diego/fluids
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Added grid render.

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Added particle toggle.
Added boundary shape adjustment.
This commit is contained in:
iegod
2025-12-05 09:22:20 -05:00
parent d37413a400
commit a15c89d769
4 changed files with 225 additions and 93 deletions
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171
fluid/fluid.go
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@@ -4,6 +4,7 @@
package fluid
import (
"fluids/utils"
"math"
)
@@ -30,15 +31,16 @@ type Fluid struct {
pNumX, pNumY int //SPATIAL HASHING: number of particle cells x,y
pNumCells int //SPATIAL HASHING: number of particle cells in total
pInvSpacing float32 //SPATIAL HASHING: one over the particle spacing
particleDensity []float32 //density of particles within each field cell
particleRestDensity float32
ParticleDensity []float32 //density of particles within each field cell
ParticleRestDensity float32
fluidDensity float32
angle float32
dt float32 //delta time step
gravitynormal FieldVector //unit vector for gravity
stepacceleration FieldVector //step acceleration due to gravity
flipPicRatio float32
numSubSteps int //number of simulation substeps
numSubSteps int //number of simulation substeps
Block bool //rectangular or circular field container
}
func NewFluid(dimensions FieldVector, spacing float32) *Fluid {
@@ -46,9 +48,10 @@ func NewFluid(dimensions FieldVector, spacing float32) *Fluid {
Field: NewVelocityField(dimensions, spacing),
dt: FluidDefaultTimeStep,
fluidDensity: FluidDefaultDensity,
particleRestDensity: FluidDefaultRestDensity,
ParticleRestDensity: FluidDefaultRestDensity,
flipPicRatio: FluidDefaultFlipPicRatio,
numSubSteps: FluidDefaultSubSteps,
Block: true,
}
f.Initialize()
@@ -59,7 +62,7 @@ func (f *Fluid) Initialize() {
f.InitializeParticles()
f.SetAngle(FluidDefaultAngle)
f.particleDensity = make([]float32, f.Field.Nx*f.Field.Ny)
f.ParticleDensity = make([]float32, f.Field.Nx*f.Field.Ny)
}
func (f *Fluid) InitializeParticles() {
@@ -158,32 +161,6 @@ func (f *Fluid) IntegrateParticles() {
}
}
// returns adjusted value between start and end, whichever is closer
// unless value is between, in which case it returns value
func clamp(value, start, end int) int {
if value < start {
return start
}
if value < end {
return value
}
return end
}
func clamp32(value, start, end float32) float32 {
if value < start {
return start
}
if value < end {
return value
}
return end
}
func (f *Fluid) PerformParticleSpatialHash() {
clear(f.numCellParticles)
@@ -191,8 +168,8 @@ func (f *Fluid) PerformParticleSpatialHash() {
//find spatcial hash cell for this particle's position, increment count there
for i := range f.Particles {
p := &f.Particles[i]
xi := clamp(int(p.Position.X*f.pInvSpacing), 0, f.pNumX-1)
yi := clamp(int(p.Position.Y*f.pInvSpacing), 0, f.pNumY-1)
xi := utils.Clamp(int(p.Position.X*f.pInvSpacing), 0, f.pNumX-1)
yi := utils.Clamp(int(p.Position.Y*f.pInvSpacing), 0, f.pNumY-1)
cellnumber := xi*f.pNumY + yi
f.numCellParticles[cellnumber]++
}
@@ -209,8 +186,8 @@ func (f *Fluid) PerformParticleSpatialHash() {
//firstCellParticle bucket as we go
for i := range f.Particles {
p := &f.Particles[i]
xi := clamp(int(p.Position.X*f.pInvSpacing), 0, f.pNumX-1)
yi := clamp(int(p.Position.Y*f.pInvSpacing), 0, f.pNumY-1)
xi := utils.Clamp(int(p.Position.X*f.pInvSpacing), 0, f.pNumX-1)
yi := utils.Clamp(int(p.Position.Y*f.pInvSpacing), 0, f.pNumY-1)
cellnumber := xi*f.pNumY + yi
f.firstCellParticle[cellnumber]--
f.cellParticleIds[f.firstCellParticle[cellnumber]] = i
@@ -291,32 +268,78 @@ func (f *Fluid) HandleParticleCollisions() {
minDist2 := minDist * minDist
*/
minX := f.particleRadius
maxX := float32(f.Field.Nx-1)*f.Field.H - f.particleRadius
minY := f.particleRadius
maxY := float32(f.Field.Ny-1)*f.Field.H - f.particleRadius
if f.Block {
minX := f.Field.H + f.particleRadius
maxX := float32(f.Field.Nx-1)*f.Field.H - f.particleRadius
minY := f.Field.H + f.particleRadius
maxY := float32(f.Field.Ny-1)*f.Field.H - f.particleRadius
for i := range f.Particles {
p := &f.Particles[i]
for i := range f.Particles {
p := &f.Particles[i]
if p.Position.X < minX {
p.Position.X = minX
if p.Position.X < minX {
p.Position.X = minX
p.Velocity.X = 0
}
if p.Position.X > maxX {
p.Position.X = maxX
p.Velocity.X = 0
}
if p.Position.Y < minY {
p.Position.Y = minY
p.Velocity.Y = 0
}
if p.Position.Y > maxY {
p.Position.Y = maxY
p.Velocity.Y = 0
}
}
} else {
//find fluid cell in which the particle resides
//compute distance of this cell from 'center' cell of our circle
//if distance exceeds radius, clamp particle velocity and position
//to edge cell
//find origin of circle, conveniently these dimensions are also our radius
originX := float32(f.Field.Nx) * f.Field.H / 2
originY := float32(f.Field.Ny) * f.Field.H / 2
radius := originX - f.Field.H - f.particleRadius
//cxi := utils.Clamp(int(math.Floor(float64(originX*f.Field.InvH))), 0, f.Field.Nx-1)
//cyi := utils.Clamp(int(math.Floor(float64(originY*f.Field.InvH))), 0, f.Field.Ny-1)
//originCellIdx := cxi*f.Field.Ny + cyi
//find fluid cell for particle
for i := range f.Particles {
p := &f.Particles[i]
//xi := utils.Clamp(int(math.Floor(float64(p.Position.X*f.Field.InvH))), 0, f.Field.Nx-1)
//yi := utils.Clamp(int(math.Floor(float64(p.Position.Y*f.Field.InvH))), 0, f.Field.Ny-1)
//
//dx := originX - px
//dy := originY - py
dx := p.Position.X - originX
dy := p.Position.Y - originY
dist2 := dx*dx + dy*dy
if dist2 < radius*radius || dist2 == 0 {
continue
}
dist := float32(math.Sqrt(float64(dist2)))
newx := originX + dx*radius/dist
newy := originY + dy*radius/dist
p.Position.X = newx
p.Position.Y = newy
p.Velocity.X = 0
}
if p.Position.X > maxX {
p.Position.X = maxX
p.Velocity.X = 0
}
if p.Position.Y < minY {
p.Position.Y = minY
p.Velocity.Y = 0
}
if p.Position.Y > maxY {
p.Position.Y = maxY
p.Velocity.Y = 0
}
}
@@ -348,8 +371,8 @@ func (f *Fluid) TransferVelocities(togrid bool) {
for i := range f.Particles {
x := f.Particles[i].Position.X
y := f.Particles[i].Position.Y
xi := clamp(int(math.Floor(float64(x*h1))), 0, f.Field.Nx-1)
yi := clamp(int(math.Floor(float64(y*h1))), 0, f.Field.Ny-1)
xi := utils.Clamp(int(math.Floor(float64(x*h1))), 0, f.Field.Nx-1)
yi := utils.Clamp(int(math.Floor(float64(y*h1))), 0, f.Field.Ny-1)
cellnumber := xi*n + yi
if f.Field.CellType[cellnumber] == CellTypeAir {
f.Field.CellType[cellnumber] = CellTypeFluid
@@ -380,8 +403,8 @@ func (f *Fluid) TransferVelocities(togrid bool) {
x := p.Position.X
y := p.Position.Y
x = clamp32(x, f.Field.H, float32((f.Field.Nx-1))*f.Field.H)
y = clamp32(y, f.Field.H, float32((f.Field.Ny-1))*f.Field.H)
x = utils.Clamp32(x, f.Field.H, float32((f.Field.Nx-1))*f.Field.H)
y = utils.Clamp32(y, f.Field.H, float32((f.Field.Ny-1))*f.Field.H)
//find cell components neighbouring x,y
x0 := min(int(math.Floor(float64((x-dx)*h1))), f.Field.Nx-2)
@@ -513,15 +536,15 @@ func (f *Fluid) UpdateParticleDensity() {
h1 := f.Field.InvH
h2 := 0.5 * h
clear(f.particleDensity)
clear(f.ParticleDensity)
for i := range f.Particles {
p := &f.Particles[i]
x := p.Position.X
y := p.Position.Y
x = clamp32(x, h, float32(f.Field.Nx-1)*h)
y = clamp32(y, h, float32(f.Field.Ny-1)*h)
x = utils.Clamp32(x, h, float32(f.Field.Nx-1)*h)
y = utils.Clamp32(y, h, float32(f.Field.Ny-1)*h)
x0 := int(math.Floor(float64((x - h2) * h1)))
x1 := min(x0+1, f.Field.Nx-2)
@@ -536,32 +559,32 @@ func (f *Fluid) UpdateParticleDensity() {
sy := 1.0 - ty
if x0 < f.Field.Nx && y0 < f.Field.Ny {
f.particleDensity[x0*n+y0] += sx * sy
f.ParticleDensity[x0*n+y0] += sx * sy
}
if x1 < f.Field.Nx && y0 < f.Field.Ny {
f.particleDensity[x1*n+y0] += tx * sy
f.ParticleDensity[x1*n+y0] += tx * sy
}
if x1 < f.Field.Nx && y1 < f.Field.Ny {
f.particleDensity[x1*n+y1] += tx * ty
f.ParticleDensity[x1*n+y1] += tx * ty
}
if x0 < f.Field.Nx && y1 < f.Field.Ny {
f.particleDensity[x0*n+y1] += sx * ty
f.ParticleDensity[x0*n+y1] += sx * ty
}
}
if f.particleRestDensity == 0.0 {
if f.ParticleRestDensity == 0.0 {
var sum float32 = 0.0
numFluidCells := 0
for i := 0; i < f.Field.Nx*f.Field.Ny; i++ {
if f.Field.CellType[i] == CellTypeFluid {
sum += f.particleDensity[i]
sum += f.ParticleDensity[i]
numFluidCells++
}
}
if numFluidCells > 0 {
f.particleRestDensity = sum / float32(numFluidCells)
f.ParticleRestDensity = sum / float32(numFluidCells)
}
}
}
@@ -602,9 +625,9 @@ func (f *Fluid) SolveIncompressibility() {
//divergence -> we want this to be zero
div := f.Field.U[right] - f.Field.U[center] + f.Field.V[top] - f.Field.V[center]
if f.particleRestDensity > 0.0 {
if f.ParticleRestDensity > 0.0 {
var k float32 = 1.0
var compression float32 = f.particleDensity[i*n+j] - f.particleRestDensity
var compression float32 = f.ParticleDensity[i*n+j] - f.ParticleRestDensity
if compression > 0.0 {
div = div - k*compression
}
@@ -624,3 +647,7 @@ func (f *Fluid) SolveIncompressibility() {
}
}
func (f *Fluid) ToggleShape() {
f.Block = !f.Block
}