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Hardware Perlin Noise Demonstration
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HARDWARE PERLIN NOISE DEMONSTRATION
by Paul R. Dunn
Perlin noise can be used to make some very impressive looking cloud effects,
but at a substantial cost of processing power. Here is some code that I wrote after
experimenting with Perlin noise. I realized that by using the texture blending
characteristics of todays 3D graphics hardware, you could generate similar effects
on the graphics card and move the burden away from the CPU. And what a heavy burden that is!
This function utilizes a pre-made noise texture and renders it in several passes to
a render surface. The render surface ends up with a texture that resembles perlin
noise and it can be animated like Perlin noise (or rendered into a 3rd dimension like
Perlin noise). The algorithm it turns out, is very simple and uses virtually no CPU.
That's because all of the work is being done on the graphics card. Many graphics engines
could benefit from creating foggy or fiery textures this way rather than on the CPU.
A sample of code follows that was written in C++ with the DirectX9 SDK. The entire application
that this function was extracted from can be downloaded in binary (executable) format here
<HWPerlin.exe> (72KB). It will run on windows
systems with DirectX9 and a 3D card installed. Run the app and press the 'N' key to toggle through
the 3 render styles or 'type's. It generates a texture 512x512 pixels and animates it.
Compare that app to this one
<ClassicPerlin.exe> (56KB)
which generates a texture 256x256 pixels (stretched to 512x512) and is not as smoothly animated.
It is more taxing on the CPU.
Compared with algorithms that generate Perlin noise on the CPU, this algorithm can generate higher
resolution textures and animate them faster just because a CPU isn't designed to handle the kind of
high volume parallel processing that a pixel processor offers.
These images taken from the app at 512x512 were reduced to 256x256 for web publication:
 Base Noise: this noise pattern was generated once in the app.
 Perlin Noise: this pattern was generated by multi texturing the base noise.
 Perlin Noise: each layer was offset differently to produce this pattern.
The primary texture blending function:
/**************************************
pOutputTex is an IDirect3DTexture9* that will be filled with the Perlin noise.
It can later be mapped onto a mesh.
pNoiseTex is a texture filled with a standard noise algorithm. In this program,
I generated one pNoiseTex at the beginning of
the application and used it throughout.
GRIDSIZE is the width and height of the output texture pOutputTex
**************************************/
void NoiseClass::Advance(int type)
{
HRESULT hr;
IDirect3DDevice9* pD3DDev = pRasDev->GetDevice();
DWORD FVF_pV = D3DFVF_XYZRHW | D3DFVF_TEX1;
struct _pV
{
FLOAT x,y,z,rhw;
FLOAT tu,tv;
};
float flim = GRIDSIZE;
_pV pV[] = {
{ 0.f, 0.f, 0.f,1.f, 0.f,0.f },
{ 0.f,flim, 0.f,1.f, 0.f,1.f },
{ flim, 0.f, 0.f,1.f, 1.f,0.f },
{ flim,flim, 0.f,1.f, 1.f,1.f },
};
IDirect3DSurface9* pSurface;
hr = pOutputTex->GetSurfaceLevel(0,&pSurface);
printerr("GetSurfaceLevel",hr);
hr = pD3DDev->SetRenderTarget(0,pSurface);
printerr("SetRenderTarget",hr);
pD3DDev->SetFVF( FVF_pV );
pD3DDev->Clear(0,NULL,D3DCLEAR_TARGET|D3DCLEAR_ZBUFFER,0x00000000,1.f,0);
pD3DDev->BeginScene();
// pNoiseTex is just a basic random noise texture
pD3DDev->SetTexture(0,pNoiseTex);
switch (type)
{
default:
case 0:
// standard
pD3DDev->SetTextureStageState( 0, D3DTSS_COLOROP, D3DTOP_SELECTARG1 );
pD3DDev->SetTextureStageState( 0, D3DTSS_COLORARG1, D3DTA_TEXTURE );
break;
case 1:
// deeper contrast
pD3DDev->SetTextureStageState( 0, D3DTSS_COLOROP, D3DTOP_ADDSIGNED );
pD3DDev->SetTextureStageState( 0, D3DTSS_COLORARG1, D3DTA_TEXTURE );
pD3DDev->SetTextureStageState( 0, D3DTSS_COLORARG2, D3DTA_TEXTURE );
break;
case 2:
// darker or less dense
pD3DDev->SetTextureStageState( 0, D3DTSS_COLOROP, D3DTOP_SUBTRACT );
pD3DDev->SetTextureStageState( 0, D3DTSS_COLORARG1, D3DTA_TEXTURE );
pD3DDev->SetTextureStageState( 0, D3DTSS_COLORARG2, D3DTA_TEXTURE | D3DTA_COMPLEMENT );
break;
}
// use alpha channel to cut ampitude in half while frequency doubles
pD3DDev->SetTextureStageState( 0, D3DTSS_ALPHAOP, D3DTOP_SELECTARG1 );
pD3DDev->SetTextureStageState( 0, D3DTSS_ALPHAARG1, D3DTA_TFACTOR );
// no more texture stages, 1 is enough!
pD3DDev->SetTextureStageState( 1, D3DTSS_COLOROP, D3DTOP_DISABLE );
pD3DDev->SetTextureStageState( 1, D3DTSS_ALPHAOP, D3DTOP_DISABLE );
// standard alpha blending, nothing fancy
pD3DDev->SetRenderState( D3DRS_ALPHABLENDENABLE, TRUE );
pD3DDev->SetRenderState( D3DRS_BLENDOP, D3DBLENDOP_ADD );
pD3DDev->SetRenderState( D3DRS_SRCBLEND, D3DBLEND_SRCALPHA );
pD3DDev->SetRenderState( D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA );
// make the texture map properly
pD3DDev->SetRenderState( D3DRS_CULLMODE, D3DCULL_NONE);
pD3DDev->SetSamplerState( 0, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR );
pD3DDev->SetSamplerState( 0, D3DSAMP_ADDRESSU, D3DTADDRESS_WRAP );
pD3DDev->SetSamplerState( 0, D3DSAMP_ADDRESSV, D3DTADDRESS_WRAP );
static float time = 50.f; // start with a non-zero value
while (time>1024.f) time-=1024.f; // keep time normalized
// the main blending loop: makes pretty perlin noise out of messy random noise
int count = 0;
float scf = 1.f/GRIDSIZE; // scale factor (or frequency of noise)
float shft;
int txf = 0xff; // texture factor (or amplitude of noise)
while (scf0)
{
count++;
shft = time*powf(scf,1.5f) * (GRIDSIZE/1024.f);
pD3DDev->SetRenderState( D3DRS_TEXTUREFACTOR, (txf |
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