Example of insufficient TraceLevel
(Black artifacts visible)
Legal
information
Installation
Quick
start
Parameters:
BASIC
obj_pos
TraceLevel
SceneStartClock
SourceID
PreviewMode
MainColor
SmokeDens
TIME
SIMULATION
FramesElapsed
SplineFile
SplineClockStart
SplineClockStop
TRAIL
SPECIFIC
SmokeDelay
TrailLength
SIZE
SPECIFIC
InitialSize
MaxSizeInc
MaxFinalSize
EMISSION
SPECIFIC
InitEmiss
MinEmiss
MaxEmiss
Trend
APPEARANCE
SPECIFIC
Roughness
MinSamples
StartTurb
TurbIncRate
CastShadows
WIND,
ROTATION & ASCENSION
ConstAscendRate
MaxRandAscend
WindDirection
WindStrength
ConstRotation
MaxRandRot
DanceStrength
DanceRate
EFFECTS
RotationCenter
SmokeMass
EXTRA
SecondaryColor
1. SmokeGen is postcardware and thus free to use, copy and modify, provided that you send a postcard to the address specified below. Try to find a postcard with a motive that's as typical for your hometown(or area) as possible! :-)
2. SmokeGen may not be sold or used commercially without permission by the author.
Send your postcard to:
Mikael Carneholm, SA4
IDA
Högskolan i Borås
Allégatan 1
501
90 BORÅS
SWEDEN
POV-Ray(tm) and Persistence of Vision(tm) are registered trademarks of the POV-Ray Team(tm)
Extract all the files contained in the root of the zipped file to one of the
directories (folders) in your POV-Ray
library path (as for example, the
default include directory). If you don´t know what they
are, open your
POVRAY.INI. If you have a PC running Windows95/98 or WindowsNT, they
probably look something like this:
Library_Path=C:\POV-Ray for Windows\include
If you want to try the examples, also extract the example files with their
full paths
to a directory of your choice (if using pkunzip in DOS mode, type
"pkunzip -d smokegen.zip" to extract with full paths).
The most basic usage is to just declare one variable, called obj_pos and thereafter include the SmokeGen.inc file.
Example:
#declare obj_pos=<0,0,clock*20>;
#include "SmokeGen.inc"
That´s it! The SmokeGen include file (and POV-Ray) takes care of the rest,
and smoke will
follow the car, airplane, rocket etc.
The variable obj_pos is the postition of the object that is generating the
smoke. I.e, if
you have an object that you want to animate, declare some
clock dependant conditions that
control the value of the variable, and then
make your object translate with that value.
This way, the smoke "derives"
the position from the object automatically.
Example:
#if( (clock>=0) & (clock<0.5))
#declare obj_pos=<0,0,clock*20>;
#end
#if( (clock>=0.5) &
(clock<1.0))
#declare
obj_pos=<0,clock*20,10>;
#end
.
.
object
{
your_object //previously declared in the file
translate obj_pos
}
#include "SmokeGen.inc"
NOTE: The main thing is, obj_pos must be declared before SmokeGen is included.
obj_pos
Type: Vector
This is the most important variable in SmokeGen, as it controls:
1. If a
smokesource is active
2. Where it is located
As long as obj_pos is
declared, smoke will be generated at (from) that position. Once generated, it
will live as long as the parameters tells it (and SmokeGen.inc is included).
Example:
#if(clock<0.5)
#declare obj_pos=<5,0,0>;
#end
#include "SmokeGen.inc"
This will create a smoke source that is active at position <5,0,0> while clock is less than 0.5. After this, the smoke will live on and ascend, rotate etc. as long the parameters allows it to exist.
TraceLevel (Previously called
MxTrLvl)
Type: Integer
A little "bug" in POV-Ray is the black
artifacts that can appear when light passes though
many media objects along
its way. This phenomenon is illustrated below.
To correct this, use this
variable to get rid of the artifacts. This may vary from scene to
scene
depending on how many objects the camera looks "through", but if you at some
point have [n] smoke
elements with smoke density [m] along an imaginary straight line
from
the camera, you will need a trace level of [2*n*m+1].
Note: It's not necessary to do this calculation. If you get black artifacts
in your scene, just
increase TraceLevel until the artifacts disappear.
Example of insufficient TraceLevel
(Black artifacts visible)
Problem solved by increasing TraceLevel
(No more visible artifacts)
SceneStartClock
Type:
Numerical
This value is used to re-write the files that SmokeGen
reads/writes, and it´s important
that you give this variable the same value
as the Initial_Clock (+KI). If you don´t,
you may experience "ghost smoke"
from previous runs.
SourceID
Type: Integer
When doing an animation you may want the smoke from one source to drift away
in one direction, smoke from another to to drift away in the opposite direction
and a third should stop generating smoke halfway through the animation(while not
stopping the smoke already generated by that source from drifting away in the
same direction as previously). To do this, SmokeGen must know which smoke from
what source to affect when you call it. This is done by declaring different
source ID:s for different sources, and including SmokeGen once for each source
in the scene.
Also note that the first source doesn´t need to be ID:d, as it is always considered as source 1.
PreviewMode
Type:
Integer
Since media (previously called halo) can take long time to
render, there are 2 preview
modes that renders the elements as:
1. spheres with gradient pigments ("wireframes")
2. spheres
with plain pigments
If you need to see the rotation of the smoke, use mode 1. If not, use mode 2.
(Mode 0 is
"real" mode, with smoke rendered using media.)
[PreviewMode=0]
[PreviewMode=1]
[PreviewMode=2]
MainColor
Type: Vector
This vector describes the main color of the smoke, the one that is emitted
with the intensity
of the emission value. Any 3-dimensional color vector
will do, except <0,0,0> that will produce invisible smoke.
Note: To
achieve black smoke, use <-1, -1, -1>
[MainColor=<0,0,1>]
[MainColor=<0,1,1>]
[MainColor=Red]
SmokeDens
Type: Integer
Accepted values: 1-10
To control the density of the smoke,
increase/decrease the value of this variable. (Note the relation
SmokeDens<->TraceLevel, described in TraceLevel.)
Also note that when increasing density, the rendering time increases about
the same amount....
[SmokeDens=1]
[SmokeDens=5]
FramesElapsed
Type:
Integer
To simulate elapsed time, you can use this variable to generate
smoke that has been created during x amount of time (n number of frames). This
means, if you set FramesElapsed=10, you will see 11 smoke elements on the first
frame (10 elements created by the previous frames).
There are two "modes" when using time simulation:
Mode 1 is the "static source" mode, i.e obj_pos is constant during all "frames", and wind and other translating effects is used to achieve some sort of smoke pillar.
Mode 2 is the "spline trail" mode, where a spline file is used to define the positions through time (useful when animating an object that moves along a spile curve). Note: currently, this mode requires that splines are defined using Chris Colefax's Spline generator include. The segment of the curve that should be "filled" is defined by SplineClockStart and SplineClockStop, going from SplineClockStart to SplineClockStop with a density of [FramesElapsed] number of elements.
To use mode 1, just declare FramesElapsed and leave out either one of
SplineFile, SplineClockStart, SplineClockStop.
To use mode 2, declare
SplineFile, SplineClockStart and SplineClockStop as well as FramesElapsed.
SplineFile
Type:
String
This variable tells SmokeGen the name of the file that defines
your spline curve. This file has to be of the type that is used by Chris
Colefax's Spline
generator include, i.e, it has to return the vector spline_pos in order to
work. (An example would be SplineFile="MySpline.spl")
SplineClockStart
Type: Float
SplineClockStart defines where on the spline curve
the elements starts to be generated - to use the very start of the curve, use
SplineClockStart=0.
SplineClockStop
Type:
Float
SplineClockStop defines where on the spline curve the elements
stops to be generated - to use the very end of the curve, use
SplineClockStart=1.
SmokeDelay
Type:
Integer
SmokeDelay determines the position in the position history where
the smoke starts appearing. Generally, smoke appears a bit behind the object,
not
right where it is "at the moment". Use this variable to determine the
distance.
TrailLength
Type:
Integer
This can be used to cut off a trail at a desired length. Below
are two animations showing the difference between using TrailLength and not
using TrailLength.
[NoTrailLength
used]
[TrailLength=10]
InitialSize
Type:
Numerical
Determines the initial size(radius) of each smoke element.
MaxSizeInc
Type:
Numerical
Determines how much each element can grow from frame to frame,
in pov units. For example: with MaxSizeInc set to 0.5, an element with a size of
0.5 at frame one will at most have a size of 1.0 at frame two.
MaxFinalSize
Type:
Numerical
Constrains how much the elements can grow. When an element
reaches this size, it will no longer grow with the amount determined by MaxSizeInc.
Emission is the property that is refered to as opacity in some programs. Formula is [E=InitEmiss+Trend*FrameCount]
InitEmiss
Type:
Numerical
This variable controls the initial
emission(opacity) of the smoke. See the images below for demonstration.
[InitEmiss=0.5]
[InitEmiss=1.0]
[InitEmiss=2.0]
[InitEmiss=5.0]
MinEmiss
Type: Numerical
This variable determines the minimum emission an element can reach,
when using Trend
to alter the emission over time. (If MinEmiss is set to 0, the elements will
fade out totally) Below are two example animations that demonstrates the
difference between MinEmiss=0.5 and MinEmiss=0.
NOTE: MinEmiss must be less than InitEmiss for Trend to have effect.
[MinEmiss=0.5]
[MinEmiss=0]
MaxEmiss
Type: Numerical
This variable works like MinEmiss,
just the other way around. It controls the maximum emission an element
can reach, when using Trend
to alter the emission of the elements over time.
NOTE: MaxEmiss must be more than InitEmiss for Trend to have effect.
Trend
Type: Numerical
The Trend variable determines the development of the emission over time. A
positive value makes the emission increase, while a negative value makes the
emission decrease. An example: if Trend=0.1, the emission will increase by 0.1
units/frame. Likewise, if Trend= -0.1, the emission will decrease by 0.1
units/frame.
[Trend=0.1]
(Positive)
[Trend=-0.1] (Negative)
Roughness (Previously called
Pulverization)
Type: Integer
Accepted values: 1-10
This variable can be used to change the appearance on the rough/fine scale,
as illustrated below. This is useful specially when using SmokeGen for
generating other effects than smoke.
[Roughness=10]
[Roughness=1]
MinSamples
Type:
Integer
Especially when the smoke elements are scaled high, a certain
level of "grainyness" starts to appear. This is due to the minimum number of
samples that is set default in SmokeGen. To avoid this, increase the value of
MinSamples (default value is 1).
Note: The larger number of samples, the slower the rendering. Thus, do not set this larger than default if not necessary.
[MinSamples=low]
[MinSamples increased]
StartTurb
Type:
Numerical
Use this variable to control the initial turbulence in the
elements, that is, the turbulence right after the element has been created.
Below are some illustrations of various degrees of turbulence:
[0]
[0.5]
[1.0]
[1.5]
[2.0]
[2.5]
[3.0]
[3.5]
TurbIncRate
Type:
Numerical
TurbIncRate controls how fast the turbulence increases over
time. [TurbIncRate=0.1] makes the turbulence increase 0.1 units/frame.
Turbulence is important to get that realistic modularization of the smoke
(=twisting&fading at the same time).
This can be an alternative(or
complement) to using Trend
to achieve a fading effect.
[Usage of TurbIncRate to achieve a fading effect]
CastShadows
Type:
Boolean
The smoke can be made to cast shadows or not. [CastShadows=true] or [CastShadows=1] will make the smoke cast
shadows, while [CastShadows=false] or [CastShadows=0] will turn
shadows off.
[CastShadows=true]
[CastShadows=false]
ConstAscendRate
Type:
Numerical
This variable controls the constant movement of the elements
in the Y axis. For example, [ConstAscendRate=0.3] means
each element will be translated 0.3 units per frame in the positive Y direction.
To get a realistic smoke effect, add some random movement as well by using MaxRandAscend.
MaxRandAscend
Type:
Numerical
MaxRandAscend controls the random ascension of the elements.
For example, [MaxRandAscend=0.2] means that the maximum
random translation in the positive Y direction will be 0.2. Normally,
MaxRandAscend should be used in addition to ConstAscendRate
as a "spice" to achieve a more realistic behaviour of the smoke.
WindDirection
Type:Vector
This vector describes the direction of a (constant)
wind that it blowing in your scene and thus affecting the smoke. Following this
package you should find the file "DefWinds" containing 8 pre-declared
winddirections (N,NE,E,SE,S,SW,W,NW), made with the definition Z+ =North, X+
=East, Z- =South and X- =West.
NOTE: For the wind to have effect, a WindStrength
has to be declared.
Example 1: (using the default winds)
#include
"DefWinds"
#declare WindDirection=N;
Example 2: (declaring your own wind direction)
#declare
WindDirection=<0.3, 0, 0.8>;
[Without
wind]
[With wind]
WindStrength
Type:Numerical
For a WindDirection
to have effect, a WindStrength also has to be declared. For example, if you
declare WindDirection=N (which equals <0,0,1>) and give WindStrength the
value of 0.3, the total wind will be blowing with <0,0,0.3> units/frame.
Formula is [total wind=WindDirection*WindStrength]
ConstRotation
Type:
Numerical
This variable controls the constant rotation of the smoke. The
value determines the number of degrees each element rotates each frame, i.e
[ConstRotation=5] gives 5 degrees rotation per frame.
Rotation is useful both for smoke after moving vehicles and for smoke from
static objects. The rotation is done about the normal between the elements(see
illustration below)
Below are two animations that show the same scene, one where rotation is used
and one where no rotation is used.
(Note: Both scenes use MaxSizeInc to
achieve a slight growing effect, which is what makes the smoke "live" in the
no-rotation scene.)
[With]
[Without]
MaxRandRot
Type:
Numerical
Apart from using constant
rotation, some random rotation can also be used. Type of rotation is the
same as for the constant type, i.e degrees per frame about the normal between
the elements.
General info: New to version 1.2, is DanceStrength and
DanceRate that can be used to create a wriggling, winding effect.
The effect depends on the WindDir
vector, i.e the "dancing" will be in the (+/-)WindDir direction.
DanceStrength
Type:
Numerical
DanceStrength determines the width of the oscillation, in POV
units. Be careful though, as the distance accumulates for each full oscillation
cycle. Good starting values could be 0.001 to 0.01 (dependant on scene scaling
of course).
[DanceStrength=0.006]
[DanceStrength=0.012]
DanceRate
Type:
Numerical
DanceRate controls the time between each oscillation peak, i.e
the number of peaks during a period of time. A high value thus gives a
slow oscillation, while a low value gives a quick oscillation.
[DanceRate=10]
[DanceRate=1]
RotationCenter
Type: Vector
RotationCenter
defines the point that the object is rotating about. For example, if you declare
a cube at <0,0,0>, rotate it about <0,0,0> and then translate that
object to <0,3,1> it will appear to be rotating about <0,3,1>. Thus,
declare RotationCenter as <0,3,1>.
SmokeMass
Type: Numerical
To control how far away the smoke
will be thrown, use SmokeMass. A higher value gives long distances, while a low
value gives short distances. Note: The distance is depending on how fast the
object is rotating, as well. Formula is [angle*mass]
[Low
SmokeMass]
[Higher SmokeMass]
SecondaryColor
Type: Vector
As an option, the
secondary color of the media contained within the elements can be controlled by
SecondaryColor.
[SecondaryColor=<0,0,1>]
Glossary:
Smoke element: A sphere
that is used as a container for the media.
© Copyright Mikael Carneholm 1999