MATERIALS Chakrit Watcharopas Reference: The Essential Blender: The Official Guide to 3D Creation with the Blender Open Source Suite   Author Roland Hess Publisher No Starch Press Publication Date 2007-09-27

Managing Materials Materials are created and linked to objects in the Links and Pipeline tab of the Material Buttons (F5) The Material buttons will display the material for the active object in the 3D view Once a material is linked to an object, it is quite simple to change or remove that link Changing material is just a matter of choosing a different material from the drop down menu

Components of a Material Blender materials each have four main components: base color shaders reflection and transparency textures (will be mentioned in the next class)

Base Color Under Material buttons, "Col" sets the overall color "Spe" sets the base colors for Specular "Mir" sets the base colors for Reflections

Shaders Diffuse shading explains the way that renderer calculates the general shading of the object Lambert: Blender's default shading option Lambert is a good shading model for plastics and other glossy, fairly smooth substances

Shaders (2) Minnaert shader can affect the way that light plays on the portions of your geometry that face the camera directly, as well as the portions that are perpendicular to it Minnaert is useful for cloths, e.g., velvet, and can also be used for giving backlight effect

Shaders (3) Oren-Nayer is a shading for matte surfaces Try using Oren-Nayer, unless you are working with cloth, plastic, etc Although Oren-Nayer doesn't generate any texturing based on the "Roughness" value, it simulates the more diffuse scattering As such, Oren-Nayer works well as a basis for human skin materials

Shaders (4) Toon shading breaks the shading into three flat regions - shadow, mid-tone and highlight Toon allows you to control the sharpness of boundaries between them Using correctly in combination with Toon specular shader and edge rendering option, can produce an effect much like the standard three-part shading of hand- drawn animation

Shaders (5) Although Diffuse has slightly different controls, it also has a Ref (Reflectance) value Ref represents amount of light that reflects from the surface and reaches the camera A Ref value of 0.8 means that 80% of the light that reaches the surface from lamps is used for shading purposes For most cases, Ref with 0.8 is a good starting point

Shaders (6) The lower set of controls is for materials that have Specular highlights Specular highlighting is a way of faking the reflectance of light on a surface Many times real world materials will appear more believable if Spec value is 0 or near it

Shaders (7) Spec value indicates intensity of the highlight Metallic objects should have highlight colors (Spe color from the Material tab) near to their base color Hard value controls the size of the highlight "Harder" substances like glass or diamond exhibit tiny, tight highlights, while softer substances (like cloth) have a larger highlight

Shaders (8) Blinn specular shader pairs well with Oren-Nayer diffuse shader for most matte and naturally occurring surfaces Phong works well for glossy plastics Phong and CookTorr can produce good results for shiny metallics

Reflection and Transparency Reflectance in Shaders tab is different from Reflectance in Mirror Transp tab Reflectance in Mirror Transp tab refers to actual visible reflections, ones seen on a mirror

Reflection and Transparency (2) We can simply create reflective surfaces in Blender by enabling "Ray Mirror" option in the Mirror Transp tab Adjust RayMir between 0 (no reflection) and 1 (full reflection) Above method uses Blender's Raytracer Raytracer follows light rays from the camera back to their source It creates great effects, but can be costly in terms of render time

Reflection and Transparency (3) In order for "Ray Mirror" to work, make sure that the "Ray" option is turned on in the Scene buttons (F10) If you want your reflective objects to have an overall color cast (like the tinted reflection in red and green Christmas balls), you will need to set the "Mir" (Mirror) color in the Material tab

Reflection and Transparency (4) Alpha in CG terms tells how much light passes through a surface Alpha scale runs from 0 (fully transparent) to 1 (completely opaque)

Reflection and Transparency (5) Changes to the Alpha slider, labeled "A", will be reflected immediately in Material preview To visualize Alpha effect in the 3D view, select the object, switch to the Object buttons (F7) and enable the "Transp" button on the Draw tab

Reflection and Transparency (6) There are two ways for Blender to render Alpha If you don't need to simulate refraction, the best way to do is to use zTransparency If you need refractive realism, you will need to use raytraced transparency

Reflection and Transparency (7) To use zTransparency, enable the "ZTransp" button on the Links and Pipeline tab of the Material Buttons To use raytraced transparency, make sure that zTransp is disabled in the Material tab, then enable "RayTransp" in the MirrorTransp tab IOR slider just below the RayTransp button controls the Index of Refraction Find the value of Indices of Refraction for glass, water, sapphire and diamond

Reflection and Transparency (8) Two objects rendered with Ztransp (left) and with Ray Transp (right)