CHRISTMAS DECORATIONS

The accuracy and flexibility of the Turtle make it ideal for Seasonal graphics. Pupils can explore and develop their own programs for drawing images that can be used on Christmas cards, wrapping paper, decorations, murals.....

• Turtle Trees
To draw a simple Christmas Tree the following program could be used:

TO TREE :SIZE PD RT 90 FD 4 * :SIZE LT 117 FD 11 * :SIZE LT 126 FD 11 * :SIZE LT 117 FD 4 * :SIZE RT 90 FD 2 * :SIZE RT 90 FD 2 * :SIZE LT 120 FD 3 * :SIZE LT 60 FD 3 * :SIZE LT 60 FD 3 * :SIZE LT 120 FD 2 * :SIZE RT 90 FD 2 * :SIZE PU END

Once the pupils have drawn the tree they could then change the variables to draw different sized trees. From this they should be able to work out how they could program Turtle to draw more complicated trees.

• How can the tree shapes be used?
Christmas Crowns
Whether producing headdresses for the three wise men or party hats for the end of term party, an exciting and creative activity can be to produce and decorate crowns.

In previous issues of "GO" (issues 1, 3 and 4) we have looked at using variables within Logo procedures. In this party hat activity the hats can be made to different sizes. This involves using the Logo capability to perform arithmetic functions.

TO PARTY HAT :N :SIDE :X FD :X RT 30 REPEAT :N [ FD :SIDE               RT 120               FD :SIDE               LT 120 ] RT 60		FD :SIDE / 2 RT 90 FD :X RT 90 FD :N * :SIDE + :SIDE / 2 RT 90 END

• Program the Turtle to draw patterns on the hat.
The "saw tooth" shape of the hat pattern is based on equilateral triangles, therefore the forward movement = N multiplied by :SIDE. This is required for the return length. However, if the angles were changed in the above procedure, then the user would have to incorporate the use of trignometric functions to calculate the distance moved.

• Stars and shapes
2D symmetrical shapes can be used to produce 3D decorations that can be hung on the Christmas tree or turned into a mobile.

Once the Turtle has drawn the shape it can be cut out and used as a template. There are two alternative methods of fixing the shapes together:

1. Cut out four shapes using different coloured paper and fold them all in half. Glue the back of each half to the back of its neighbour.
2. Cut out two shapes using different coloured paper. Cut a slot from top to middle in one of them and from bottom to middle in the other. Slide the shapes together.

Attach a thread for hanging and decorate with glitter.

• Paper Patterns
Repetitive patterns can be used to draw your own Christmas wrapping paper.

Another Christmas wrapping paper design can be created using STAR, TREE and DIAMOND procedures. Using different values for the variables a variety of sizes can be created. The shapes can then be coloured in.

Snowflake patterns can be created using Logo recursive capabilities. Recursion will be dealt with in later editions of "GO", meanwhile pupils more familiar with Logo programming may like to try to draw their own snowflakes.