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Draw objects in real time


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#1 vir2007   Members   -  Reputation: 105

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Posted 01 August 2012 - 12:33 PM

Hi all,

I have glutDisplayFunc() to draw the environement

And I receive data from network that contain position of objects, I have a thread that treats that kind of data

So here my problem

I tried to store data into vector<data> to be drawn in glutDisplayFunc each time, this way slow down my computer and moving objects is not smoothly

Then I tried to not use vector<data> and want to draw objects direclty from "thread" that receive data, and nothing happened

so is there way to make moving objects in real time, and if possible draw them from that thread instead of glutDisplayFunc

Thanks

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#2 uwi2k2   Members   -  Reputation: 771

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Posted 02 August 2012 - 01:26 AM

hi,

first of all make sure you are not reciving data by TCP/IP... as this may be to slow for real time Game.
Use UDP instead.
But the basic setting is right. the Network Thread should write to a Object or what ever is your data container.
And than inside your glutDisplayFunc() you just draw as you would always do ...
You may track how many times per second you update the data from network .... as this needs to be close to your framerate .

cu
uwi2k2
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#3 darookie   Members   -  Reputation: 1437

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Posted 03 August 2012 - 01:04 PM

so is there way to make moving objects in real time, and if possible draw them from that thread instead of glutDisplayFunc

This is not possible because all rendering has to happen within the thread of the OpenGL context. First you need to ensure that the access to the data received from the network thread happens in a synchronised way. Otherwise all kinds of funny effects may occur due to concurrency issues.

You can achieve this by various methods such as employing the producer-consumer-pattern (the network thread would represent the producer role and your rendering thread would be the consumer role).

The term "real-time" must be treated in a relative way when dealing with network communication, due to the fact that network connections are prone to lag for various reasons. You can compensate for this by using motion vectors and prediction algorithms instead of absolute object positions.

Take for example a car. Instead of updating the car's position on the server side and transmitting its updated position, you can instead transmit a movement vector along with the current velocity. This way you can update the car's position on the client side in real time while waiting for updated information (like vector or velocity changes) from the network. In order to keep things synchronised you can also throw in a full state after a certain number of packets to force the client side to update the actual position, for example.

Note, however, that it's far from trivial to achieve satisfying results - a good real time solution can be quite a challenge.

#4 vir2007   Members   -  Reputation: 105

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Posted 04 August 2012 - 03:24 PM

I was making some mistakes which are corrected now, thnx for help anyway :)

@darookie: thnx for that explanations :)

Edited by vir2007, 04 August 2012 - 03:26 PM.





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