This is an old revision of the document!
Real space: Surfaces in space
In addition to space curves, CGRAPH can also display surfaces in three-dimensional space where the x, y and z coordinates are functions of two variables. With this definition, any surfaces or closed objects can be drawn in three-dimensional space.
For surfaces in space, the availability of variable names in the function editor is limited to x and y. Enter the desired function in the input field for the function, or select one of the existing functions by clicking on the arrow to the right of the input field.
If the function is only available as an implicit equation of the form f(x,y,z) = 0, the graphic type Implicit surfaces can be used instead.
If the checkbox Only display a surface… is activated, CGRAPH hides the input options for the function for the x and y coordinates and replaces them with x and y. A surface above the x-y plane is then displayed.
CGRAPH displays surfaces in space within the ranges specified for the variable.
After clicking the Create graphic button, CGRAPH switches to the Display tab and displays the graphic.
The default values can be viewed in the tree on the left-hand side. Clicking on the (optional) parameter also activates the parameter's adjustability at the bottom. An explanation of this function can be found in the notes on changing the parameter in the graphic display.
Double-clicking on the text next to the coloured symbol allows you to set the colour and appearance of the graph. Clicking on the coloured symbol itself hides or shows the graph.
The ‘surface’ shown here is a complete sphere in space. The default values can be changed later – clicking on one of the values switches CGRAPH back to the tab with the default values. The graphic is adjusted as soon as the Create graphic button is clicked.