nvFX: A Scene and Material Effect Framework for OpenGL

Tristan Lorach - NVIDIA

What is an Effect ?

Application

Effect

runtime

Effect file

Shader func’s

Sampler-states

Parameters

Techniques

Passes

Render-states

Texture Samplers

Textures (D3D) GPU

Shaders

Render

states

… • Set params (1 by 1 )

• Validate passes (builds shaders)

• Bind textures/samplers

• Activate a Pass

Introduced in Cg (2002) and HLSLFx

nvFX features

Candidate to replace CgFx

Hosts many Shading Languages (GLSL, GLSLCompute, HLSL, Compute…)

Effect == container of Shader snippets

self sufficient Effects

Lower amount C++ specialized code for the effect

Intermediate resources (Render-Targets) can be defined

Flexible Shader-snippets linkage approach

Nesting of Effects

Example: Scene-Effects influences Material Effects

Add more features

New Pass-states; resources; Constant Buffers; namespace; GL Extensions…

Open-Source

Inside An nvFX Effect

nvFX file

Sampler-states Uniform

Parameters

Techniques

Passes New Pass-states

Texture Bind point

Render

state-groups

Shader Code Modules

GLSL

D3D

Open-CL

GLSL-Compute

DXCompute

Resources

(render targets)

Frame buffers

Constant

Buffers

Resources description

Compute

[shared] Memory

CUDA

Simple nvFX Example

#extension GL_ARB_separate_shader_objects : enable

GLSLShader {

#version 410 compatibility

…

}

uniform vec4 scaleBias : SCBIAS = {1,0,0,0};

Namespace Object {

GLSLShader VS {

layout(location=0) in vec4 Position;

void main() { … }

}

GLSLShader PS < myAnnot=“bar”; > {

layout(location=0) in vec3 v2fWorldNormal;

uniform sampler2D diffSampler;

Main() { … }

}

}

rasterization_state myRStates {

POLYGON_MODE = FILL;

…

}

sampler_state defaultSamplerState

{ TEXTURE_MIN_FILTER = LINEAR_MIPMAP_LINEAR;

TEXTURE_MAG_FILTER = LINEAR;

}

Resource2D diffTex {

samplerState = defaultSamplerState;

defaultFile = "gargoyleMossyDiffuse.dds";

}

Technique BasicTechnique {

Pass p1 < annot1=“Foo”; annot2=3; > {

rasterization_state = myRStates;

samplerResource(diffSampler) = { diffTex, 0 };

VertexProgram = Object::VS;

FragmentProgram = Object::PS;

FragmentProgram<“light”> = LightingImpl;

Uniform(attenuation) = 0.9;

CurrentTarget = backbuffer;

}

Technique mySubTechnique1 Off

Technique mySubTechnique2 On

}

nvFX Effect Integration

Application

nvFX

runtime

nvFX files Shader code

Techs/passes

…

Shader code

Techs/passes

nvFX files

Application

nvFX

runtime

Techs/passes

…

Techs/passes

Application

nvFX

runtime Pre-

compiled

shaders

C++

nvFX

Effects

nvFX files

Shader code Shader code

Techs/passes Techs/passes

…

Shader code Shader code

Pre-

compiled

shaders

Shader code

API Design

Front-End : parser (Bison)

Parses the effect

Does not parse the shader/compute

code that is inside !

Back-End : the library to build the

effect data

Used by the Front-End to create parsed

data

Used by the application to drive the

effects

Works on PC, Unix (OSX/Linux),

Android… even iOS

Front-End

(nvFX parser)

C++ Back-End

(nvFX runtime)

API

Application

Your

Front-End

Parser

OpenGL DX Compute

Your Gfx API layer

Custom Grammar

& Token

DEMOS

1

Example : HDR Rendering With Glow

Render

Skybox in HDR

Render The

Scene in HDR

Down-scale the

texture 2x, 4x

Blur texture

Horizontal

Then Vertical

Scene Effect

1

2

3

4

5

6

Material Effect 1

Metal Pass

Material Effect 2

Plastic pass

Scene Graph

Other ‘Effects’…

RGBA32F

Texture

(HDR)

Compositing:

tone-mapping

And radial Blur

7

RGBA

32F

Texture

Backbuffer

+

2 3

4 5 6 7 7

Example : Compute Post-Processing

Render

Skybox

Render The

Scene

Triggers

Compute

Kernel

Display result

As a fullscreen

Quad

Scene Effect passes

1

2

3

4

Material Effect 1

Metal Pass

Material Effect 2

Plastic pass

Scene Graph

Other ‘Effects’…

RGBA

Texture

Backbuffer

Fire (Navier-Stokes equations) Techniq

ue

Advect Color

Advect Velocity

Vorticity

Confinement

Emit (Gaussian ball)

Fire Up-force

Vel. divergence

Comp. pressure

Proj. Velocity

Proj. Vel. edges passes

Volume bound 1

Volume bound 2

Smoke Ray-cast

Water Ray-cast

Fire Ray-cast

Rasterize result

Simulation passes

Techniques

Volume depth Volume depth

Rasterize

4

1

2

3

Conclusion

Less code in Application

More flexibility

Consistency of Effect code. Helps for maintenance and creativity

Updated use of modern APIs. Good for performance

Open-Source approach

Easier to track bugs

Customize it… make it yours or get inspiration from it

First drop now available on https://github.com/tlorach/nvFX

Feedback Needed to improve it : tlorach@nvidia.com

More details from previous talks (GTC 2013, Siggraph NVIDIA talks)