Sieve V1.0 (c) 1991 Richard Kelly BACKGROUND The idea for this program came from the Scientific American but I don't remember which issue that was. It generates pictures using simple rules. The program allows you to change the colour palette easily. It has several inbuilt palettes and you can easily modify the one that is displayed to produce smooth or striped palettes. The pictures that the program generates look quite different with different palettes so its worth experimenting with the various options in the "Colours Menu". THE PICTURE RULES The basic idea is to colour each x,y point depending upon the value of some 2 variable function F(x,y). The colour index number is the remainder of F(x,y) when divided by the maximum number of colours. In other words Colour index of point (x,y) = F(x,y) MOD number_of_colours The resulting pictures can be very surprising. It is reasonable to expect contours of colours giving banding effects. You see this for some formulae but the formula 2 2 gives some very interesting patterns. X + Y The program has several inbuilt formulae (see the "Formulae" Menu). There is a scaling factor used in generating the pictures. The scaling factor is used to translate the screen co-ordinates to the x,y values used in the function. The co-ordinates of the point (x,y) within the picture box are multiplied by the scaling factor before being used in the formula. With different values of the scaling factor You can get some quite different pictures for the same formulae. USING THE PROGRAM When the program is loaded you will recognise the following different areas in the display:- a) A 10 item menu at the top right b) 3 slider bars just under the menu c) A palette strip along the middle d) 3 picture boxes at the bottom One picture box has a thick frame - this is the currently selected box. Operations which effect a picture box will operate on the current box. Initially the picture boxes are empty and each has a two line header above it. This shows the formula that will next be used for the picture and the scaling factor that will be applied in generating the picture from the formula. Using Menus Selection from the menu options can be made by clicking the mouse (either button) or by the Amiga keyboard function keys as shown below. ________________________________________________________ | | | | | | | F1 | F2 | F3 | F4 | F5 | |__________|__________|__________|__________|__________| | | | | | | | F6 | F7 | F8 | F9 | F10 | |__________|__________|__________|__________|__________| There are four different menus:- The "Main" menu, the "Formulae" menu, the "Colours" menu and the "Palettes" menu. Each menu has selections which will take you to another menu; for example F10 in all except the "Main" menu will take you back to the main menu. There is a shortcut method to get at each menu selection without heving to navigate through the menu selections:- The Cltr key gives the "Palettes" menu The Shift key gives the "Colours" menu The left Alt key gives the "Formulae" menu The right Alt key gives the "Main" menu Using the colour sliders Each individual colour can be set to any value using the Red / Green / Blue sliders. Click on the colour you wish to change in the palette strip and its current RGB values will be shown on the sliders. Click to the new values or hold the mouse button down and slide to the new values. The currently selected colour is indicated by a coloured block underneath it. The left and right arrows on the Amiga keyboard can be used instead of the mouse to select the colour from the palette strip. Selecting the picture box Some of the options apply to the currently selected picture box. The selected picture box has a thick border. The box may be selected by either clicking inside the box or by use of the keys "1", "2" and "3" on the keyboard. THE MAIN MENU (right Alt) F1 Plot / Pause / Resume - Picture generation control F2 About F3 Formulae Menu - Select new formula F4 Factors - Select scaling factor F5 Clear - Clear picture box F6 Load - Load previously saved pictures from disk F7 Save - Save current pictures to disk F8 Colours Menu - Play around with the colours F9 Cycle / Stop Cycle - Colour cycling F10 Quit Notes F1 displays "Plot" if no picture is being generated. When "Plot" is selected a new picture will be generated in the currently selected box. The menu option then changes to "Pause n" (where n is the box number). When "Pause n" is selected the generation will be suspended and the option will change to "Resume n". Selecting "Resume n" will resume the generation of the picture in box "n" (the one seleceted when the plot started) even though a different box may be currently slected. When the picture generation is complete the menu option will return to "Plot". When the plot is started the current formula and scaling factor will be displayed underneath the box (but not for NTSC verion - Soory). This will show the values used for the completed picture. When the formula (F3) or scaling factor (F4) are changed (before generating a new picture) these will be shown above the box. When the values are different then the values below the box apply to the displayed picture and the values above will be those used if "Plot" is selected. F3, F4 and F5 will apply to the currently selected box. When colour cycling is taking place (F9) it can be speeded up and slowed down by the up and down arrows on the Amiga keyboard. The down arrow key will change the cycle direction when the speed is minimum. FORMULAE MENU (left Alt) F1-F9 - Choose a new formula for the selected box. F10 Main Menu COLOURS MENU (Shift) F1 Swap - Swap two colours F2 Copy - Copy one colour value to another F3 Reverse - Reverse the colours in a specified range F4 Alternate - Alternate the colours in a specified range F5 Spread - Change the colours in the range to form a gradual spread from the first colour to the last F6 Repeat - Repeat the selected colour range through the whole palette F7 Palettes Menu - Select built-in palettes F8 Reverse All - Reverse the whole palette F9 Altern All - Alternate all the colours in the palette F10 Main Menu Notes F1 to F6 require a second colour to be selected. The mouse pointer will change to cross-wires and a second colour must be selected by clicking with the mouse before you can continue. PALETTES MENU (Ctrl) F1-F3 and F6-F8 :- Select a built-in Palette F4 Store - Stores the current palette for later restore (F9) F9 Restore - Restore the last stored (F4) palette F5 Colours Menu F10 Main Menu CREDITS and COPYRIGHT Written in AMOS Basic - AMOS (c) 1990 Mandarin/Jawx by Richard Kelly - 17 Birch Grove, Windsor, Berks, ENGLAND This program remains the copyright of Richard Kelly but may be freely copied and distributed subject to these conditions:- 1) All three files Sieve.Doc, Sieve.IFF and Sieve must be supplied unmodified. 2) No charge may be made other than nominal charges to cover costs of copying and distribution. The spirit is that it is Public Domain and profit making from its copying or distribution is not allowed. The program was developed and tested on the following configuration:- A500 1/2Mb expansion RAM GVP A500-HD+ with 2Mb RAM Workbench Version 1.3.2 AMOS Version 1.3 PAL monitor Bug reports and suggestions for changes are welcomed. Enjoy using the program.