This colour picker is a VRML prototype node (PROTO) based on the HSV colour space model, commonly known as the colour wheel. Those interested to learn more about colour perception and its description may read the excellent article about Colour in Wikipedia.

This implementation ColourWheel.wrl maps the saturation (S) and value (V) on a square instead of a triangle, therefore the maximal saturation with maximal value (brightness) is located at the upper right corner, black (V=0) is along the left vertical side and the transition from black to white goes along the bottom side.

Outside of the hue (H) wheel you find on the upper side two corner triangles:

• the right corner always displays the selected hue at full saturation
• the left corner displays the colour resulting from the S,V values selected on the square. A click on this corner will log on the VRML console the color coded as RGB triple, ready to be pasted into VRML node.

Below the hue wheel you will notice a rotating cube and a rotating cylinder; they are shaded with the selected colour as displayed in the upper left corner. Their purpose is to show the combined result of the standard VRML illumination model and moderate motion. Colour of moving objects are not perceived the same way as of immobile ones. A click on this objects will toggle them between mobile and immobile state.

By clicking on the image you can start a test example ( test_colourWheel.wrl) provided you have installed a VRML renderer in your browser. The example has been tested with the Cortona VRML Client. Whenever you change hue or the saturation-value pair an event sends the new colour to the object presented on the left side pane.

Louis JEAN-RICHARD

November 2004