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 Turtle 1.0 - Turtle Graphics in any SVGA BGI Mode   Patrick L.Pollet 14.12.1992

This TP5.5+ unit allows to re-use the Turtle graphics calls in any graphic mode supported by a BGI driver. This unit exports all turtle graphics calls present in TurboPascal V3.0 and in compatibility unit Graph3 provided with subsequent versions. The HiRes and Graphmode calls are not supported and were replaced by more general calls (GraphOn,GraphOff) to accept all standard graphic modes and drivers.


TURTLE version 1.1e Unit that allows turtle graphics in any BGI mode Copyright (c) P.Pollet 1991,1992 Portions of SVGA handling copyright (c) 1992 J.P.Hardgrave Procedures and Functions names (c) Borland Int'l 1987-1992 This unit is hereby donated to the public domain provided: - the copyright notices are not removed nor modidied. - proper citation of authors is made upon usage in other packages - the archive contents is not modified Please report all problems, bugs, suggested modifications to the author Dr Patrick L.Pollet ppollet@cismibm.univ-lyon1.fr Institut National des Sciences AppliquВes Centre informatique du 1er Cycle Bat 110 20 avenue A.Einstein 69621 Villeurbanne Cedex France Archive contents: TURTLE DOC This file DRAGRECT PAS 2411 14.12.92 10:17Demo program Clover dragon FOREST PAS 3737 14.12.92 10:44Demo program draw a nice forest NICETREE PAS 3124 14.12.92 10:45Demo program Draw a nice tree SVGA INI 3192 14.12.92 10:31Include file to use SVGA.BGI SVGAREG DOC 3122 14.12.92 10:27Registration form for SVGA.BGI SVGA256 BGI 6335 09.09.92 9:11SVGA.BGI driver (C) J.Hardgrave TREEREC PAS 1539 14.12.92 9:55Demo program Regular trees TURTLE PAS 24153 14.12.92 10:30Source code unit Turtle TURTLEDM PAS 4576 14.12.92 10:05Demo program Play with turtle VONKOCH PAS 1977 14.12.92 10:29Demo program Von Koch SnowFlake Why did I wrote that unit ? Do you remember that little turtle with a pen at the tail that was the main feature of the Logo language ? A toy to learn computers to kids ??? Well not so... For my fellow teachers in C.S., turtle graphics are an exellent introduction to recursion , with quite attractive visual effects. Drawing "dragon curves " (Von Koch snowflake, Peano's curves...) is so natural with this little friendly animal.... Another application is in the representation of 2D shapes by relative motions of the turtle ; that by a couple ( distance, angle ) from a previous point. This makes the manipulation of the shape much easier than with the standard cartesian coordinates representation. A translation just requires changing the starting point of the drawing ; rotations can be obtained by changing the turtle heading and zooming is done by changing the pixel/distance ratio for the turtle motions. Nearly no trigonometric calculations are required to transform a shape ... Borland had introduced turtle graphics with TurboPascal 3. In the subsequent versions, a compatibilt unit, TURBO3 was provided but, even with version 6, it can only do turtle graphics in the old CGA graphic modes !!! Quite desappointing at the era of SVGA boards.... This unit , TURTLE.PAS make possible the use of a turtle with any graphic mode supported by the Graph unit. whether it is a standard graphic mode (EGAVGA,HERC,IBM8570..) or a user written BGI driver such at the remarkable shareware SVGA drivers written by ....... To allow a nearly direct recompilation of previous programs, the entries points are identical , in names and parameters with the Turbo3 unit interface. technical notes: This unit has been tested with all BGI drivers supplied by Borland Int'l in Turbopascal packages version 5.5 and 6. User installed BGI drivers were tested only with SVGA.BGI driver of J.P.Hardgrave. The source code is self-documented.