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Tutorial: Study
Hall Interior
(lasted updated 03.01.2003)
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Scene]
This is
a brief tutorial for lighting an interior scene to
be rendered with VRay 1.09n Advanced. It is
not intended as a comprehensive tutorial on modeling,
texturing or lighting of an architectural scene. The
aim is to outline one particular workflow for setting
up lighting with VRay, and should be viewed only as
a guide for approaching similar interior scenes.
Additive
Lighting
It
is always helpful to approach the challenge of lighting
a scene with a strategy in mind. In this scenario,
we'll use an additive approach.
This approach usually begins by starting in darkness
and then progressively adding lights, one at a time.
Lights are only added after the settings for the existing
lights are satisfactory. This allows us to keep track
of how each light contributes to the scene, before
adding new ones. This also avoids having any unnecessary
lights in the scene, that may cause unexpected results
or increase render times. I generally start with Sky
light, then add Sun light and finally, additional fill
lights if required.
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PREPARATION & SETUP
1. Start by hiding all
the glass before calculating the Irradiance
Map. Not only will this allow more light to pass through,
it will also greatly speed up future test renders.
2. Set the render size to 400x300, and Image
Sampler AA to Fixed: Subdiv=1. At this early stage,
we want fast feedback, so the test renders can be small
and jaggy.
3. Under Advanced Irradiance Map Parameters>Mode,
make sure Bucket mode is checked. The
render is divided into regions or "buckets" and
each become visible when completed.
A good size for buckets is 128x128 pixels. I
also change the Render Region Sequence often
while I'm working, so that I can see the area that
I'm interested in first. For the initial test renders,
I am mainly concerned with the light reaching the back
wall, so I set the bucket sequence from Left>Right.
4.
In the Render Dialogue Uncheck Global Switches>Reflections.
Reflections add unnecessary samples to the IR map based
on the color threshold setting.
5. Set Indirect Illumination (GI) to On.
Use Irradiance Map Presets>Low.
Make sure Show calc. phase is checked to
see the IR map being calculated and where samples are
taken.
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SKYLIGHT/ENVIRONMENT
LIGHTING
1.
Create an Omni light and turn it Off.
This overrides the default lights.
Turn on Environment>GI Environment (Skylight).
2. Make sure Overide MAX's is checked.
3. Select a light blue colour, eg. R173 G208 B255 and
set the Multiplier=4.0.
The indirect lighting is a bit too dark. We have 2
options:
i) increase the Skylight Multiplier or
ii) use Color mapping option in the render dialogue.
Color Mapping allows limited control of the contrast
between bright areas and dark areas of the image.
4. In this case, we'll use Color mapping since
the external areas have enough illumination and we
only want to brighten the interior illumination. Set
the Dark multiplier to 2.0.
Tip: A
handy
trick
is
to
reuse
a Saved
IR
map while
tweaking
the
color
mapping
multipliers.
However,you
can
only
save
an
IR
Map
calculated
using Single
mode and
not Bucket
mode.
In
future,
VRay
will
have
it's
own
Virtual
Frame
Buffer
which
will
allow
you
to
adjust
Color
Mapping
values
interactively.
From
the
help
file:
The
color
mapping
parameters "control
how
the
color
values
are
processed
before
they
are
written
to
the
output
buffer.
Color
correction
can
be
very
useful
for
indoor
or
poorly
lit
scenes
-
you
can
get
a
good
image
without
increasing
light
and
sky
multipliers.
Type -
the type of color correction. Currently the only
supported type is Linear multiply which will simply
multiply the colors by a value based on their intensity.
(A Logarithmic algorithm similar to Lightscape
would be alot more useful)
Dark mutliplier - the value that dark colors
will be multiplied by. For indoor or poorly lit scenes,
you may want to increase this value to get more light
in dark areas.
Light multiplier - the value that bright colors
will be multiplied by. Normally you'd leave this to
its default value of 1.0 which means that bright colors
will not be altered.
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SUNLIGHT
1. Create a Sun System.
Sunlight
Settings:
Color: R255 G251 B237
Multiplier: 3.0
Shadow: On - VRay Shadows
2. Adjust the Sun system so that some direct light
enters the interior spaces. Turn Off Indirect illumination
(GI) calculation to reduce render times. GI is
not necessary since we only want to see where direct
sunlight penetrates into the interior space.
The combination of Sunlight (Direct) and Skylight
(Indirect) provides enough overall illumination
for the interior. However, the render seems to have
too much blue from the Skylight.
The Skylight is dominant because of the low multiplier
value for Secondary bounce. In order to increase the
Indirect Illumination from the Sunlight, set the Secondary
Bounce Multiplier=0.7
Note: This
setting is different to adjusting color mapping
multipliers. Color map settings affect the brightness
of an image based on intensity before outputing
to the VFB, whereas changing the GI multipliers
affects the light contribution of each bounce during
IR map calculation. Therefore, changing the bounce
multipliers requires a recalculation of the IR
map, whereas color mapping can reuse a saved IR
map.
Adjusting
Color
Bleed
from
Objects
There
are
large
areas
of
timber
surfaces
in
this
space
which
would
make
the
space
a
bit
warmer
than
what
we
have
at
the
moment.
In
order
to
simulate
this
warm
bounced
light
from
the
timber
surfaces,
we
will
increase
the
Generate
GI
Multiplier
on
all
objects
with
the
timber
material.
1.
Select
all
the
objects
in
the
scene
with
the Wood1 material.
2.
In
the
Render
Dialogue,
click System>Object
Settings...
3.
The
objects
with
the
Wood1
material
should
already
be
highlighted
in
the Scene
Objects list.
Change
the Generate
GI to 1.5.
The
effect
is
very
subtle
but
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