If an IOR of 1 is used, then light reflects/passes off/through the surface without changing direction, meaning it has the same density as air. Compound materials such as wood, stone, concrete etc.But if you need a value then below is a good starting point for the most common materials. The truth is there is no actual value, it depends purely on the material and its characteristics such as dirt, scratches rust and so on. You can find many IOR tables on the internet and they all give different values for real world materials. A formula known as Snell’s law is used to describe the relationship between the angles of incidence (Viewing angle) and refraction which gives you the IOR. This is why by default it is locked to the refraction IOR. Therefore the same IOR value is a good approximation for both reflection and refraction. IOR can also be used to measure reflection and how light reflects off a surface relative to the viewing angle (Yourself) and although calculated in a slightly different way they are usually directly proportional. Place a stick in a pool of water, notice how the stick bends below the water surface? As light passes through the water surface it changes speed and bends. IOR stands for index of refraction and is used to measure how light refracts through a surface relative to the viewing angle (Yourself), confusing at first but read on. Fresnel studied the behaviour of light and how it was transmitted and spread by different objects. The Fresnel Effect was first documented by the French physicist Augustin-Jean Fresnel (1788-1827). Fresnel is a good approximation and is as close to physically correct materials as you can get whilst keeping the rendering times low. If you position yourself to the side of the monitor and look into the glass you will clearly see a reflection of the environment, but if you position yourself directly in front you will notice that the reflection is reduced. A good example of this would be to look at an old CRT monitor, where the viewing panel is glass. Most materials except metals have a Fresnel reflection, making the reflection strong at glancing angles but weak at more front on angles. White reflects the entire visible colour spectrum whereas black absorbs all colour. Polished marble (Depending on colour), 30 - 70 %ĭiffuse colour also affects the reflection intensity.However the following can be used as a guide.īy default the reflection colour acts as a filter for the diffuse colour and the stronger the reflection colour the dimmer the diffuse colour. You would commonly use a grey scale value to determine the reflection strength and there is no right or wrong value so you will have to take your best judgement. By using colour instead of grey scale you will get coloured reflections. White RGB (255,255,255) is fully reflective and black RGB (0,0,0) is not reflective at all. Like diffuse it uses a colour value to determine the reflection strength. The light rays are bouncing all over the place, and not being absorbed.Ĭan be used to simulate dust on a surface by controlling the way the surface reflects direct light. If you render an object that is pure white or pure black you will notice that there is no contrast. When creating a white or black material, set the colour values to an off white RGB (245,245,245) / black RGB (2,2,2). It is important to understand that no material in the real world is pure white RGB (25,255,255) nor pure black RGB (0,0,0). This is the actual colour of the surface, reflection and refraction colours can affect the visual appearance of this colour. A more in depth look at each setting within a Vray material for version Vray 2.0.
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