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Occlusion pass guide

About tutorial

In this tutorial I will try to cover everything you need to know about occlusion pass in 3 simplified parts. The first part is explains what an occlusion pass is and what its good for. The second part is all the technical info on how to make an occlusion pass. the third part explains how to use it.

WHat is occlusion?

To simplify the explanation, just think of a situation when all your objects have a simple white color and your scene is lit equally from all directions by a white light. Basically this should result in a blank white image, but what happens when some objects block a certain amount of rays that should have gotten to other objects ? those rays don’t reach the other object and as a result, the parts where the rays were blocked will become darker. The more rays blocked, the darker the surface will be. So basically what we get is a white image with dark areas where geometry intersects with itself.

WHy using it?

The resulting occlusion pass gives very accurate and smooth shadows that resemble the result of global illumination. Compositing these shadows over your final render can significantly improve your image in many ways,it can mainly improve your shadows, give more depth to your scene and really helps to better show all the details of your models.

Wherecan I make it?

In any major 3d package that has mental ray (or other rendering engines that support it) basically.

WHen to use it?

After you decide you are finished with your scene and have rendered your image.

How

There are two simple ways to get an occlusion pass. Both ways will usually give a similar result, the AO shader method can often be faster and gives much more control but the shader is not included by default in the early versions of some packages. experiment with both so you could decide which works best for you.

Click here to view large image

Note that these steps are demonstrated with max but they are similar in every major 3d package that has mental ray.

Skylight method
1. Save your scene as a new file to avoid losing any data.
2. Set your renderer to mental ray.
3. Set the background color to white and the global light to 1.0 (software’s default ).
4. Select all the objects and give them a standard material, set it’s color to white.
5.In the rendering options, turn final gather on (more samples for higher quality).
6. delete all the lights in your scene and add a sky light, set it’s color to white.
7. render.

tip – instead of using a white diffuse color, you can also use the AO shader in the diffuse color slot for more fine tuning.

Ambient occlusion shader method
1. Save your scene as a new file to avoid losing any data.
2. Set your renderer to mental ray.
3. Set the background color to white and the global light to zero (everything is black).
4. select all the objects and give them a standard material, set it’s color to white.
5. place an ambient/occlusion map in the self-ilumination slot (more samples for higher quality).
6. delete all the lights in your scene (they are unnecessary for this)
7. render.

quick info on the shader parameters:
samples – depending on the quality you want and the time you have, 128 is usually enough to get and high quality result.

Dark / bright – its usually best just to leave it as is.

Spread – Higher values soften the shadows between the geometry by expanding them further.

Max distance – when set on 0 it works like the skylight, any other value makes it calculate the occlusion “locally”. this parameter determines the distance of the local calculation. this is a must for indoor scenes.

Optional tips for improvement

Bump maps - If you wanna go extra with the occlusion pass, you can include the bump mapping of your objects to emphasize it more. Just make a copy of the material and put back the bump map in it’s slot for each object.

Adding / hiding geometry - sometimes you might wanna try adding some geometry outside the frame just so it would cast more shadows in desired areas. In other cases, some important areas get too shadowed because of certain geometry blocking too much of the light to it. It might help sometimes to exclude, hide or delete part of the geometry when making an occlusion pass.

Rendering more than one pass – this goes mainly for large scenes, you might wanna get different occlusion passes with different settings and different geometry (as mentioned above) so you could later on decide which pass works best with each local detail.

Applying it on the final image / sequence

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In this example I chose to start with a quick light setup for the first render which is quite flat and with very little contrast because I knew I’m going to go massive with the editing. Take your render and your occlusion pass(es) to Photoshop and get to work.

The quick way to use the occlusion pass would be to slap it over the render, change the blending mode to overlay or multiply and adjust the layer’s opacity to the point it doesn’t get burned. But if you want to make the most of the details of your geometry, this can be taken one step further. the main idea behind it is to use it with as many different situations as you can think of (different occlusion settings, different blending modes, adjusting different colors and contrast and so on) and create masks to keep only the parts that improved on each layer. In this example I really took the occlusion usage to the extreme just for the demonstration (usually I don’t get more than a couple of quick layers). One thing you should always keep in mind is not to over do it, applying the occlusion passes quickly raises the contrast level of your image so make sure you don’t get stuff burned too much.

More examples:

Click here to view large image

Click here to view large image

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Making of Bad Dream


First of all I want you to know that this image was created for a competition, the goal of which was Lighting & Rendering Atmosphere.

As this is a making of article, I’m not gonna cover every step of the whole process. I assume you have some basic knowledge of 3D in general, and basic to intermediate level for all the 3ds max users.

First I created my concept sketch to focusing better on my idea for the challenge. I wanted to play most with the lightening and atmosphere so i concentrated more on that. The baby in the scene was used to give more expression to the whole situation.


For me it’s better to start modelling from simple shapes, using the box modelling technique. So I started modelling the head from a simple box. It’s better to study your model first and find how many divisions the box needs to get the look of the face better and faster. That’s why I recommend to always start with the simplest shape, and adding details gradually.

stage 1

stage 2

stage 3

stage 4
A very important fact to consider is the modeling flow. I’m talking about the way you build the surface; edge loops/edge rings.

Ok, after dividing the box several times, I converted it to a editable poly, and started adding details. Although I was dealing with a complex organic modeling, the tools I’ve used were very few. 3ds max has a very robust polygon toolset. 90-95% of the work was done using 2 or 3 tools.( cut, extrude, bevel, weld). Cutting here and there, I’ve modeled the face of my character. I built the mask using surface patch technique. Drawing splines first, and than adding the surface modifier.

stage 5

stage 6

stage 7

stage 8

stage 9

stage 10

Using the method above, I started modelling the body. Starting from a simple shape/ turning to poly/ and adding detail with the tools I’ve mentioned before.

Now that I’ve finished the modeling, it’s time to skin it. Doing this I can make the pose, like my concept drawing.
I built a fairly simple skeleton rig with max’s standard bones and added some simple controls for the limbs.
I added the skin modifier on top of my poly surface first, and then all the bones of the skeleton rig.


As soon as the skin phase is finished, it’s time to do some texturing work!… I added Unwrap UVW modifier and started pulling and pushing the UV’s, trying to make them as flat as possible. It’s good way to be in sub object mode, so you can see directly in the view port, all the polygons you select in the UV editor.


After I opened photo shop, I imported a screen shot of the UV’s, and started painting the diffuse map. I wanted the skin to be smooth and translucent, so I don’t need to create a bump map for the skin.

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Making of Mama


I’m going to explain to you how I created my latest personal artwork called “Mama”. I did it for the 50th birthday of my mum, which was several weeks ago. Obviously all the things I did can be done in many different ways. The techniques that i have used in this occasion were chosen depending on the circumstances such as the timeline.

Well I’m going to begin telling you I used 3dsmax8, Zbrush and Photoshop, and was rendered using 3dsmax’s Mental Ray. Why? Because it has an easy and fast Sub-surface Scattering simulation, which as you probably know also includes a variation that lets you make realistic skin called “SSS Fast Skin”.

Modelling:
The head is probably the thing that took the most time to model, although Zbrush, apart from making the job better, it makes it faster. The point was giving the model her characteristic charm, which unfortunately you don’t know. The model has 6 subdivisions, apart from the base mesh. To speed up rendering, I just exported the 3rd subdivision (Level 4) inside max, and the rest of the detail worked damn good with a normal map!



The eyebrow was modeled separately


0 = Base model geometry. It’s completely flat.

1 = I apply the shell modifier to add depth

2 = Symmetry to X axis

3 = Symmetry to Y Axis

4 = Planar UVW Map

5 = FFD Box modifier of 8x8x2 points (FFDBox=lattice in maya)

6 = I deform the cage of the FFD Box until adapting it perfectly to the shape of the sofa (the sofa

is kinda deformed by the weight of her body, so it’s not like bending it)

7 = Turbosmooth modifier, 2 iterations

8 = Noise, small size

9 = Noise, big size

10 = Displacement set with a fabric image & Final look. (It’s Difficult to see the diferent with

this image size though)

The book process was quite simple. I just did 2 kinds of Sheets.

First of all, we have the “Sheet group” which is a piece of geometry to simulate the pages that, due to whatever reason, stay together when you open a book. I just added a simple displacement map aligned across the width of the geometry. The key in making it believable was changing the width in each block, so it looked more random. Changing the shape of each group was also useful. I used FFDBox 4x4x2 for that.

Secondly I did the individual sheets, which were placed mostly in the center of the middle opening, where she’s supposed to have the thumb finger. I also used FFDBox for giving each one the appropriate shape.

Notice in the image that each kind of sheet has a slightly different color, so you get an idea.


Illumination:
The lighting is pretty basic. I tried to simulate the lighting of my living room. I started not using GI or final gather, just to make quicker renders. Then the setup began to work quite good and I ended up using it, so no GI.

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Making of the Incredible Hulk

MODELING
Making realistic character even fantasy character is not an easy task so the step by step tutorial is almost to impossible to write. But making of article can be very useful as the example of different tasks that has to be done in order to complete such project.
In this making of I will show you one of common workflow used in game and movie industry.
First thing to do is gathering reference images an studying the character, more you get your self familiar with the subject you are modeling more successfully final model will be.
Next thing to do is building solid base mesh.
There is many techniques for building base mesh but I found that most easy and artistic way is to sculpt hi rez mesh and than retopologize it. For this task i use Zbrush.
Next image show retopologised mesh that can be used later for many projects.




After building base mesh it is time for hi rez sculpting, that is where the real fun start.
Using Zbrush standard tools in the few hours a have build hi rez sculpt containing over 12 million polygons.
Most important advice I can give for sculpting is to stay patient and not to rush with dividing your model to soon but focus on the overall form of sculpture, wrinkles and pores are last thing to do.

TEXTURING
After completing hi rez mesh I have exported model as obj file at lowest division level for generating uw maps. I often use Headus UWLayout for this job because is gives me more results in less time.
After generating UW’s model is ready for generating normal maps (1) that is important for transfer hi rez details to lo rez mesh. I also use normal map as template for other maps.
Zbrush also can generate cavity maps (2) that makes some kind of fake occlusion map useful for shading some parts of the model.
Details extracted from cavity map can be used for making spectacular map(4).
I render my maps at 4k resolution so it can hold al details necessary for skin pores and wrinkles.

Using generated maps as template I have painted color map also (3).

RENDERING
For rendering I like to use Mental Ray because of great SSS shader possibilities.
I just load up maps to appropriate slots in fast skin shader that already comes quite tuned.

Besides that I have rendered few more passes like extra spectacular/reflection and ambient occlusion so I could have more control over this things later.
When it comes to lighting i like to keep it simple. In this example i use four lights setup, two back light slightly blue and two front lights also colored but with warmish yellow.

With this kind of setup image was rendered in 5 to 6 minutes at 3000 px in height.
Last step is to compose all renders using Photoshop.
I hope you will find this tutorial useful and feel free to contact me for any farther explanations.

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Making of Odin’s Final Battle

Software Used: 3ds Max, ZBrush, & Photoshop

Hi everyone, I would like to share with you a short step-by-step process of my latest artwork, Odin’s Final Battle. I created this image for a competition with a steam punk mythology theme. After I decided to join the competition, I was soon doing research for a good story, and I chose to go for the Nordic myth, Ragnarök. Odin was one of the main characters in this story, and because we have to put a steam punk touch in our images, my idea was to make a human version of him, but with a metal suit of armour powered by steam.

The first process was the modelling. I usually start with the head, so I gathered some references for his face. Odin is the ‘father of the Gods’, so I had to make his face a little older and wiser than an average guy would look. After I create a base mesh in 3d Studio Max, I imported it and then began to sculpt the face in ZBrush (Fig.01).

Fig.01

The next process was to export the subdivision 2 model and create a normal map from the high poly head. In order to do this, I used XNormal, which is a very good freeware for baking normal maps. I place the subdivision 2 model in the low poly slot and the highest subdivision in the high poly slot, and then chose normal maps as an output and hit render. Here’s the head model with the baked normal maps (Fig.02).

Fig.02

After the head model was done, I decided to texture it right away. I used ZBrush and Photoshop for this process. ZBrush was mainly used to make the base texture, while Photoshop was used to create the more detailed texture of the head. I also decided to use Mental Ray for the rendering because of its powerful SSS shader. For the hair and beard, I used extruded planes. The hair was then painted over in Photoshop later on, but it was important to have a good overall feel for the face so I had to at least make descent looking hair at this stage despite going to paint over it later. Here’s a test render for the head, also with the SSS settings (Fig.03).

Fig.03

The next step was creating the armour and the rest of his body. For the upper armour I used a concept made by my team mate. The modelling was done in a similar way to the face, by extruding planes. Creating a good texture was again also crucial in this process. I wanted to make his armour look weathered and battle damaged, so I mixed a few images I found on CGTextures.com and on top on that I applied a little paintover and some colour adjustments. This is the early test of his armour with the texture and shader settings (Fig.04).

Fig.04

After I completed the upper armour I continued to make his lower body. The steps were still the same here: creating the base mesh, sculpting in ZBrush, baking the normal maps, and then creating the texture and shader. After his full body was complete, I tried to render it and here’s the result (Fig.05).

Fig.05

I wanted to create not just a single character, but a complete scene. So I began at this stage to make the environment. The idea was to put Odin standing in front of his throne, ready for the last battle. I made the throne first, and then added a touch of steam punk and skulls (because he is the God of death). I also added some gears and pipes to complete the environment (Fig.06 – 07).

Fig.06

Fig.07

I used Mental Ray as the rendering engine. To light the scene I used just one skylight and 5 other Max standard lights (4 omni and 1 target spot light). You can see my settings in Fig.08.

Fig.08

I usually keep my render settings simple, so for this scene I only enabled Final Gather in the indirect illumination tab. I also used HDRI maps for extra light in the scene. Once happy, I simply hit render … But then a problem occurred: I didn’t have enough memory to render the whole scene. To be able to do this I had to decrease the size of the textures using bitmap proxy. Usually reducing the texture size is not a good option if you have close-up shots, but for this scene, since the camera wasn’t going to be too close to the character, the textures would still hold up for the render (Fig.09).

Fig.09

The whole scene was rendered in 3 passes, which was the raw render, the ambient occlusion pass, and the ZDepth pass (Fig.10).

Fig.10

I composited the passes in Photoshop, and also re-painted the hair and added some more details and effects. Here is my final image of Odin in his throne room (Fig.11a – d).

Fig.11a

Fig.11b

Fig.11c

Fig.11d

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