CODEWITHSUNDEEP
objective-cioscocos2d-iphone
user1437403
user1437403

Reputation: 129

draw with opengl less than every frame

Is their any way, in cocos2d, to have a cclayer draw via opengl less frequently than every frame? I have tried:

-(void) draw
{
     glEnable(GL_LINE_SMOOTH);
     if (iShouldUpdate) {
         ccDrawLine(ccp(50,50), ccp(200,200));   
         iShouldUpdate = false;
     }
}

-(void) updateTheMap
{
     iShouldUpdate = true;
}

and then call: updateTheMap whenever needed, but it just displays for 1 frame.

Thanks.

Upvotes: 2

Views: 361

Answers (1)

CodeSmile
CodeSmile

Reputation: 64477

Yes and no.

Normally the frame contents are cleared before a new frame renders. Every frame begins at a clean state. Now if you were to disable clearing of the screen, you could draw something once and it would stay on screen. But then you wouldn't be able to move what you've drawn without clearing exactly just the parts that you've drawn.

Since this gets overly complex and error prone really quickly, the standard way for games has been ever since there are game engines to clear the frame contents before beginning to draw a new frame. One notable exception being DooM, where it was assumed by the engine developer that every pixel on screen would be updated every frame - unless there were missing textures in which case you could see the famous Halls of Mirrors (HOM) effect that occurs when you're not clearing the framebuffer every frame:

enter image description here

So the standard is to draw the entire screen contents again every frame. Because of that, you can't draw something just every couple of frames because if you do that, then whatever you've drawn will be visible on screen for one frame and then it'll be gone.

In summation: you have to draw everything that should be visible on screen repeatedly every frame. That's the way almost all game engines work.

Upvotes: 1

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