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Sintel: 3D art technology


Now, it is the Year of Dragon. Traditionally, it is an important and successful year, the year of battles and victories. Previous 2011 passed as the typical one. During past year were done a lot of good things, such as the new patents, variety of products and continuous development of technology. However, this article will be about something else. The story will be about a girl by a name Sintel and the dragon from the short film Sintel, released by Blender Foundation more than a year ago. This film gave a huge drive to the development of the free open source 3D content creation suite Blender for the entire year 2011. Of course, this article should have been posted in the past, but it is better late than never.

A devil is hidden in the details. In computer science there is no project that could have gotten without the transition to a simplified character that does not correspond to the real world. Here are examples: illumination, hair, tissue and many other things. Therefore, there will be a lot of clickable pictures (caution, the traffic!). All models and scenes from the film are licensed under CC-BY 3.0 and are available as archives of svn project.

So, let us get started!
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The plot begins with a battle scene on the territory of dragon’s earth. We meet the main character in the mountains, when she was being attacked by the Guardian. The tired and frozen girl managed to slay him by his own spear.
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Let us return to the scene. The scene is modeled by a set of poly meshes that are made by the sculpting. The snow surface takes about one hundred megabytes. The fog is implemented as a cube with the bits.
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We will be surprised when viewing the older versions of this scene of action: there were three guards instead of one.
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Here they are: from left to right are Smith, Lao Tseu and Dark. In addition, another guard was planed inside the city. However, the only Lao Tseu passed the final casting among these 4 characters with the full rigging and facial emotions.
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Let us get back to the story. Losing consciousness she sees nearby the nomad’s tent, so after a few steps she makes the last effort and falls flat on her back ...

Here is a new scene. Sintel wakes up from a shaman’s voice, which saved and sheltered her.
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(It is image resolution of 4096x1744).

It clearly shows the effect of subsurface scattering, which is seen on the glowing fingers from the fire. The subsurface scattering is a mandatory attribute of the skin in all the scenes, and it adds a significant fraction of realism.

Here is a little bit about the Sintel. This is a very complex character with a large mesh and great textures, it is practically impossible to use it on a Core2 + 4 GB of RAM, so we will describe the Sintel Lite (a link to character). The character has about 800 000 polygons. Graphic designers have changed several times the method for creating hair at the time when character was created. There is a traditional form of hair in the form of polygons with the texture of hair. This method is widely used in the gaming industry, but even with the possibility of animation that is using the physics of soft bodies, the result is not very realistic. A much better result is obtained when using the special algorithms. However, the hair simulator was not stable at that time. During creation the simulator has been stabilized, and as a result we see the hair from the particles. The full version uses 25 000 hairs (for comparison, the average person has about 100 thousand). The motion path is determined for each hundred of hairs, so that there are seen the locks of parallel hairs. Hair’s physics is not used in Sintel, because at each scene Sintel’s hairs did by hand. Here is how the character Sintel Lite looks like before and after rendering:
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Sintel’s narrative takes us back to her hometown on a day when she met a dragon. Sintel looks for some food and holds in her hands 250 000 polygonal fruit of durian.
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Gnats are actively flying around. There can be seen only in ultra-high resolution that among the gnats is flying one tinier head of Suzanne. But now Sintel attracts the attention of sound from the roof.
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What is worth paying attention? That's right, against a background that is blurred by the effect of depth of field. Behind this effect is hiding another low-polygonal character of Suzanne.

Dragon’s wing is damaged, and a fluid simulator according to the Navier-Stokes equation calculates the motion of the blood droplets. Sintel helps to heal the wound.

Here is a new scene, showing the night departure and the dawn arrival.
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A new day is in the city. The dragon Scales runs / flies around the city, which allows making out a lot of small details. First of all, they are residents. Then Brooke and the protagonist Elephants Dream could be seen in the city. Prug came from 2005, so he is bald and even without eyebrows, because of that he has only 238 000 polygons. Also, here are 12 more random characters.
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Who would need the solar illumination? The scene with the city is illuminated by 40 light sources.
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Dragon is running after a chicken and Sintel is runinng after the dragon. At the turn Sintel is scattering fruits out of basket, each of them has 10,000 polygons. The city is pelted with the high-polygonal garbage and the statues.

No wonder that some people saw in the sky the silhouette of Big Buck Bunny against all the coincidences.
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The new scene is the temple of Ishtar city located on the mountain that is surrounded by homes.
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That's how it looks without the birds and post processing:
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Speaking of birds. Often in the modern animation could be seen a situation where a few birds flap their wings with the same frequency and phase. The reason is that the movement animation is based on the cyclical repetition of actions, such as flapping the wings and so on. In Sintel each bird is unique and flapping of the wings is determined by the angle of flight, speed, and a random component.

Here's the same temple with post processing:
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From a technical point of view here must be mentioned about the effect of Bloom, responsible for the blur of light on the bright faces of the scene. The bright background is seen here everywhere: the walls, characters and creatures. Also, it has to be noted that one object in the picture resembles the logo of Blender :).

A character of baby dragon at the time of the animation (before sculpting) has about 8000 polygons (video model). It is not a lot since it does not have the fur, hairs or particles. But after using the 4 level sculpting gets 8178 * 4 ^ 4, it is more than 2 million micro polygons.
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Here is a rough look with shading and GLSL instead of sculpting:
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The adult dragon has more polygons, which appears on the same scene (video model). If we consider 4 lever sculpting (the head sculpting compressed to 6 minutes), it gets 5 million polygons. The below will be face rendering with the high resolution. Here is how an adult dragon looks like:
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Thus, Scales was captured by the adult dragon during another walking. Sintel leaves the city walls, sneaking through the jungle (the render resolution of 4k):
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She gets through rains and storms. Here is complex fog, post processing for the rain. The Sintel is provided with the facial aging shape, which changes her hair color, skin texture and polygon mesh of face and body. Here is the video with the facial aging shape.
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She walks through the desert (the image 4k, and here is the blend-file). The light-striking effect from the sun (flare is not in the picture). At the time when the film was created the Blender did not have Dynamic Paint, so pre- drawn sand footprints appear with the help of masks. With the release of version 2.6 this effect could be gotten much easier.
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She walks through the snowy expanses. Here the vignetting effect is seen best of all: darken the edges of the frame to draw the viewer's attention to the scene of action. Also, here could be seen an artificial photo-optical noise for 3D-graphics. However, these two elements are used throughout the film.
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The history comes to the beginning, where Sintel sits the shaman”s tent and tells him the story. Here is zoomed Sintel’s face:
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In mirroring is the same person, but wounded and grown old:
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After hearing the story, the shaman indicates Sintel where is the purpose of her searching. Finally, she finds a cave. The cave like a snowy plain is made by sculpting. At the entrance to the cave is the tree, depicted on the weapons’ handle of Guardian. This is the same tree as the logo of the Sintel project.
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Hexagonal objects are the result of the bokeh effect that is a simulation of the lens aperture with six blades.
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An adult dragon eats the cow carcass. The low polygonal model of a cow has 1230 faces. After use of the five levels of sculpting a model has about 1.2 million faces. And all this (as most other objects) with three textures 4096x4096: the color, glares and bump-card.
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A baby dragon does not recognize Sintel, then an adult dragon encounters and attacks her. The simulator of particles and smoke is in all its glory:
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Sculpting on the head of a dragon in the resolution of 4k:
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During the fight the dragon knocks Sintel down, but instead of killing her, dragon hesitates, so she takes advantage of the moment and stabs the dragon fatally using her spear, and only then she sees a familiar scar and realizes that her little Scales grew up, and she just killed him... She looks at her reflection in a pool of blood, she realizes that not only the dragon has changed, but it took too much time to search for a friend.

The cave begins to collapse, and Sintel leaves it, leaving the body of a dragon there. Outside after some time dealing with her grief, she throws down the armor, weapon, and goes away. The small and lonely baby dragon follows her ...
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Here ends this story. However, those 15 minutes gave a huge drive to the development and motivation to stabilize Blender 2.5. Even today you can download a version of 2.61 with the new engine of photorealistic rendering on GPU Cycles, 3D Motion Tracking, Ocean Simulation and Dynamic Paint.

The Blender Foundation plans another short film with a codename Mango. What will we see in it? 2012 will show that!
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Pirat 24 january 2012, 16:55
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