Climber Saver

Frequently Asked Questions

This document is Copyright © Paul Roberts 1999.

1. Do I have the latest version?
2. Where do I get the latest version?
3. How much does it cost?
4. Can you send me the latest version?
5. Is there a MAC/Unix/NeXTSTEP/BeOS version?
6. Do you have any other Screen Savers that you have written?
7. What do the two gauges/meters/green thingies in the top left corner mean?
8. Can we put your Screen Saver on our coverdisk?
9. Can we put your Screen Saver on our website?
10. Can I send copies to my friends?
11. Are you going to make a climbing game out of it?
12. It doesn't install on my machine. What is going wrong?
13. Does the climber ever fall?
14. Does the climber ever reach the top?
15. Can you give me advice on writing screen savers?
16. Are you aware that if you change the chalk bag colour to the same colour as the upper legs colour it looks rude?
17. What tools did you use to write it?
18. What algorithm do you use?

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1. Do I have the latest version?

   At the time of writing this Version 1 beta 9 was the latest version. Check on the website to find out.

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2. Where do I get the latest version?

   From my homepage. Specifically from http://www.homeusers.prestel.co.uk/cherryjam/utilities.html. There are various other sites that have it on them but that will always be the latest version.

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3. How much does it cost?

   It is free. I neither expect nor desire payment for it. In legalese.

   This program is licensed free of charge and can be freely distributed provided this file is distributed with it and that there are no charges beyond those necessary for administrative purposes.

   BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM "AS IS" WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

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4. Can you send me the latest version?

   Unfortunately not. I pay for my connection time and sending large binaries to a large number of people is not something I have any desire to do. It is available from my website. If for some reason you cannot download it ask someone who can.

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5. Is there a MAC/Unix/NeXTSTEP/BeOS version?

   There is currently a MAC version. Written by a colleague of mine as an afterdark module. It is available from the website. There are no immediate plans to support other OS's although as a NeXTSTEP user myself I am considering writing it as a backspace module.

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6. Do you have any other Screen Savers that you have written?

   Not at the moment. I did have but i lost them (they weren't any good anyway).

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7. What do the two gauges/meters/green thingies in the top left corner mean?

   Ok the one on the left is the total amount of "energy" that the climber has. The one on the right is a measure of the current "energy" use. This is determined entirely by posture (although dynos do use more). If the left hand bar drops to zero the climber falls. When he falls he then gets boosted back to a third on the assumption of an adrenaline rush or a tea break (your choice).

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8. Can we put your Screen Saver on our coverdisk?

   Absolutely. Yes. The more people that have it on their machines the better!.

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9. Can we put your Screen Saver on our website?

   Absolutely. Yes. The more people that have it on their machines the better!. You can either put a link to the zip file on my homepage or keep a copy on your own server. Your choice. If you do keep a copy can you try and ensure that it is uptodate. The only caveat I would impose is that you don't try and pass it off as your own work.

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10. Can I send copies to my friends?

    Absolutely. Yes. The more people that have it on their machines the better!.

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11. Are you going to make a climbing game out of it?

    I have thought of this. No. there are several out there and they are better than anything that this could be turned into. Crank up your search engines and look. There are a few java ones and a DOS based game that I found.

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12. It doesn't install on my machine. What is going wrong? Without more information than this i can't help. What is likely is that you extracted the scr file right clicked on it and selected install. This doesn't do what you might expect. This is nothing to do with me. You need to copy or move the scr file into your windows\system directory or on NT your windows\system32 directory.

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13. Does the climber ever fall?

    Wait and see.

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14. Does the climber ever reach the top?

    Wait and see.

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15. Can you give me advice on writing screen savers?

    My only advice is go for it. No area of programming is trivial, this is also true of writing screensavers.

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16. Are you aware that if you change the chalk bag colour to the same colour as the upper legs colour it looks rude?

    I wasn't. I am now. Urm I don't know what to say.

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17. What tools did you use to write it?

    It was written entirely in C. Using Microsoft's Visual C.
    

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18. What algorithm do you use.

    The climber searches for the best possible move for each hand and foot, these are constrained by the following rules.

    1. the move must be within reach
    2. the climber's feet aren't allowed higher than his hips (if i can't get my feet higher than my hips i don't see why i should let my screensaver (the real reason is to stop him inverting))
    3. left hand moves must be to the left of the right hand and vice versa, same with feet
    4. not allowed to put both hands or both feet on the same hold (hands and feet on the same hold aren't allowed either) if the hold is a ledge or a crack then this restriction doesn't count.

    when there is a best move for each limb then the best of those four is chosen with the following restrictions

    1. move duplication is forbidden within the last 10 moves (to stop loops of moves occurring)
    2. if there is no move available, or the total gain of the last 5 moves was negative then he attempts to dyno

    to dyno he finds the nearest hold above and between his hands. If this hold is within the distance allowed for a dyno then he heroicly leaps for this new hold with both hands, if there is no hold available he falls.

    If he falls three times on a given cragg then a new cragg is generated.

    The climbers attitude, or stance, is calculated from the position of hands and feet as follows.

    • The average of the four extremeties is calculated. A line is projected from this position parrallel to a line between the average hand position and the average foot position. This is the line that the climbers spine will lie on.
    • Circles are drawn from each hand with radius of the maximum arm extension, for each of these circles the lower intersection with the spine is found. The higher of these two intersections is the upper limit that the shoulder can be.
    • The same is done for the feet to find the lower limit of the pelvis position.
    • The shoulder limit and pelvis limit are averaged together to find the centre of the spine. the shoulder-girdle and pelvis are positioned equal distances above and below this respectively. The shoulders and hips are perpendicular to the spine.
    • given the shoulder and hip positions and the positions of the hands and feet the elbows, and knees are found by intersecting circles of the appropriate lengths. i.e. from the left hand a circle of radius forearm length is intersected with a circle projected from the left shoulder of radius upperarm length. The _left_ intersection is chosen. If there is no intersection the the elbow or knee is placed at the midpoint and the attitude is flagged as invalid (this means that if necessary the climber can be drawn in an _unnatural_ posture, but that such postures are avoided where possible)
    • The feet are projected from the foot position (actually the position of the heel) parralel to the hips (this is the biggest bug IMO about the climbers positioning, he stands exclusively on his heels, not his toes)
    • The head is positioned at the end of the neck (projected out from the spine), the head is always vertical.

    When the climber moves the positions of his hands and feet are interpolated from one position to the next, the attitude (position of elbows and knees etc) is caluclated for each of these interpolations, so his whole body adjusts even as jsut one limb is moved.

    The simple skeleton i use has the following proportions

    lowerLeg	35
    upperLeg	35
    pelvis	20
    torso	45
    shoulder	30
    upperArm	30
    lowerArm	25
    neck	14
    skullWidth	15
    skullHeight	20