Drawing Circles And Curves; Updating The Graphics Area - Tektronix 4106 Operator's Manual

GETIING ACQUAINTED
DRAWING CIRCLES AND CURVES
You can draw simple curves by first specifying the graphics position with the MOVE
command, then using the CURVE command with a series of xy-coordinate points .
Watch how the curve is drawn after you enter the CURVE command .
MOVE 1000 , 1000
CURVE ARC , 1600, 1600,2200 , 1000,2800 ,400 ,3400 , 1000
The MOVE command specified the graphics position . The CURVE command first
specified that the type of curve to be drawn is an arc , then defined a series of four
xy-coordinates through which the curve was drawn.
You can also create full circles using the CURVE command. In this next
demonstration , you will create a circle as a panel and fill it with a pattern . This time ,
the panel will not be part of a segment .
Begin by entering the following command sequence (without first
entering an SGOPEN command) :
FILLPATTERN 15
BEGINPANEL 400 ,2600 , 1
CURVE ARC , 1400,2600 ,400 ,2600
ENDPANEL
The first two values following BEGINPANEL define the graphics position
(400, 2600). The third parameter (1) specifies that a border be drawn .
The next four values represent two xy-coordinates that the terminal draws through ,
starting from the graphics position :
• The first two values
(1400, 2600)
specify the first point to draw through - the
distance between this first point and the graphics position defines the circle 's
diameter.
• The next two values (400,2600) specify the same point you specified in the
BEGIN PANEL command - so a circle is drawn.
Since you did not open a segment, this circle is not part of a segment definition.
You can draw other types of curves , which are described in the
41061410714109/CX
Programmers Reference Guide.
UPDATING THE GRAPHICS AREA
Remember that segments are retained in memory. Watch what happens to the
curve and circle you just drew when you erase (or, update) the graphics area.
Locate the GEras key (the shifted version of the Dialog key) at the
left end of the top row of keys . Now, watch the screen and
press GEras (remember to hold down the Shift key) .
The entire display is momentarily erased ; then Segments 1 and 2 (the blue panel ,
star, and bricks) are redrawn . Graphics that are not part of a segment (the circle in
this case) are lost , while the graphics that are defined as segments are retained .
2-14
4106/4107/4109 OPERATORS