Happy Spring Festival!

Xianghui Xie, Chengjiangrong Peng

Concept

Spring festival, or Chinese lunar new year, the most important festival for Chinese, is comming soon. Like Christmas, the lunar new year is a festival for family reunion. This year, we cannot go home to experience the real festival scene but we can build it in our fantastic graphics world! The 3D scene is designed based on our memories about Spring Festival: firecrackers, red color, couplets, goodwishes, and next year belongs to ox. With this new year scene (although some words in Chinese), we wish you all the best in the year of ox!

Volume Scattering

We use the Volume scattering to mimic the fog and light created by the firecracker, we implement an isotropic medium, which contains out scattering, attenuation and in scattering.
The medium not only influences the view ray's radiance but also the light, we use ray marching to calculate the lighting effects of medium object. The Medium class we implemented is similar to a primitive in concept, but it has different intersection with ray.
Here I will show some interesting tests: we can add emissive object, change scattering parameters to alter the appearance of the fog.

Environment Mapping

We use Sphere Environment mapping to create a Sphere that reflects a snow view, without actually buiding a snow environment in our scene. The original snow view image is shown on the right.

The flying fire rocket

Fire rocket should be flying in the air. We add dynamics for it by implementing a moving triangle. All the triangles of this rocket mesh move towards the same direction and with a motion blur camera, the rocket can fly.

The year of ox

Each Chinese lunar new year is assigned with one of the twelve zodiac animals. And next year belongs to ox. We adapted the cow mesh from assignment 3 and 'dress' it up with an image full of good wishes written in Chinese. This cow will bring with good wishes to start the new year.

Elements of the Spring Festival

On the left side of the golden sphere is a sphere textured with an image of a Chinese character: 福. It means good luck in English. The image attached to the front door represents the festival tradition: stick couplets to both sides of the door. Such a decoration expresses happiness and hopeful thougths for the coming year.

Others

The golden ball is a sphere with combined material of Phong and Lambertian. We use five arealights to bring radiance to this scene: two disc arealights pointing straight down. One disc arealight pointing towards the building and two ground lights to add a little radiance to the ground balls.

Implementation details

We use Blender to setup positions, textures and scales of the scene. The Volume Scattering: ray marching is implemented in volumetracer, the accompanying classes are Medium and IntersectionM .
The Sphere environment Mapping is implemented in Envmapper. Motion blur effect is implemented in MovingTriangle and movingblurcamera. We also use OpenMP library to enable multithread rendering.

Statistics

In total, 124,122 faces are loaded.

With a BVH acceleration structure, we can render the low resolution image in 30 minutes (50 supersamples) and the high resolution image (20 supersamples) in 3.23 hours (Intel Xeon E5-2680).

Credits

The website template is from shutterstock

The 3D meshes are downloaded from free3d and Turbosquid