:

Opcode dst, [-]s0 [,[-]s1 [,[-]s2]]; #comment

Instruction name

Destination Register

Source0 Register

Source1 Register

Source2 Register

Assembly Language Format

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Instruction Format:

Opcode dst, [-]s0 [,[-]s1 [,[-]s2]]; #comment

Instruction name

Destination Register

Source0 Register

Source1 Register

Source2 Register

Example:

MOV r1, r2

R1xyzw

R2xyzw

Assembly Language Format

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Simple Example:

MOV R1, R2;

R1

x

y

z

w

7.0

3.03.0

6.0

2.0

R2

x

y

z

w

7.0

3.0

6.0

2.0

R1

x

y

z

w

0.0

0.0

0.0

0.0

R2

x

y

z

w

7.0

3.0

6.0

2.0

before after

Assembly Example

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Source registers can be negated:

MOV R1, -R2;

before after

R1

x

y

z

w

0.0

0.0

0.0

0.0

R2

x

y

z

w

7.0

3.0

6.0

2.0

R1

x

y

z

w

-7.0

-3.0

-6.0

-2.0

R2

x

y

z

w

7.0

3.0

6.0

2.0

Assembly Example

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Destination register can mask which components are written to…

R1 write all components

R1.x write only x component

R1.xw write only x, w components

Masking

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Destination register masking:

MOV R1.xw, -R2;

before after

R1

x

y

z

w

0.0

0.0

0.0

0.0

R2

x

y

z

w

7.0

3.0

6.0

2.0

R1

x

y

z

w

-7.0

0.0

0.0

-2.0

R2

x

y

z

w

7.0

3.0

6.0

2.0

Masking

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There are 17 instructions in total

• ARL• MOV• MUL• ADD• MAD• RCP

• RSQ• DP3• DP4• DST• MIN• MAX

• SLT• SGE• EXP• LOG• LIT

All Instructions

Graphics


Sample Program

Part 3

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Vertex Shader Frame Work in DX 8.1

Step 1: Declare the vertex data Step 2: Design the shader functionality Step 3: Check for vertex shader support Step 4: Declare the shader registers Step 5: Create the shader Step 6: Render the output pixels

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Step 1

Declare the vertex datastruct CUSTOMVERTEX { FLOAT x, y, z; DWORD diffuseColor; };

#define D3DFVF_CUSTOMVERTEX

(D3DFVF_XYZ|D3DFVF_DIFFUSE)

CUSTOMVERTEX g_Vertices[]= {

{ -1.0f, -1.0f, 0.0f, 0xffff0000 },

{ +1.0f, -1.0f, 0.0f, 0xff00ff00 },

{ +1.0f, +1.0f, 0.0f, 0xff0000ff },

{ -1.0f, +1.0f, 0.0f, 0xffffff00 }, };

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Basic Instruction (Step 2)

DP3: Three-Component Dot Product

Function:

Computes the three-component (x,y,z) dot product of two source vectors and replicates the result across the destination register.

Syntax:

DP3 dest, src0, src1;

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Basic Instruction (Step 2)

before after

DP3 Example:

DP3 R1, R6, R6;

x

y

z

w

R6

3.0

2.0

1.0

1.0

R1

0.0

0.0

0.0

0.0

x

y

z

w

R6

3.0

2.0

1.0

1.0

R1

14.0

14.0

14.0

14.0

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Sample Code – 1 (Step 2)

Position & Diffuse Colorreg c0 = (0,0.5,1.0,2.0)





const char SimpleVertexShader1[] =“vs.1.0 //Shader version 1.0dp4 oPos.x , v0, c4 //emit projected x positiondp4 oPos.y , v0, c5 //emit projected y positiondp4 oPos.z , v0, c6 //emit projected z positiondp4 oPos.w , v0, c7 //emit projected w positionmov oD0, v5 //Diffuse color = vertex color ”

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Position & Texturereg c0 = (0,0.5,1.0,2.0)





reg v7 = texcoords ( 2x1 vector )

const char SimpleVertexShader2[] =“vs.1.0 //Shader version 1.0dp4 oPos.x , v0, c4 //emit projected x positiondp4 oPos.y , v0, c5 //emit projected y positiondp4 oPos.z , v0, c6 //emit projected z positiondp4 oPos.w , v0, c7 //emit projected w positionmov oT0.xy , v7 //copy texcoords”

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Position & Lightingreg c0 = (0,0.5,1.0,2.0)





reg v7 = texcoords ( 2x1 vector )

const char SimpleVertexShader3[] =vs.1.0 //Shader version 1.0dp4 oPos.x, v0, c4 //emit projected x positiondp4 oPos.y, v0, c5 //emit projected y positiondp4 oPos.z, v0, c6 //emit projected z positiondp4 oPos.w, v0, c7 //emit projected w positiondp3 r0.x, v3, c12 //N dot L in world space mul oD0, r0.x , v5 //Calculate color intensity mov oT0.xy , v7 //copy texcoords

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Step 3

Check for vertex shader supportD3DCAPS8 caps; m_pd3dDevice->GetDeviceCaps(&caps);

if( D3DSHADER_VERSION_MAJOR( caps.VertexShaderVersion ) < 1 ) return E_FAIL;

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Step 4

Declare the shader registersDWORD dwDecl[] = { D3DVSD_STREAM(0), D3DVSD_REG(D3DVSDE_POSITION, D3DVSDT_FLOAT3), D3DVSD_REG( D3DVSDE_DIFFUSE, D3DVSDT_D3DCOLOR ),

D3DVSD_END() };

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Step 5

Create the shaderTCHAR strPath[512]; LPD3DXBUFFER pCode; DXUtil_FindMediaFile( strPath, _T("VertexShader.vsh") );

D3DXAssembleShaderFromFile( strPath, 0, NULL, &pCode, NULL );

m_pd3dDevice->CreateVertexShader( dwDecl, (DWORD*)pCode->GetBufferPointer(), &m_hVertexShader, 0 )))

pCode->Release();

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Step 6

Render the output pixelsm_pd3dDevice->SetVertexShaderConstant( 0, &mat, 4 ); float color[4] = {0,1,0,0}; m_pd3dDevice->SetVertexShaderConstant( 4, &color, 1 ); m_pd3dDevice->SetStreamSource( 0, m_pQuadVB,

sizeof(CUSTOMVERTEX) ); m_pd3dDevice->SetVertexShader( m_hVertexShader );

m_pd3dDevice->DrawPrimitive( D3DPT_TRIANGLEFAN, 0, 2 );

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Demo Program

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Performance

For Optimal performance

• Be clever

• Exploit vector parallelism

• (Ex. 4 scalar adds with a vector add)

• Swizzle and negate away

• (no performance penalty for doing so)

• Use LIT and DST effectively

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Summary – Vertex Programs

Increased programmability Customizable engine for transform, lighting,

texture coordinate generation, and more. Facilitates setup for per-fragment shading. Allows animation/deformation through key-frame

interpolation and skinning.

Accelerated in Future Generation GPUs Offloads CPU tasks to GPU yielding higher

performance.

Graphics


The Instruction Set

Appendix

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There are 17 instructions in total

• ARL• MOV• MUL• ADD• MAD• RCP

• RSQ• DP3• DP4• DST• MIN• MAX

• SLT• SGE• EXP• LOG• LIT

All Instructions

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RCP

RCP: Reciprocal

Function:

Inverts the value of the source and replicates the result across the destination register.

Syntax:

RCP dest, src0.C;

where ‘C’ is x, y, z, or w

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RCP

before after

RCP Example:

RCP R1, R2.w;

x

y

z

w

R2

7.0

3.0

6.0

2.0

R1

0.0

0.0

0.0

0.0

x

y

z

w

R2

7.0

3.0

6.0

2.0

R1

0.5

0.5

0.5

0.5

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RSQ

RSQ: Reciprocal Square Root

Function:

Computes the inverse square root of the absolute value of the source scalar and replicates the result across the destination register.

Syntax:

RSQ dest, src0.C;

where ‘C’ is x, y, z, or w

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RSQ

before after

RSQ Example:

RSQ R1.x, R5.x;

x

y

z

w

R5

-4.0

3.0

7.0

9.0

R1

0.0

0.0

0.0

0.0

x

y

z

w

R5

-4.0

3.0

7.0

9.0

R1

0.5

0.0

0.0

0.0

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SLT

SLT: Set On Less Than

Function:

Performs a component-wise assignment of either 1.0 or 0.0. 1.0 is assigned if the

value of the first source is less than the value of the second. Otherwise, 0.0 is assigned.

Syntax:

SLT dest, src0, src1;

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SLT

before after

SLT Example:

SLT R1, R2, R3;

x

y

z

w

R3

2.0

2.1

5.0

7.0

R2

7.0

3.0

6.0

2.0

R1

0.0

0.0

0.0

0.0

x

y

z

w

R3

2.0

2.1

5.0

7.0

R2

7.0

3.0

6.0

2.0

R1

0.0

0.0

0.0

1.0

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LIT

LIT: Light Coefficients

Function:

Computes ambient, diffuse, and specular lighting coefficients from a diffuse dot product, a specular dot product, and a specular power.

Assumes:

src0.x = diffuse dot product (N • L)src0.y = specular dot product (N • H)

src0.w = power (m)

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LIT


Syntax:

LIT dest, src0

Result:

dest.x = 1.0 (ambient coeff.)

dest.y = CLAMP(src0.x, 0, 1) = CLAMP(N • L, 0, 1)

(diffuse coeff.)

dest.z = (see next slide…) (specular

coeff.) dest.w = 1.0

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LIT


Result: (Recall: src0.x N • L)

if ( src0.x > 0.0 ) dest.z = (MAX(src0.y,0))

(ECLAMP(src0.w,-128,128)) = (MAX(N • H,0))m

where m in (-128,128)

otherwise, dest.z = 0.0

(dest.z is specular coeff. as defined by OpenGL)

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LIT

before after

LIT Example:

LIT R1, R7;

x

y

z

w

R7

0.3

0.8

0.0

2.0

R1

0.0

0.0

0.0

0.0

R7

0.3

0.8

0.0

2.0

x

y

z

w

R1

1.0

0.3

0.64

1.0

(ambient)

(diffuse)

(specular)

(Good to 8+ bits)

graphics graphics lab @ korea university cgvr.korea.ac.kr 1 using vertex shader in directx 8.1 강...

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