My place in the sky

von Kai Karren

Concept

My idea was to create my favorite place at night time which is a glade in a forest at night. Because in an cloudless night it looks absolutly beautiful. Which resulted in this image called "My place in the sky". I wanted to create a scene with nice effects and an overall good look and I also tried not to escalate too much with polygon size which worked out not as good as planed (around 55.000 triangles). I also wanted to include some spheres made of mirror material because I discovered by playing around with some concepts that they can create a really nice effect. In addition they also enlarge the scene which creates more space to use with it`s pros and cons. I also wanted to have an good looking environment / sky image. Furthermore the ground of the scene should look like grass which was hard, but finally I managed to create an acceptable result using perlin noise. Because a glade alone with the mirror spheres looked to lonely I decided to add a wooden table and 4 wooden chairs to offer an exhausted walker a place to rest. In addition the mirror spheres could symbolise raindrops or the same scene in a parallel universe because each sphere shows a miniature version of the scene. If you look carefully you can also see a little hommage to the teapot in a stadium problem from the lecture in the spheres.

Development

After playing around with some other concepts the development of the final scene started with the three spheres made of mirror material and an environment map with the sky texture. Because our already implemented environment map had some performence issues with scenes with larger triangle amounts, I decided to try an alternative approach and tested an sphere with an spherical coordinate mapper applied surrounding the scene which actually produces good looking results and is up to 10 times faster in rendering for the complete scene. And yes we spend a lot of time in debugging our environment map, however the sphere approach is still faster for my scene. In addition the spherical coord mapper also allows a more flexible usage than the enviroment for transforming the texture.

The lighting in the scene is created by two really tiny fireflies with an impressive intensity. You could also call them point lights, but this term doesn't fit as good in the concept metaphor. The next step was to add the ground which should look like grass for the actual scene. After testing a disc with noise seems to be the best choice because I tried modelling grass and used grass modells, but all looked bad and or produced insane amounts of triangles. So finally I played around with perlin noise and finally I think it looks fine.

At this point the spheres seemed be be kind of alone in the scene so I thought about what could I add in the foreground? (The trees in the background should follow at the end.) I imagined some place to rest would be fitting, so I added a wooden table and four wooden chairs into the scene. Only a part of the table and one chair is visible directly the rest is visible in the mirror spheres.

Now it was time to modell the trees to finish the glade in the forest. I choose a low poly modell of a pine tree as the basic and only type of tree because other trees looked simply not as good. I also experimented with different texturing methods, used differend textures and noise. Finally I decided to choose noise. I also noticed after comparing the image on my pc monitor and on my notebook that you may have to look carefully or increase your monitor brightness to see the noise on the trees better because of the dark green noise and the realtive low amount of light at the trees in the scene. It is a night scene after all.

Finally because I remembered the teapot in a stadium problem from the lecture I added a teapot with 50.892 triangles to the scene as a hommage and to stress test the BVH. The complete scene had around 4.000 triangles before. However the rendering time on one core of an i5 6600K for the low resolution image is still under 2 min (with a BVH using the split in the middle approach). For the scene in FullHD it takes around 15 min. By working on our scenes for the rendering competition we also found some bottlenecks in our implementation which improved our rendering time especially for larger scenes around minutes. For the final image I also added a supersampling factor of 6 to improve the quality. So final rendering time is around one hour on my computer.

I would also like to thank my group mate Marc for his help during this course.

Next you can see a slide show of the development process with larger pictures.