Here’s a quick reference for those of you making timelapse videos this year.

Hungry Derivatives Advancing Collapse :: LD14 :: by jph/2009

here is the title sceen in the ZGE editor,. .

Well that was fun!  My first LD!

This game is not at all what I had in mind at the start,. but I tend to wander as new ideas come in,. . sotra’ cool, very odd.  What you think?

http://iterationgames.com/bamboo/jph_LD14__Hungry_Derivatives_013.zip

(win xp/vist ver. 47kb)  osX and linux possible if wanted,. .

I had some fun working with the Implicit mesh procedures to build the block head character,. something I have not used so much in the ZGE till now,.   I just was not able to get the sort of collision reactions I indended working in this time line,. my lazy math/logic skills,. and without resorting to my normal method of asking my friends for help with math and logic,. so this is me solo., I will likely do a game that I did have in mind later with that help,. .

This is a weird game!  I am not sure many people will enjoy it,. but give ‘er a go and let me know your thoughts,. I do enjoy feedback.  there is a simple score and it is currently a player vs environment with no bad guys as I had inended,. but 48 hours is not that much time and it was only the time in that window I could actualy use working on it so much less ,. . I’m sure that is true for most here.  so the level just gets less dense and you will eventually miss a jump and fall,.  .  so get as much shiny befor that as you can.

My solution:

So the problem is to figure out the direction a player (moving in 3-d) has to shoot to hit an enemy (also moving in 3-d) given their positions, velocities, and the speed of the bullet.

The approach I used was to solve the equation

time it takes the enemy to reach a position = time it takes the bullet to reach the position

for the time.

First, redefine the vectors so that they are all relative to the player. This
leaves you with only bullet speed, enemy velocity, and enemy position. The
points in question are the points along the enemy’s trajectory, so express the
above equation in terms of t:

This can be solved with the quadratic equation:

Note that there may be zero, one, or two solutions. Negative solutions reflect hits in the past. If there are no positive solutions it is not possible for the player to hit the enemy.

Once you have t, it is simple to calculate the position.

Edit: forgot the exponent on the bottom of the final answer.

Someone (partly me) derailed the IRC into wild discussion of a math problem. I think some 5-6 people were involved at some points, and we still haven’t arrived at a conclusion as far as I can tell.

Here’s an image I cooked up to help visualize the problem:

The problem is deceptively simple: Determine what angle to fire a bullet in, if it is to hit a target that’s moving past you at a constant velocity. In other words, both objects are moving at a fixed speed, and you just have to figure out in what direction to launch the bullet so that it’ll hit the target perfectly. Iterative solutions need not apply. Good luck with interpreting the image, it’s pretty confus(ed/ing).