Monthly Archives: November 2012

Dissertation fragments: part 4 – Material analysis: Common Material Attributes

In this part I will explain the most used attributes that shaders have one by one. This following attribute groups will be analysed: Common Material Attributes, Specular Shading, Special Effects, Raytrace Options and mental ray.

Common Material Attributes.

Common Material Attributes is where you can control the basic attributes of your shader:

–          Colour: Controls what is the main colour of the object. (Fig1)

–          Transparency: Controls how much transparent is the object. (Fig2)

–          Ambient colour: When there is an ambient light in the scene you can control which colour is seen in the faces that it is lighting. (Fig3)

–          Incandescence: Add colour uniformly to the surface. To create a simplistic bulb effect, you can use the maximum incandescence and it will seem as if the object made light, because it hasn’t shadows. (Fig4)

–          Bump Mapping: Give to the object an optical 3D texture. The object hasn’t true texture but makes the light act on the object as if has. It’s the more simplistic way to represent roughness in textures. (Fig5)

–          Diffuse: Determines the brightness of the material, how much light is reflected from its surface. (Fig6)

–          Translucence: Controls if the material can let the light pass through but being opaque. Translucence tends to be applied to thin objects that are opaque but too slim to absorb all light that pass through. (Fig7)

–          Translucence Depth: Controls how long goes the light trough. On a dense material (like stone) translucence depth will be lower than a material like paper or skin even being the same size.  (Fig8)

–          Translucence focus: Controls the directionally of the scattered light.

RENDERS
–          Fig1: There are three objects with three different colour blinn shaders: Cyan, yellow and magenta.

–          Fig2: In this case, there are three different blinn shaders, with three different levels of transparency.

–          Fig3: Three pink objects with different ambient colour attributes. The complex shape and the cube have a blue ambient colour; the sphere’s ambient colour is red.

–          Fig4: There are three blinn shaders with different incandescence level. On the sphere we can see that has any shadow. It’s because the incandescence is 100% and it is as the sphere produced light.

–          Fig5: In this case, the sphere has a grid texture to reproduce the roughness effect on the surface using a bump map. Tue cube has a browonian texture and the complex shape a wood one.

–          Fig6: In this picture we can see three lambert materials with three different diffuse levels. In the sphere and the cube we can see that ambient light doesn’t work with them. It’s because diffuse level is 0 in the sphere case and very low in the cube. It means that ambient light doesn’t bounces on their surface.

–          Fig7: In this figure there are three equal objects. The only difference between them is the translucence attribute. In the closer one that we can see that light can’t pass through but in the farthest one it can. Respectively they have a 0% and a 100% of translucence.

–          Fig8: There are three equal objects. The only difference between them is the translucence depth attribute. In the closer one light can’t pass through the front face, in the middle shape there is some light that can pass through the front face but only a little can pass through the whole object. In the farthest one all ray light can pass through the entire object.

–          Fig9: In this picture there are three equal objects. Anew the only difference between them is only one parameter: Translucence focus. In the closer shape case all the light rays pass in only one way and they have the power to pass through the object.  In the farthest shape case light rays doesn’t pass in a directional way through the object.

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Dissertation fragments: part 3 – Elements in Maya

Light types in Maya surface:

In the real life there is not only one type of light. This changes depending of the issuer (the sun, a lamp, a reflector…). To be able to simulate all this variety in a digital surface, it were created a different types of light that are equal in all 3D software although they are named in different ways depending on each one. In Maya they have the following names: Point Lights, Spot Lights, Directional lights, Ambient Lights, Area Lights and Volume Lights:

–          Point Light: Simulate punctual light rays to infinite directions in a homogeneous way.  Light bulbs or other little light generator can be simulated using point lights, although in the real world any light generator is 100% omnidirectional. To do this there are some techniques as decide if they should cast shadows or not.

–          Spot Light: They illuminate a cone shaped area. Spot lights are punctual too but the difference between them and Point lights are that Spot don’t illuminate equally in all directions. The artist can limit the influence area and the softness of the light borders in order to create different sizes and transitions between light and shadows. They are the equivalent of the theatre or automobiles lighting.

–          Directional Light: This kind of lighting is not punctual. Once you use it parallel light beams appear in the direction you choose. In this kind of light you can’t control the proximity of the light issuer, only the direction of the light rays manipulating the rotation controller. It’s used to simulate sunshine ambient or to be part of the secondary lighting in a light set.

  • There is a particular direction light no able for Maya Software named Physical Sun and Sky that recreate in a veridical way the Kelvin colour temperature and the different intensities on sun light in lumens during the day. It’s able to reproduce every time of the day only rotating the light controller. If you put it perpendicularly to the ground it will seem to be mid day, but if you put it to 35º to the ground it will seem to be the sunrise.

–          Ambient Light: It’s used to illuminate indirectly the different objects of your scenario. Its function is to illuminate the parts where are not illuminated by direct lighting and they appear too dark. Using the ambient light, illumination seems more realistic and there is no lack of information. But, this kind of light has some big troubles. It’s difficult to obtain a good control of it and it hasn’t a nice quality in shading, so it is criticised by the amount of professionals who have searched some better alternatives.

–          Area Light: These are lights underused because of his large rendering time. They are used to project lights and shadows to simulate the light what pass through a window. It has an excellent shading quality but is used only with still images in info architecture.

–          Volume Light: This kind of light has the advantage that you can know which volume the light influence has, because the only that will be illuminated is all which is inside of the influence sphere. You can configure if you want a punctual or a directional light, and this is another advantage of the light.

Shader types in Maya surface:

There are three types of generic materials: Surface Materials, Displacement Materials and Volumetric Materials. Volumetric ones are used to create atmosphere effects like dust particles, fog or smoke. Displacement ones are used to create deformities in the mesh of an object during the rendering process in order to get wrinkled borders within use too much polygons in its meshes. After that there are surface materials, which give to objects properties to react to the lights and seem to be built with a concrete material. These last materials are the ones that will be mentioned in this dissertation.

Using Maya Render, we realise that we can use the following surface materials: Anisotropic , Blinn, Hair tube Shader, Lambert, Layered Shader, Ocean Shader,  Phong, Phong E, Ramp Shader, Shading Map, Surface Shader and Use Background. Once Mental Ray plug in is activated, 31 new materials appear in the material browser, adding thousands that you can download from internet.

As we see, Mental Ray is a very complete tool than can help us to achieve the material perfection in an easy way, given us dozens of new opportunities.

Mental Ray materials have been developed to be excellent in a very specific material, so they are less versatile than the default basic surface materials. Because that, they will be analyzed in a different way.

Basic surface shaders in Maya:

–          Anisotropic Shader: This material stretch and twist the reflections of the light depending of the relative position of the user. Is used specially to create hair, feathers and satin materials.

–          Blinn Shader: Calculates brightness depending on the surface curvature, the amount of light and the angle of the camera. It reflects brightness and materials of his environment and it’s very accurate. Is used to reproduce metallic surfaces like aluminium.

–          Lambert Shader: It’s a monotone material that produces a soft lighting effect with no brightness. It’s the perfect material to reproduce ceramic or chalk.

–          Phong Shader: It has the same properties than Blinn Material but being more simplistic. It doesn’t reflect brightness or materials of his environment. It’s perfect to reproduce polished bright surfaces ass plastic or porcelain.

–          PhongE Shader: Is the simplistic version of Phong with lower render times.

Advanced shaders in Maya:

–          Layered Shader: Using this material, you can be able to combine different materials to create a complex one.

–          Ocean Shader: It’s used to create simplistic water effects.

–          Ramp Shader: It’s very useful when you want to create materials with different transparency, colour and some other attributes in different parts of itself.

–          Shading Map: Used to get a traditional drawn cartoon effect in a 3D environment. The amount of the Manga based videogames use this material (Naruto, Dragon Ball)

–          Surface Shader: Is used when you want to control transparency, brightness and colour of an object in the time space.

–          Use Background: Apply the background colour to an object.

Some information about characters biography and environment

I’ve been done some changes in names and I wrote  main character’s biographies.

You can download it: Character and environment’s information

Dissertation fragments part 2

I publish this post to carry on publishing fragments of my Dissertation about shading in Maya:

Light types in Maya surface:

In the real life there is not only one type of light. This changes depending of the issuer (the sun, a lamp, a reflector…). To be able to simulate all this variety in a digital surface, it were created a different types of light that are equal in all 3D software although they are named in different ways depending on each one. In Maya they have the following names: Point Lights, Spot Lights, Directional lights, Ambient Lights, Area Lights and Volume Lights:

–          Point Lights: Simulate punctual light rays to infinite directions in a homogeneous way.  Light bulbs or other little light generator can be simulated using point lights, although in the real world any light generator is 100% omnidirectional. To do this there are some techniques as decide if they should cast shadows or not.

–          Spot Lights: They illuminate a cone shaped area. Spot lights are punctual too but the difference between them and Point lights are that Spot don’t illuminate equally in all directions. The artist can limit the influence area and the softness of the light borders in order to create different sizes and transitions between light and shadows. They are the equivalent of the theatre or automobiles lighting.

–          Directional Lights: This kind of lighting is not punctual. Once you use it parallel light beams appear in the direction you choose. In this kind of light you can’t control the proximity of the light issuer, only the direction of the light rays manipulating the rotation controller. It’s used to simulate sunshine ambient or to be part of the secondary lighting in a light set.

  • There is a particular direction light no able for Maya Software named Physical Sun and Sky that recreate in a veridical way the Kelvin colour temperature and the different intensities on sun light in lumens during the day. It’s able to reproduce every time of the day only rotating the light controller. If you put it perpendicularly to the ground it will seem to be mid day, but if you put it to 35º to the ground it will seem to be the sunrise.

–          Ambient Light: It’s used to illuminate indirectly the different objects of your scenario. Its function is to illuminate the parts where are not illuminated by direct lighting and they appear too dark. Using the ambient light, illumination seems more realistic and there is no lack of information. But, this kind of light has some big troubles. It’s difficult to obtain a good control of it and it hasn’t a nice quality in shading, so it is criticised by the amount of professionals who have searched some better alternatives.

–          Area Lights: These are lights underused because of his large rendering time. They are used to project lights and shadows to simulate the light what pass through a window. It has an excellent shading quality but is used only with still images in info architecture.

–          Volume Light: This kind of light has the advantage that you can know which volume the light influence has, because the only that will be illuminated is all which is inside of the influence sphere. You can configure if you want a punctual or a directional light, and this is another advantage of the light.

 

 

 

What is a shader?

A shader is a mathematical model that represents the way that light interacts with the surface of the model.

When a light hits a surface there are three different things that happen: Reflectance, Absorption and Transmission.

Reflectance:  The light hit the surface and then it bounces away. There are different tipes of reflectance depending on the object’s surface.

–          Difuse reflection: If it is rough it produces diffuse reflections. It means that the light hits and its reflections go in so many different directions. As the reflected light goes to all directions, you can see it from any angle equally. The Maya’s material to reproduce diffuse reflection surfaces is Lambert.

–          Specular reflection: Perfectly smooth surface reflects the light in the same angle it arrives. The most common example of how specular reflections work is a mirror. If you change the angle of the mirror you change what you see in its surface

–          There is a middle ground, when the surface is not smooth enough to act like a mirror, where light is reflected in many directions but some portions of that light are reflected in a specular way.  In Maya, to control this middle ground we use as we know as “specular highlight” which helps us controlling what roughness quantity has our material. In Maya, these kinds of surfaces are called Blinn or Phong, which are two different ways to control its roughness.

 

Absorption: Light is converted into heat, it’s not longer visible light and we can’t see it. Different wavelengths acts different in the same surface, some of them are absorbed or not. This is what creates as we know as colours. If a surface absorbs all wavelengths of a light ray, it will be black and it will be easier to heat. If a surface doesn’t absorb any wavelength it will be white. But, if it absorbs every wavelength but green ones, the surface will be green. So colour is the wavelength of a light ray than a surface can’t absorb. This phenomenon is called Specular Colour, because reflections of non-absorbed wavelengths are specular.

 

 

Transmission:  Light goes through the surface. There are some different transmission levels. If light can’t pass through we call this surface opaque and if all light rays can do it we call it transparent. In transmission there is a middle ground too, when part of the light can pass. It’s called translucent or semi transparent surface.

When light pass through a surface his environment changes. The atomic composition of a solid material is different than air, so light rays tend to change their direction. It’s called refraction. Depending on the difference between the normal direction and the one through the solid material it will have a different refraction index.

Depending on the qualities of the surface, different light spectres will interact in a different way whit it, and only combining these mathematical models we can do all the material variations we need.

 

 

I want to add, that I choose the 5000-word option to defend my thesis.

Dissertation fragments part 1

This post is created to publish a part of my Dissertation about shading in Maya:

 

What is rendering?

Render in the informatics slang is a word that define the process of generate an image from a polygonal model. Rendering is used to simulate 3D spaces in a plausible way, calculating the light behaviour or the lack of it on different shapes, materials, textures and ambient. To do that, it’s needed a render motor.

What is a render motor?

A render motor is a plug in implemented in 3D software that is used to calculate in a realistic way the light incidence on a model created virtually.

Before starting the analysis of the different types of lights and materials, we should do a little revision to the different render motors existing in Maya. The more extended and known are: Maya Software, Mental Ray, V Ray and Maxwell Render.

–          Maya software: Is the default render motor in Maya. It was developed by Autodesk and it is the more basic one, because it doesn’t calculate the indirect light incidence. It is the faster render motor but the one that create the poorest results.  However good results can be achieved with a large learning process in lighting in order to create complex light sets with different light issuers for bounced and direct light.

–          Mental Ray: It’s a render motor developed by Nvidia that has been turning one of the most used ones. It is very powerful calculating bounced lights of the scene and it has an accurate capacity to reproduce reflections and refractions. Although its results are not perfect, they are very similar as the real world.

–          V Ray: It’s a render motor developed by Perchaos Group and is the direct rival of Mental Ray, and the one that has more similitude with it. The public opinion is divided in which is better, but it seems that V Ray is faster than Mental Ray and this makes it a little better.

–          Maxwell Render: Developed by Next Limit Technologies (owners of Real Flow) is thought to be the next render motor generation. Defined as a physic render motor, Maxwell Render calculates images basing his actions in real physic laws and getting perfect light simulations. It makes Maxwell Render perfect by render perfect photorealistic images but with a large render time.

Once defined the different render motors, it has to be specify that not all materials works in all motors. In Maya, the most basic ones can be rendered using all the render motors (getting different results depending of the one selected) in other hand, there are materials optimized only for one render motor.

In this work, I will explain the most common materials in Maya Software and Mental Ray, that are the most used.

 

 

Final Front-side views finished

In this post you can download the last version of the simplistic Front-Side views of the two main characters.

Preproduction is almost finnished, and I will publish the rest of documents soon.

 

Download Front-side Cuppy views

Download Front-Side Toashan views