V-Ray 'Decisive Moment' CRASH

Thu 16th Aug 2012, by Paul Hellard | Production

CGSociety :: Winner's Tutorial

17 August 2012, by Darko Vucenik

When this competition came along, it looked like it was tailor-made for me. I just recently started to learn V-Ray, a personal quest to give myself an opportunity to push rendering and modeling skills to a new level. Inspired by the cool contest header, featuring the famous inventor Nikola Tesla (as illustrated by Toni Bratincevic), my initial ideas explored famous, world changing inventors like Einstein, Newton and their work.

However, none of the ideas featured really pinpointed a single ‘decisive moment’ so I decided to go with something different. Not a world changing event, but possibly the most decisive moment an ordinary person could face. The moment it is decided whether they will live or die. So I chose to picture the moment when a drunk driver, (let’s call him Mister Jonson), crashes in to an old telegraph pole. Is this his last moment in this world? Did he fasten his seat belt? Is his buddy ‘Death’, here just to party or is he here on business? With this in mind, I created a very rough sketch in Photoshop. The purpose of the sketch was just to check whether the composition I had in my head actually worked on paper. Well, ‘screen’, to be more precise.


Since this is the picture of a car crash it seemed logical to start building the car first. I am not much of a car enthusiast, but the old model Mini Morris was always one of my favorites. Perhaps because that’s what Mr. Bean drives. So, I Googled a bunch of reference pictures and chose the ones featuring a good side, front and back view. In Photoshop, I changed the proportions of the car making it about one third shorter and the cabin a lot taller. This gave the car a more stylized, cartoonish appearance. With these altered images as blueprints, modeling was a simple process.

I used the standard 3ds Max poly modeling features. One of the methods that made the process a lot faster is to model on the surface of another object. What I mean by that is to draw a simple curve following the curvature of the car, extrude it into a surface and then using freeform graphite modeling tools build the actual topology of the car on to that surface.

Using this method you can cut, extend and move your polys around without worrying that you will mess up the smooth curvature of the car's body. Building the mini was a lot of fun, so I modeled the whole thing despite knowing that a lot of it won't be visible in final image.

With the car was finished, I began to block in the characters. I didn't like Death’s pose in the sketch so I loosened him up a bit by tilting his head back and extending the arm holding the bottle. He is in a happy party mood. After all, he doesn't have anything to worry about. Mister Jonson on the other hand is panicking. I decided to raise his hands off the steering wheel. Positioning them in front of him looked natural, like an instinctive move to protect himself. At this stage, characters are just a fast assembly of slightly modified geometric primitives. At the same time as I'm positioning the characters, I also play with the camera looking for the right angle.

Next I made thumbnail sketches of character faces on paper (a). They are very tiny, just a two or three cm in size. Sketches can be this small because at this point I'm only looking for right overall proportions and general expressions of the face, not caring about details (yet). Using the sketches as blueprints, I block in the 3ds Max form using very simple geometry (b). Then I send the geometry to ZBrush and using DynaMesh, merge the pieces into one continuous surface for sculpting. I quickly refine the shape using various brushes, but mostly the clay build up, move and smooth. Then its back to 3ds Max for retopologizing with the Freeform Extend tool. With new topology done (c), it’s back to ZBrush for detail sculpting and poly painting (d). That is the process I used for all the character pieces.

When sculpting and polypainting all pieces was finished, I baked out color, cavity, normal and displacement maps. Various specular and glossiness maps were derived from other baked maps in Photoshop. Usually just adjusting the curves is enough with occasional overpainting.

At this point, before modeling the rest of the scene, I did a little render to check the direction in which the picture is going. Materials at this point are pretty basic. Most of them are just V-Ray materials with diffuse color and the reflection amount adjusted. Character materials are a bit further along since all the textures were already polypainted. The main lights are already in place, but more on lighting later. In Photoshop I mocked up the sky and indicated some water effects. Satisfied with the feel of the picture, I proceeded on to modeling the background and water effects.

The background is very simple. Since it will be heavily blurred in the final composite it didn't make much sense to spend much time on detailing. The sky with lightning is a painting I did in Photoshop. The ground is a plane object. The hills were created by applying the noise modifier over the soft selection. The road is another narrow plane object with bend modifier. Textures for the ground and road are procedural substance maps. In case of the ground a blend of dry ground texture, a noisy green texture for the grass and a light gray texture with distance blend for the fog effect.


Water Effects

I wanted a lot of water splashing around in the scene. Water frozen in a single moment always looks so cool. I decided to go with a simple modular approach. First I created a rough shape of the water volume. Then I would fill that volume with particles and finally mesh all of the particles in a cool looking watery blob. All it took to change the look of the splash was to move few of the source volume's vertices around or replace it with another simple mesh. To create a more broken up splash effects I modified the particle flow setup a bit. I reduced the number of particles in the volume and added a spawn event. That created little trail after every particle. To randomize the look I added turbulent wind. The rest of the splashing water is just some random sphere particles filling the volume of a big box.

Water drops on the body of the car are a combination of several techniques. The really tiny ones are just a tillable bump map (a). The small (b) and medium (c) drops were sprayed on, using object paint tool. I decided on spraying them instead of random scattering because that way I had more control allowing me to angle the drops towards the back of the car as if the wind is pushing them. The elongated drops (d,e,f) were placed manually around the body of the car. Then I randomized the look of each long drop using the freeform shift brush. Finally, to conform them to the surface, I used geometry projection script. The drops on the windshield were simplest to make. I just used strips brush to paint a bunch of polystrips and individual polygons, then added a shell modifier and turbo smooth.

With water added all that was left to model were some details like the broken glass of the headlight. I used Fracture Voronoi script to do that. To create the wooden pole, I stamped some wood pattern all over the cylinder in ZBrush and then added a few boxes sculpted into shrapnel and a particle system for tiny debris.

Lighting and materials

I do lighting and materials at the same time, tweaking one or another to get the desired look. I separated the lighting setup in 3 main sections. 1 - the main light (marked green) is a white directional light (you can see its contribution in green frame). 2 - cabin lights (marked red) are 3 point lights. Two are positioned low in front of the characters faking some sort of light on the dashboard, and one is in the back of the cabin to brighten the headliner. Adding to the cabin lighting are two spotlights (marked purple) one for each character face. All the cabin lights are tinted slightly yellow. Since the color palette outside the cabin is in green, blue and gray tones, warmer tones inside the cabin help to bring more focus to the characters. 3 - sidelights (marked blue). There is one big directional light behind the left back corner of the car that provides a bright blue rim right in response to the lightning tearing the sky. A big rectangular Vray light creates nice blue spills of light over the side and the hood of the car. These two lights provide most of the illumination on the right side of the image. The rest of the blue lights are there just to kick up the effect of the two main ones. There is a spotlight to strengthen the rim light effect on the pole, another one for the character faces and a little point light to add more interest to the splashes.

One of my favorite things about V-Ray are the materials. They are so simple to set up and yet so powerful. For example the shader used for the body of the car is composed of four very simple materials using the V-Ray Blend Material. First the base is V-Ray Car Paint Material colored green, next the first coat is a V-Ray material with glossy reflections. This coat is feed through a tillable map of tiny water drops. Same map is also used in bump channel. Having the tiny water drops as a separate material with different reflection properties than the base material makes them more visible and realistic. Next coat (b) is the mud, which is fed through the set of projection maps, one for each of the three axis (xyz) of the car. This is a standard V-Ray material without reflections, just a dark brown color in diffuse slot. It brings nice variation to the car in form of various smudges and specs of dirt. Third coat is a simple chrome material (c) visible through a hand painted map of scratches (for better visibility cropped version shown in the image). Again it is a standard V-Ray material with a scratchy tillable map in reflection and bump slots. All materials in the shader are very simple but together they create a pleasing look. Since so many materials in the scene are reflective it's important to have an interesting environment, in this case an HDR map of a cloudy sky in a V-Ray reflection/refraction environment override slot.

Rendering and compositing

I rendered the image in two separate layers with several render passes. In one layer are the water drops closest to the camera. I rendered them separate of the rest of the image so I could better control their depth of field blurring. In the other layer is everything else. In addition to the beauty pass, I rendered the occlusion pass, z depth, falloff map, and object ID pass (last two for making quick selections in Photoshop).

I started the compositing in Photoshop by adjusting the z depth render pass. I wanted both, the very front of the car and the faces of the characters to be in focus while at the same time, heavy blurring on the back of the car. In 3d space they are at quite different depths, so real, in camera dof, wouldn’t give me the wanted result . Using the object id pass I could quickly select t the right parts of the z depth pass and paint them the right shade of gray, or you could say the right focusing depth. Using lens blur filter with newly adjusted z depth pass I created the dof effect on the beauty pass. After that I adjusted the contrast using curve adjustment layer. On top I added the copy of the beauty pass in screen blending mode, masked through a falloff render pass. This crated nice overblown lights on the car hood and roof that looked right with the lightning in the background. On top of that I added heavily blurred render layer of the closest water drops. After that came the vignette and a discrete lens flare mostly visible as a rainbow ring over the wooden pole. To finish the piece of, I painted in a few loose strands of hair on driver’s head and added few fake bokeh spots. That’s it. Flatten image, save for web and publish.



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