Our scenes inspiration originates from the philosophy of contrast. The idea was to convey a comparison between two extremes inside the same picture, thereby challenging our artistic sense as well as the capabilities of our ray-tracer. That is why we split up the scene into two parts, with earth being the connecting center piece.
On the left side of the image we see an abstract representation of carbon fuels in form of diamonds, while the other side depicts one of the most abundant sources of renewable energy - solar energy. We see this picture as a representation of the Crossroads humanity is standing at right now - between the destructive, but lucrative use of fossil fuels and the difficult introduction of new, but regenerative energy sources.
Even though diamonds look glamorous and alluring by nature, the concept they represent will lead to a destroyed environment in the long run. The effects are depicted by the use of red lights, which are naturally perceived as a sign of danger, and the emptiness of the background, signalling the unsustainability of fossil fuels. The left side of earth is plunged into darkness and even though we can see that there are lights shining in populated areas, it does not look like an earth we would like to live on.
In contrast, we see ordinary looking solar panels on the right side,
but using them will result in a brighter and sustainable future,
indicated by a well lit scene and the ongoing presence of solar
panels in the background. The earth looks healthy, with the ability
to nurture life, which is shown by the presence of a small
plant on this side of the scene.
The reflection of earth and its surrounding stars on the solar panels
indicates the future potential of this energy source to
enable humanity to "reach for the stars".
The diamonds cast "caustic" shadows, which we achieved by recursively tracing a shadow ray intersecting with the diamonds. This effect, in combination with the refractions and reflections on the diamonds surfaces produce complex light patterns.
We were able to create a clear, contrasting border using two infinite planes right at the center of our scene. By directing the planes normals to face in opposite directions (parallel to the image plane), they curtain the effects of the two scenarios from one another, while staying invisible to the camera.
On top of a surface texture for both halfs of the globe, we are using a lambertian material with a split emition texture on the left side, making it possible to see the nightlights emitted by earth only on the dark side of the scene.
We use two area lights with different colors directly above the globe to light up the scene and produce smooth shadows. To increase the illumination, we used two directional lights parallel to the floor, pointed towards earth. Because of the planes splitting the image center, the effects of lights on one side of the scene can not be seen on the other side.
Not only are the solar panels positioned and rotated in a way, that they reflect the earth into the camera, but we can also see the surrounding stars in the reflection. This was achieved by putting a starlight texture onto the splitting infinite plane facing the right side of the scene.
Both the low resolution (470x270) and the high resolution (1920x1080)
images were generated
using 1000 samples per pixel. This fact combined with the amount of
recursive
ray-traces produced by the glass material and caustic shadows
of the diamonds, and the mirror material of the solar panels, forced
us to introduce parallelisation into the framework.
We extended the Renderer class to utilise multiple threads (depending
on the capabilities of the hardware) to calculate the radiance
of multiple pixels at the same time.
Combined with optimisations introduced during the lecture (Bounding
Volume Hierarchies and instancing), we managed to reduce
the rendering time to less than four hours on an Intel-i7
(duo-core, 3.00 GHz) processor.
One of the main features of our scene are the diamonds, which we modeled ourselves using Blender. We used three instances of the same model to rotate and position the diamonds. The model consists of 50 faces, each with a glass material mapped onto it, using the refractive index of a diamond (~2.4).
Earth: The earth is a primitive sphere with a
Combine-Material mapped onto the surface using spherical mapping.
Solar panels: We used Quad primitives to
create a single solar panel, mapping a Combine-material onto
the main surface utilising planar mapping. We then used instancing
to create, position and rotate the array of solar panels as seen in
the scene.
The Combine-material is
made up of a mirror material and a Phong-material displaying a texture,
using similar weights for both materials.
Plant: Because it is difficult to find free, highly defined models of small plants, we used
a simple model and mapped a constant green texture onto it. Because the
scene is meant to be surrealistic, we felt that the lack of details on the
plant did not interfere with the overall composition of the image.
Created by Osman Ali Mian and David Liebemann for the Computer Graphics Rendering Competition, WS17/18. A reasonable amount of rays were refracted and reflected during the making of these pictures.
