Summer dreaming.

for the Rendering Competition 2020

by Hendrik Junkawitsch


'Summer will end soon enough, and childhood as well.'

~ George R.R. Martin in Game of Thrones.

Summer dreaming.

While I was sitting at my desk somewhere in the middle of Saarbrücken my thoughts wandered away from raytracing and coding. Wistfully I thought back to the summer where everything was different. The hot summer days with good friends and a few cocktails for cooling ourselves down.

Now ‘winter is here’ and childhood is gone. But why should we be sad about it?

I realized that I could just bring some of the warmth of these cocktail summer days into my apartment, while cold rain was drumming on the windows.

And thus, the idea was born to create a warm summer themed scene with cocktails and a lot of nostalgia and hope for better days.

It was time to give the sketch some shape.

To model my scene, I used the free modeling/rendering software Blender.

I tried to find the right assets that would fit the overall theme of my scene. I completely redesigned the room with a new table, flowers, plants and a few things you need to make yourself some cocktails. I ended up modeling the water spill and the ice cubes myself. In total the scene includes 1.7 million faces.

A lot of trial and error…

But finally I got a good result with a summery atmosphere.

Special Materials

I used complex glass, steel, fuzzy mirror and water materials for a realistic image.





The water is just a GlassMaterial but with a modified refraction index. Additionally I had to ignore the water spill in the light computation in the integrator such that the shadow ray can reach a light source.

Bump Mapping

Bump Mapping to give the texture micro structure and make the picture even more realistic. Use the slider to see the difference.


To achieve a balanced lighting and to avoid hard shadows I only used two area lights.

I changed the color of the lights to a yellowish white to create a warm and peaceful environment.

I added a light emitting plane with an emission map to simulate a blue sky and green fields outside.

One area light was placed directly opposite to the window to create a strong reflection on the glass to overexpose the window.

Multithreading and Sample Maps

To make use of the full power of my cpu I implemented parallel rendering. By using per-pixel parallelism I achieve almost perfect workload of all threads.

This allowed me to keep all 16 threads of the AMD Ryzen 3700X running for the whole rendering time. Resulting in over 10 times faster rendering speeds.

No Multithreading

41.98sec (480x270 / 1 Sample)


3.98sec (480x270 / 1 Sample)

I realized that even with 700 Samples per pixel the complex glass structures are not looking as good as i hoped them to.

Adding Sampling Maps allowed me to render different parts of the image with different sampling numbers. With this approach i was able to focus the rendering power on glass structures and not waste it for simple materials.

Even though the difference is small, it is definitely visible that the glass materials look less noisy in the image with Sample Mapping.

Use the slider to see the difference.

With Samplemap

500 base samples and glass with 2500 Samples; 10.769h

Without Samplemap

700 Samples; 10.3h








500 - 2500

All facts:

  • Scene
    • Faces: 1.730.373
    • Ray Tracing depth: 6
  • Machine
    • AMD Ryzen 7 3700X (out of the box) / 8 cores / 16 threads
    • 16GB RAM 3200MHz
  • High resolution image:
    • Resolution: 1920x1080
    • Samples: 500 - 2500
    • Rendering time: 10.769h
  • Low resolution image:
    • Resolution: 480x270
    • Samples: 7000
    • Rendering time: 6.35h