Game Development

Q: Why does my position interpolation code result in "jumpy" motion?

11:16 AM

can anyone please help me with this:

I am developing an android game with box2d and use a fixed timestep system for advancing the physics. However as I use this system it requires the box2d positions to be interpolates. I read this article and have implemented an interpolation method very much like the one in the article. The meth...

Martin Sojka

Sorry, I'm not knowledgable enough in Android development or box2d, and the others aren't on ATM, it seems. They'll check and answer if they can later, I guess.

OK thanks :)

5 hours later…

Gilson

4:17 PM

test

Hey

Hello

heh, Gilson and I are gonna talk about network time syncing and network programming in an other room, :)

5:00 PM

Could someone perhaps help with this question please? - the given solution is incorrect. gamedev.stackexchange.com/questions/18724/…

@Jason I'm assuming that smoothStates_ gets called on every frame?

yep

How have you proven that the given solution is incorrect?

More specifically, how long does it take to run through smoothStates_() on the Android?

I have increased the FIXED TIME and have run the game on pretty fast phones - galaxy s and s 2

Could it be that even those fast phones aren't fast enough for what you're trying to do?

5:10 PM

no have a very simple scene with only about 8 objects getting smoothed

even on slow phones it should be fine

Jimmy

can you slow down the framerate on the PC version to reproduce the effect?

errm I would have to think of a way to do that

libdgx is what i use and it calles render frame as fast as possible I gues I could add a sleep to the render() function

From the logs, it looks like the interpolated position is moving at ~0.35 units per frame...what does that mean, exactly?

Jimmy

I'm just curious, because it could be something that is a bug in the calculation but when the frame rate is high, the movement deltas are so small you can't see the error visually

The position calculation is with box2d not my calculation - and in this case it's just a bunch of falling objects

0 is the floor so it moves 0.35 towards the floor

if that's what you meant

@Jimmy adding a sleep to slow done the framerate does cause the same effect

5:52 PM

pastebin.com/GYLVWapz

I made a new log with position diff

something odd is going on.. sometimes the diff is negative and sometimes positive - it should be the same as the object is falling

6:11 PM

Well, that would be the cause of the jumpy motion, though exactly what's causing it is hard to say. </obvious>

Well I want to implement the tron like glowing effect on the edges of a rectangle. I know that I have to use the bloom effect to achieve it.Could you suggest me a good tutorial..

hehe yep the cause is what I am chasing

@noddy language? platform? i could probably find a tutorial for bloom effects in flash but that's useless if you're using c++ and SDL

well i am using c++ and openGL

thus I want a shader in glsl or vert and frag format..

I remember seeing a glowing lighting strike tutorial but can't seem to find it now

6:41 PM

could some one help me with the full screen anti aliasing in opengl?

@noddy "Can" :P

user4704

There are several questions on this site about bloom

user4704

I listed a few in the comment of your recent question (which I also flagged to close as a dupe)

@JoshPetrie and none of them has satisfactory answers

they mostly lack examples and implementations

user4704

6:46 PM

the question is still a duplicate

yeah your point is correct!

probably you can create wiki entry for bloom effect

a lot of people are using this effect in their games

user4704

There isn't really a wiki on here. Except for the tag wikis, which are more about describing the tag

@snape this has a bloom shader for glsl: myheroics.wordpress.com/2008/09/04/glsl-bloom-shader

yeah i used that but it is actually not a bloom shader

it is somewhat like fuzzy shading

user4704

A problem with looking for concrete examples is that most shaders for interesting effects have ties and/or assumptions about the CPU-side data format and such.

user4704

6:52 PM

Rarely, if ever, are they drop-in usable

there's also a possibly more detailed bloom shader tutorial here: prideout.net/archive/bloom

user4704

So it's better to just understand the theory and build the effect on your own