Felician Lepadatu | RESEARCH | Cave Flooding

Latest Result:

To do list:

import/export mesh settings, scale, units, file formats, optimizations for complex geometry
simulation techniques, partitions, network sim, switches
solid dynamics inside fluid and interaction
fluid mesh building and export options
optimize mesh or surface building
shading
details: bump, ripples, foam, wet map, density map + shading
render passes + light setup
comp + nuke gizmos

01. import/export mesh settings, scale, units, file formats, optimizations for complex geometry

3D Studio Max units scale 1 unit = 1 meter
import scale in RealFlow 1
scene size for simulation grid inside 3DSMax aprox. 30 meters X 30 meters
the geometry container can be single sided but the normals have to be toward the fluid
the geometry container has to be collapsed to poly, triangle faces, max 7K triangles (we choose this value arbitrary and it seems to work both ways – quality and size wise/speed), pivot centered on 0,0,0 world, pivot aligned to world. this is initial state for geometry in order to reference everything by this.
the object can be exported as OBJ or SD from inside 3DSMax. I exporting SD, single frame, selected object.
the object can be imported back from RealFlow as SD or OBJ. The SD import works great and does not affect pivot or scene placement. The condition is not to have the same named object inside 3DSMax.
the SD export object can be activated under Export Central inside RealFlow.
if the export option is OBJ, then you have to mirror it on Y axes with the offset -2*Y_value (keep in mind initial state mesh).
RealFlow fluid meshes export as bin’s and it come as ‘flipped’ inside 3DSMax.
scale -Y and it snaps into place.

Mesh optimization results:

Updated low resolution cave mesh (for fluid simulation). Decimated from 40k to only 4k faces.

Shape curvature deviation is kept between 4% and 16%. Planar surfaces were decimated separately to keep the poly count to a minimum.

Dark green areas show original dense topology. Brighter colors show low res version.

Triangle spread and topology.

02. initial settings for fluid, density, viscosity, no of particles

1. Scale 1 unit = 1 meter (3dsmax), scale 1.00 (realFlow)
2. Realflow Sim FPS 25fps
Current Settings

Resolution 0.1 => 300k particles to fill the whole volume
Density 1000
int pressure 1
ext pressure 1
Viscosity 3
Surface Tension 0
Max Particles 5000k

Conclusion: – to be simulated
Last sim looked good but particles were too scarse so mesh ended up with low definition.

Production Settings

Resolution (all fluids) 1 => 1400k particles to fill the whole volume
Max particles count (all fluids) => 5000k
Water density = 1000
ReWater density = 1000
Foam density = 780
Spray density = 700
Scene scale = 1
Sim time for 600 frames = aprox. 52h

03. simulation techniques, partitions, network sim, switches

The particle emiters are:

Water – density 1000
ReWater – density 1000
Foam – density 780
Spray – density 700

The script has been tested on a 1.0 RF scale

Event script: waveFoamSprayEvent v1.0 from nextlimit website – all the copyright to the owner.

What the event script does:

cycles trough every water particles and tests for pressure, velocity and collision.
when the water particles values tested are inside the treshold limits stated by us, we copy the particle from the water emitter to the foam emitter.
cycles trough every foam particles and tests for age and height,
when the foam particles values tested are inside the treshold limits stated by us, we copy the particle from the foam emitter to the rewater emitter.

We modified the script to get the ReWater particles back to Water particles after given time, in order to end up with only one fluid. This is because we want to pass only one particle system to the next stage.

# Transform particles back to REwater back to WATER

particle_rewater = rewater.getFirstParticle()

while (particle_rewater):

current_age = particle_rewater.getAge()

vel_rewater = particle_rewater.getVelocity()

pos_rewater = particle_rewater.getPosition()

if (current_age >= 2):

water.addParticle(pos_rewater,vel_rewater)

rewater.removeParticle(particle_rewater.getId())

particle_foam = particle_foam.getNextParticle()

Final result of the simulation:

04. solid dynamics inside fluid and interaction

- on hold for the time being

05. fluid mesh building and export options

First pass: one mesh (Water + ReWater)

polygon size 0.06
filters on
relaxation 0.1
tension 0.05
steps 64
radius 0.04

Export mesh as .bin file

Final result of the mesh build – rendered on mray

06. shading

Foam shading – pyrocluster and mental ray:

Use Real Flow particle cache .bin files inside 3dsmax. For shading particles I choose pyrocluster voxel renderer because of the integration with the mental ray:

3D Studio Max scale values: 1 unit = 1 meter, display metric

Pyrocluster settings for foam:

include RFparticles_foam – particle system
include 1 spot light with shadow cast on – same position as the sunlight in the scene
initial step 0.1m
color 1 = 240,248,254
color 2 = 213,221,225
illumination enable
receive shadow on
self shadows on
initial shadow step = 0.2m
override light settings on
shadow type = raytrace shadows
shape = sphere
radius 0.2m
squash 0.1
regularity 30%
velocity scale on
stretch 5.0
noise type = turbulence
density 260
size 0.2
details 3

first render of the foam particles – no upscale interpolation

clay mesh + foam particles geometry + pyrocluster