COLOUR MATHS: INCREASING TEXTURE RANGE

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COLOUR MATHS: INCREASING TEXTURE RANGE

Colour maths can be used to increase the range of colours produced from a texture. In this example we will be using the texture on a simple object, but the same principle could be applied to image based lighting. The reason this works is that the Poser material room allows us to use colours brighter than white and darker than black to create our pictures. Of course in the final picture we can only see the normal colours, but once all of the steps required to calculate the final image have been taken into account, black and white in a picture will normally come out as shades of gray.


Fig 1: Normal Texture  

Figure one shows the results of using an unmodified photo as our texture. The picture comes out looking rather dull and washed out.


Fig 2: Enhanced texture  

Figure two shows us the result of using some simple colour maths to increase the range of colours we are getting from our texture. The whole picture is much clearer, the whites whiter and the blacks blacker. More detail is visible in the final picture. Figure three shows the shader node tree used to create this effect.


Fig 3: Node setup  

This shader tree needs two color maths nodes and a user defined colour. The first step is to increase the range of colours in the picture. We do this by plugging the picture into value 1 of a Color_Maths Multiply node, then plugging a User_Defined colour into Value2. We set all three values here to 2, to double the range of colours in our texture.

At the moment, the textures run from 0% to 200%. This would produce a very bright final texture, so we are going to subtract 50% from the output. In order to do that, we have plugged the output of the multiply into Value_1 of a Subtract color_math node. This time, we are using the colour of Value_2 to produce our effect. This colour has been set to a mid gray - the equivalent of 50%. This produces a final result that ranges from -50% (Blacker than black) up to 150% (whiter than white). When this is run through Poser's rendering engine, the extremes will be taken into account, producing our wider range of colours.

This effect can be used to with image based lighting to increase the range of lighting producing by a simple picture, on normal textures to increase their impact, or even on the output from other nodes.