- Assessment 2 -
Fish-bowl on a tree stump scene
Photo-realistic integration of pre-existing 3D model into an original still frame photographic background plate
WORK PROCEDURE
On set measurements and Camera data for
the background picture
The goal was to place a
pre-existing 3D model of a fish-tank into an original photographic background and
make it would look photo-realistic. The fish-bowl contains my custom 3D models
of the shield and the armour with glowing effects on it.
The scene in the composition
is situated in a forest meadow with a tree stump with a fish carved into it.
The light conditions of the
background picture are determined by the time and location of shooting.
The picture was taken in the
location of Cardiff Bute Park on Sunday the 16th of February 2014 at
16:36, it was an early spring sunny day - the Sun was low at that time,
creating long shadows and visible light beams.
The light source in the scene
- Sun - is placed on the right side of the picture – object on the right are
lit and casting shadows to the left side of the image.
Original image
and camera data:
Camera model used: PENTAX
*ist D
Dimensions: 3008
x 2008 pixels
Resolution: 72 dpi
Color representation: sRGB
F-stop f/8
Exposure time 1/125 sec
ISO ISO-200
Focal length 24 mm
No flash.
Distance of the camera from
the ground: approx. 5’8 feet
Camera positioning in Maya was
done by eye, as accurate as possible.
No lens distortion grid used,
it was not necessary for the sake of making the shot looking good.
Image scale
I rescaled and cropped the original image using Photoshop
from the original size 3008x2008 to 1920x1080 which is the resolution I wanted
to render out from Maya.
Autodesk MAYA
Camera settings adjustements
First of all I found my camera
attributes at DPreview website. I needed to find specifications for my camera
sensor, because my camera sensor was smaller (cropped) than the Maya Default
camera sensor.
Therefore I made adjustments
to Maya camera attributes according to following calculations:
Camera used: Pentax *ist D
Sensor size: APS-c (23.5 x 15.7 mm)
Inches: 0.9252
x 0.6181 inches
Original Focal
Length: 24mm
Default Maya sensor size: 36 x 24 mm
Inches: 1.417
x 0.944
Default Maya lens: 50
mm
36 / 23.5 = 1.5320
24 / 15.7 = 1.5287
1.5320 + = 1.5287 = 3.0607 / 2 = 1.5304 (average)
1.5304 * 24 (original focal length) = 36.7272
-> New
Maya lens size based on cropped sensor = 36.7272
-> Wrote
that number to Camera Attributes – Focal Length
In Maya I created a camera and
add the rescaled background image to it as Image Plane.
Placement – Horizontal, Fit to
Film Gate.
Setting the object in the scene
I created a Polygon Plane on
the ground and moved the camera around to set it to a correct place in the
scene. I applied Use Background shader to it. I set the Reflectivity little
lower, Specular color White. The purpose of this plane was to create shadows in
the scene but stay hidden when rendered.
I went through quite a lot of
struggle of figuring out how it works, about setting on and off the Primary
visibility, so the plane will not be seen in the render but it would still
provide the shadows.
I also had to shape the plane manually in order to cast the
shadow only on the top of the stump and not to exceed it.
In the beginning it looked like this when rendered:
Rendering the whole scene from Maya
At the beginning I tried to render the whole scene straight
in Maya, no Nuke compositing.
Render test1
Render test2
Render test3
Render test4 - with Ray Tracing switched off
Render test5 – Ray tracing low
Notice how the objects in the back of bowl are distorted and big
Render test6 – Ray tracing final look
Even though the last results were nice, later on I decided
to not go down that road and do it the more complicated way instead – rendering
individual layers and then composing them together.
___
COMPOSITION APPROACH
In order to make the procedure work the same way I created
the ‘Forest Armory’ scene (i.e. to create several separate render passes and
compose them together individually), I would have to hide the Reflections of all the objects in the Render Stats
attributes in the scene
That could not be done because the objects were too
complicated and made of many separate NURBS shapes which I could not merge
together. For instance the plants were
made out of hundreds of shapes – if I wanted to adjust their Render Stats, I
would have to select each one individually in the Outliner. I did not know any
other way around it.
So at the end I decided to render the Fish-bowl separately
with no shadows and then render one layer with only the shadows in it and later
compose those two in Nuke.
Render without shadows:
The shadow only:
Composition done in Nuke, using mostly basic nodes like Grade and Merge.
FINAL IMAGE
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