Some questions about collideSprites...

vinicity

Thanks! I'll check it out!

Do you have any idea why c.a and c.b are returned from the function? Are they ever anything else than the two sprites supplied when calling the function?

Maxwello

@vinicity I think it's more a case of,
The function checks to see if 2 things are colliding. So what it returns is the position of those 2 things. Sprite a and b.. Or piggy one and piggy two if that is preferred. You just need a name to store it within.
That's what I think that is anyway.

Dave

You've actually caught Fuze at a bad time with that particular function page. There are errors on that page which really hurt.

I'll post here what is going to be included in an upcoming update to the help. This is what collideSprites() does:

collideSprites()

Description
Determine if two sprites have collided and optionally resolve the effect of the collision on their movement

Syntax

c = collideSprites( spriteA, spriteB )

c = collideSprites( spriteA, spriteB, resolve1, resolve2 )

Arguments

spriteA
Handle - Variable which stores the first sprite in the collision

spriteB
Handle - Variable which stores the second sprite in the collision

resolve1
Integer - True (1) if the first sprite can be moved by the collision, false (0) if not

resolve2
Integer - True (1) if the second sprite can be moved by the collision, false (0) if not

c
Array - List of structures detailing collision data. Properties listed below

c.exists
Integer - True (1) if collision occurred, false (0) if not

c.a
Handle - Variable which stores the first sprite in the collision

c.b
Handle - Variable which stores the second sprite in the collision

c.resolution_a
Vector - How sprite A was pushed during the collision { x, y }

c.resolution_b
Vector - How sprite B was pushed during the collision { x, y }

vinicity

Thanks a lot!
Much more helpful than the current help page...

vinicity

And just to confirm, c.a holds the same sprite as spriteA, and same for c.b and spriteB? This is just to make it convenient when processing the results?

Dave

@vinicity It'll be updated soon. In fact, I can tell you that a lot of big improvements to the help pages formatting and readability will be coming too :)

Until then, the incredible people on this website will put you right, I'm sure!

I'd also be happy to look at your specific case in detail.

Dave

@vinicity That is correct.

vinicity

Thank you very much! Looking forward to the updated documentation!

DomDom

This post is deleted!

vinicity

I did some more experimenting and it turns out that the c.resolution vectors are quite useful for implementing sprite bounce. I just normalized the vector and multiplied it with the desired velocity.

In my main loop I have two nestled for loops in order to monitor each possible collision with any two ships. So the collideSprite method is called 2450 times for each update(). For 50 ships this is pretty smooth, but if I increase the number of ships further, slowdown occurs... Kind of interesting.

Feel free to check out my little demo of 50 bouncing spaceships!
ID: NBYUXMND5C

vinicity

@DomDom said in Some questions about collideSprites...:

Collisions have 2 phases. Detection and Response. On first inspection, the collisionsprite function looks like it handles detection and provides the necessary info (in the form of the vectors you're talking about) to enable the programmer to implement the response as he sees fit. This would imply that you need to set the resultant velocities yourself.

Thanks, I gave it a try!

DomDom

This post is deleted!

vinicity

@DomDom said in Some questions about collideSprites...:

@vinicity Hope it helped.
By the way, checking collisions between 50 ships would only need 1250 checks if each ship only tests for collisions with the ships that are after it in a list.
Eg. something like
for sA=0 to Len(shipslist)-1
for sB= sA+1 to Len(shipslist)
C= checkcollisions(sA,sB)
Repeat
Repeat

Something else that might speed things up is to do a simple proximity check before the collision check.

Great point! I did not think of that, but in my defence I was kind of tired last night when I did the programming. Thanks!

vinicity

So I made a few changes and optimizations, and cleaned up the code. Fifty bouncing ships makes for a nice screensaver...

vinicity

I just shared a new version of my 50 bouncing ships demo. Cleaned up the code, added some optimizations to make it run smoother. Also made sure that ships that disappears at one edge are moved over to the other.

ID: NBYUXMND5C

vinicity

After some tweaking and with a proximity check in place, I managed to get 92 ships bouncing around without dropping from 60 fps! Success!

Dave

Awesome job @vinicity !

I'm glad to hear the info was helpful. Looking forward to seeing what you make in the future!

vinicity

Thanks! I am actually turning this into a game. I'll keep you posted once I got something new to show...

vinicity

@Dave said in Some questions about collideSprites...:

You've actually caught Fuze at a bad time with that particular function page. There are errors on that page which really hurt.

I'll post here what is going to be included in an upcoming update to the help. This is what collideSprites() does:

collideSprites()

Description
Determine if two sprites have collided and optionally resolve the effect of the collision on their movement

Syntax
c = collideSprites( spriteA, spriteB )

c = collideSprites( spriteA, spriteB, resolve1, resolve2 )
Arguments

spriteA
Handle - Variable which stores the first sprite in the collision

spriteB
Handle - Variable which stores the second sprite in the collision

resolve1
Integer - True (1) if the first sprite can be moved by the collision, false (0) if not

resolve2
Integer - True (1) if the second sprite can be moved by the collision, false (0) if not

c
Array - List of structures detailing collision data. Properties listed below

c.exists
Integer - True (1) if collision occurred, false (0) if not

c.a
Handle - Variable which stores the first sprite in the collision

c.b
Handle - Variable which stores the second sprite in the collision

c.resolution_a
Vector - How sprite A was pushed during the collision { x, y }

c.resolution_b
Vector - How sprite B was pushed during the collision { x, y }

It would be nice if the collideSprites() help page could be updated with the info above, since the info that is there now is not really helpful. I know you guys are super busy, but this is just a friendly reminder so you do not forget it!

waldron

@vinicity i only figured the sprite collision thing last week, before i was just using true/false didn't know you could link events triggers ect been a big 1 -UP for my code since