Multithreading problem

#1

HI,
i’m developing freehand drawing game, and in order to increase performance, i would use multithreading , i used this code:

void Canvas::onTouchMoved(cocos2d::Touch *touch, cocos2d::Event *event)  {
   auto t = std::thread(&Canvas::drawEvenlySpacedSprites, this,touch->getLocation(),touch->getPreviousLocation());
    t.detach();
}


void  Canvas::drawEvenlySpacedSprites(Vec2 start, Vec2 end) {
   // begin drawing to the render texture
    _target->begin();
    
     float distance = start.getDistance(end);
   if (distance > 1) {
    int d = (int)distance;

        for (int i = 0; i < d; i++)
        {
        float difx = end.x - start.x;
        float dify = end.y - start.y;
        float delta = (float)i / distance;

        Sprite * sprite = Sprite::create("brush3.png");
        sprite->setColor(Color3B::BLUE);
        sprite->setPosition(Vec2(start.x + (difx * delta), start.y + (dify * delta)));
        sprite->visit();
       
      }
     }

// finish drawing and return context back to the screen
_target->end();


  */
}

But I have this error :

libpng warning: iCCP: known incorrect sRGB profile
cocos2d: Assert failed: Cannot add command while rendering
Assertion failed: (!_isRendering), function addCommand, file         /Users/XXXXX/FreeDrawing/cocos2d/cocos/renderer/CCRenderer.cpp, line 268.

if i use t.join(); instead of t.detach(); , it work! , but it change the brush scale and the draw isn’t smooth
Help me please .
Thanks

#2

Any help please, i really need it :frowning:

#3

cocos2d-x is not multithreading safe.
when you call visit(), v3.x will add a command to render queue.

#4

Thanks, but is there any solution to do multithreading ?

#5

I think you should use a cpu algorithm, not use sprite render many times.

#6

I don’t understand you, please give me more details

#7

I believe that pushing rendering commands into separate threads won’t give you any performance gain. CPU multithreading would be effective if you’d use it for matrix calculations and similar tasks.

#8

Thanks, but why i can’t use global sprite in this section( i can in cocos2d-x v2.x)

Sprite * sprite = Sprite::create("brush3.png");
        sprite->setColor(Color3B::BLUE);
        sprite->setPosition(Vec2(start.x + (difx * delta), start.y + (dify * delta)));
        sprite->visit();

Please tell me how can i , improve this code