diewald_fluid glitches/artifacts

any_user

diewald_fluid glitches/artifacts

in Contributed Library Questions • 1 year ago

We're using the diewald_fluid library for a project and are experiencing glitches/artifacts when the fluid is NOT moving (no velocity changes for any cells). There are horizontal and vertical lines appearing at regular intervals and one diagonal line. They appear after density is added with addDensity and diffusion is on (to let it fade out). diffusionIterations is set to 1, because for the project the fluid has to fade out but not to diffuse into other pixels.

It is hard to strip the problem down to a specific code section, so I just would like to ask if somebody experienced similar artifacts? Any hints where to search?

Replies(5)

thomas.di..

Re: diewald_fluid glitches/artifacts

1 year ago

indeed a strange result, could you provide a small code-example that reproduces the poblem?
because when i modify one of the examples from the library, with respect to your description, i works as expected.

also it probably would help to know:
your OS, processing version, GLgraphics-version (in case you got this result, using the GPU-mode)

trytobuy

Re: diewald_fluid glitches/artifacts

1 year ago

OSX (10.6 and 10.7), Processing 1.5 and (I'm not sure, any_user, but I think) 1.0.0 of GLgraphics...

With a max-patch it's possible to control the parameters
MaxPatch

import javax.media.opengl.*;
import processing.opengl.*;
import jsyphon.*;
import processing.opengl.*;
import codeanticode.glgraphics.*;
import diewald_fluid.Fluid2D;
import diewald_fluid.Fluid2D_CPU;
import diewald_fluid.Fluid2D_GPU;
import oscP5.*;
import netP5.*;

OscP5 oscP5;
NetAddress myRemoteLocation;

int fluid_size_x = 400;
int fluid_size_y = 200;

int cell_size    = 3;
int window_size_x = fluid_size_x * cell_size + (cell_size * 2);
int window_size_y = fluid_size_y * cell_size + (cell_size * 2);

Fluid2D fluid;
PImage output_densityMap;

JSyphonServer syphon;
GLTexture tex;

int[] inputs = new int[2];
int[] prevInputs = new int[2];

boolean isresetting;

GLGraphicsOffScreen canvas;

void setup() {

size(window_size_x, window_size_y, GLConstants.GLGRAPHICS);
frameRate(60);

// prepare fluid
fluid = createFluidSolver();

// prepare syphon
syphon = new JSyphonServer();
syphon.test();
syphon.initWithName("FluidTest");

// prepare tex
tex = new GLTexture(this);

// prepare off screen canvas
canvas = new GLGraphicsOffScreen(this,getWidth(),getHeight());

// start OSC
oscP5 = new OscP5(this,12000);
myRemoteLocation = new NetAddress("127.0.0.1",12000);
}

void draw()
{

if (isresetting){
    fluid.reset();
     fluid.setDensityMap(output_densityMap);
    isresetting = false;
}

// update fluid
if ( mousePressed )
    fluidInfluence(fluid,inputs);

setVel (fluid, 10, 10, 2, 1, .2f, .2f);
setDens(fluid, 10, 10, 8, 8, 4, 4, 4);

setVel (fluid, width-10, cell_size*4, 2, 2, -.2f, .2f);
setDens(fluid, width-10, cell_size*4, 8, 8, 4, 4, 4);

// setVel (fluid, width-10, height-10, 2, 2, -.2f, -.2f);
// setDens(fluid, width-10, height-10, 8, 8, 0, 0, 0);

// setVel (fluid, 10, height-10, 2, 2, .2f, -.2f);
// setDens(fluid, 10, height-10, 8, 8, 4, 0, 0);

fluid.smoothDensityMap(!( keyPressed && key == 's'));

fluid.update();

// draw
canvas.beginDraw();
canvas.background(255);
//canvas.scale(1,-1);
canvas.image(fluid.getDensityMap(), 0, 0, width, height);
canvas.endDraw();

GLTexture tex = canvas.getTexture();
background(255);
image(tex, 0, 0);

syphon.publishFrameTexture(tex.getTextureID(), tex.getTextureTarget(), 0, 0, tex.width, tex.height, tex.width, tex.height, false);
}

void oscEvent(OscMessage theOscMessage) {
/* print the address pattern and the typetag of the received OscMessage */
print("### received an osc message.");
print(" addrpattern: "+theOscMessage.addrPattern());
println(" typetag: "+theOscMessage.typetag());
theOscMessage.print();

String address = theOscMessage.addrPattern();
if( theOscMessage.checkTypetag("i"))
{
   int intValue = theOscMessage.get(0).intValue();

if( address.equals("timeStep") ){
    fluid.setParam_Timestep(intValue*0.001);
}
if( address.equals("vorticity") ){
    fluid.setParam_Vorticity(intValue*0.1);
}
if( address.equals("viscosity") ){
    fluid.setParam_Viscosity(intValue*0.00000005);
}
if( address.equals("diffusion") ){
    fluid.setParam_Diffusion(intValue*0.00000001);
}
if( address.equals("reset") ){
    isresetting = true;
}
}
}

Fluid2D createFluidSolver()
{
Fluid2D fluid_tmp = new Fluid2D_GPU(this, fluid_size_x, fluid_size_y); // initialize de solver

fluid_tmp.setParam_Timestep ( 0.10f );
fluid_tmp.setParam_Iterations( 16 );
fluid_tmp.setParam_IterationsDiffuse(1);
fluid_tmp.setParam_Viscosity ( 0.00000001f );
fluid_tmp.setParam_Diffusion ( 0.0000000001f );
fluid_tmp.setParam_Vorticity ( 2.0f );
fluid_tmp.processDensityMap ( true );
fluid_tmp.processDiffusion   ( true );
fluid_tmp.processViscosity   ( true );
fluid_tmp.processVorticity   ( true );
fluid_tmp.processDensityMap ( true );
fluid_tmp.setObjectsColor    (1, 1, 1, 1);
output_densityMap    = createImage(window_size_x, window_size_y, RGB);
fluid_tmp.setDensityMap(output_densityMap);
return fluid_tmp;
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////
// fluidInfluence();
//
public void fluidInfluence( Fluid2D fluid2d, int[] inputs ) {
if (mouseButton == LEFT ) {
     setDens(fluid2d,mouseX,mouseY, 5, 5, 2, 2, 2);
}

if (mouseButton == RIGHT ) {
    float vel_fac = 0.13f;
    setVel(fluid2d, mouseX, mouseY, 2, 2, (mouseX - pmouseX)*vel_fac, (mouseY - pmouseY)*vel_fac);
    //setVel(fluid2d, inputs[0], inputs[1], 2, 2, (inputs[0] - prevInputs[0])*vel_fac, (inputs[1] - prevInputs[1])*vel_fac);
}
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////
// setDens();
//
void setDens(Fluid2D fluid2d, int x, int y, int sizex, int sizey, float r, float g, float b) {
for (int y1 = 0; y1 < sizey; y1++) {
    for (int x1 = 0; x1 < sizex; x1++) {
      int xpos = (int)(x/(float)cell_size) + x1 - sizex/2;
      int ypos = (int)(y/(float)cell_size) + y1 - sizey/2;
      fluid2d.addDensity(0, xpos, ypos, r);
      fluid2d.addDensity(1, xpos, ypos, g);
      fluid2d.addDensity(2, xpos, ypos, b);
    }
}
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////
// setVel();
//
void setVel(Fluid2D fluid2d, int x, int y, int sizex, int sizey, float velx, float vely) {
for (int y1 = 0; y1 < sizey; y1++) {
    for (int x1 = 0; x1 < sizex; x1++) {
      int xpos = (int)((x/(float)cell_size)) + x1 - sizex/2;
      int ypos = (int)((y/(float)cell_size)) + y1 - sizey/2;
      fluid2d.addVelocity(xpos, ypos, velx, vely);
    }
}
}

/////////////////////////////////////////////////////////////////////////////////////////////////////////////
// addObject();
//
public void addObject(Fluid2D fluid2d, int posx, int posy, int sizex, int sizey, int mode) {
int offset = 0;
int xlow = posx;
int xhig = posx + sizex;
int ylow = posy;
int yhig = posy + sizey;

for (int x = xlow-offset ; x < xhig+offset ; x++) {
    for (int y = ylow-offset ; y < yhig+offset ; y++) {
      if ( x < 0 || x >= fluid2d.getSizeXTotal() || y < 0 || y >= fluid2d.getSizeYTotal() )
        continue;
      if ( mode == 0) fluid2d.addObject(x, y);
      if ( mode == 1) fluid2d.removeObject(x, y);
    }
}
}

greez

any_user

Re: diewald_fluid glitches/artifacts

1 year ago

here's a version which doesn't need max to reproduce the effect. just click somewhere inside the window to see it.

import javax.media.opengl.*;
import processing.opengl.*;
import processing.opengl.*;
import codeanticode.glgraphics.*;
import diewald_fluid.Fluid2D;
import diewald_fluid.Fluid2D_CPU;
import diewald_fluid.Fluid2D_GPU;
int fluid_size_x = 400;
int fluid_size_y = 200;
int cell_size = 3;
int window_size_x = fluid_size_x * cell_size + (cell_size * 2);
int window_size_y = fluid_size_y * cell_size + (cell_size * 2);
Fluid2D fluid;
PImage output_densityMap;
void setup() {
size(window_size_x, window_size_y, GLConstants.GLGRAPHICS);
frameRate(60);
// prepare fluid
fluid = createFluidSolver();
}
void draw()
{
// update fluid
if ( mousePressed )
fluidInfluence(fluid);
setVel (fluid, 10, 10, 2, 1, .2f, .2f);
setDens(fluid, 10, 10, 8, 8, 4, 4, 4);
setVel (fluid, width-10, cell_size*4, 2, 2, -.2f, .2f);
setDens(fluid, width-10, cell_size*4, 8, 8, 4, 4, 4);
fluid.smoothDensityMap(!( keyPressed && key == 's'));
fluid.update();
background(255);
image(fluid.getDensityMap(), 0, 0, width, height);
}
Fluid2D createFluidSolver()
{
Fluid2D fluid_tmp = new Fluid2D_GPU(this, fluid_size_x, fluid_size_y); // initialize de solver
fluid_tmp.setParam_Timestep ( 0.10f );
fluid_tmp.setParam_Iterations( 16 );
fluid_tmp.setParam_IterationsDiffuse(1);
fluid_tmp.setParam_Viscosity ( 0.00000001f );
fluid_tmp.setParam_Diffusion ( 0.0000010001f );
fluid_tmp.setParam_Vorticity ( 2.0f );
fluid_tmp.processDensityMap ( true );
fluid_tmp.processDiffusion ( true );
fluid_tmp.processViscosity ( true );
fluid_tmp.processVorticity ( true );
fluid_tmp.processDensityMap ( true );
fluid_tmp.setObjectsColor (1, 1, 1, 1);
output_densityMap = createImage(window_size_x, window_size_y, RGB);
fluid_tmp.setDensityMap(output_densityMap);
return fluid_tmp;
}
/////////////////////////////////////////////////////////////////////////////////////////////////////////////
// fluidInfluence();
//
public void fluidInfluence( Fluid2D fluid2d ) {
if (mouseButton == LEFT ) {
setDens(fluid2d,mouseX,mouseY, 500, 500, 2, 2, 2);
}
if (mouseButton == RIGHT ) {
float vel_fac = 0.13f;
setVel(fluid2d, mouseX, mouseY, 2, 2, (mouseX - pmouseX)*vel_fac, (mouseY - pmouseY)*vel_fac);
}
}
/////////////////////////////////////////////////////////////////////////////////////////////////////////////
// setDens();
//
void setDens(Fluid2D fluid2d, int x, int y, int sizex, int sizey, float r, float g, float b) {
for (int y1 = 0; y1 < sizey; y1++) {
for (int x1 = 0; x1 < sizex; x1++) {
int xpos = (int)(x/(float)cell_size) + x1 - sizex/2;
int ypos = (int)(y/(float)cell_size) + y1 - sizey/2;
fluid2d.addDensity(0, xpos, ypos, r);
fluid2d.addDensity(1, xpos, ypos, g);
fluid2d.addDensity(2, xpos, ypos, b);
}
}
}
/////////////////////////////////////////////////////////////////////////////////////////////////////////////
// setVel();
//
void setVel(Fluid2D fluid2d, int x, int y, int sizex, int sizey, float velx, float vely) {
for (int y1 = 0; y1 < sizey; y1++) {
for (int x1 = 0; x1 < sizex; x1++) {
int xpos = (int)((x/(float)cell_size)) + x1 - sizex/2;
int ypos = (int)((y/(float)cell_size)) + y1 - sizey/2;
fluid2d.addVelocity(xpos, ypos, velx, vely);
}
}
}
/////////////////////////////////////////////////////////////////////////////////////////////////////////////
// addObject();
//
public void addObject(Fluid2D fluid2d, int posx, int posy, int sizex, int sizey, int mode) {
int offset = 0;
int xlow = posx;
int xhig = posx + sizex;
int ylow = posy;
int yhig = posy + sizey;
for (int x = xlow-offset ; x < xhig+offset ; x++) {
for (int y = ylow-offset ; y < yhig+offset ; y++) {
if ( x < 0 || x >= fluid2d.getSizeXTotal() || y < 0 || y >= fluid2d.getSizeYTotal() )
continue;
if ( mode == 0) fluid2d.addObject(x, y);
if ( mode == 1) fluid2d.removeObject(x, y);
}
}
}

thomas.di..

Re: diewald_fluid glitches/artifacts

1 year ago

the second code-example clearly shows that there is some bug inside the library (i guess in one of the shaders).

the bad news is, that i cant figure out what exactly causes this artifacts, so for now, until i get some ideas what could fix this, i suggest to increase the values:

fluid_tmp.setParam_Iterations( 20 );
fluid_tmp.setParam_IterationsDiffuse(20);

20 is the original value, you can try to lower this value until the artifacts become visible. this may slow down your app, but since you using the GPU mode you probably wont notice it.

to sum up, the artifacts will/should dissapear, when you increase the value for the iteration-parameters, or decrease the value for the diffusion parameter ... so you somehow have to find a compromise.

sorry for that, but thanks for pointing out the error.

any_user

Re: diewald_fluid glitches/artifacts

1 year ago

Ok, that seems to hide the problem, thanks. Our problem is now that we're using a diffuse iterations value of 1 to prevent diffusion into other cells but still have the fade-out effect. Let's see if we can achieve the desired behaviour with this iterations value.