Rotate sprite image according to user touch location?

Question

I m start learning game development. As a beginner i create one demo game in which one cannon hit bullets to the enemies (coming toward cannon from different direction). Now i stuck on cannon sprite image rotation anywhere user touch on the screen or enemies. How i do that, My initial code as following,

void HelloWorld:: ccTouchesBegan(CCSet *touches, CCEvent * event)
{
    CCSize winSize = CCDirector::sharedDirector()->getWinSize(); 
    CCTouch* touch = (CCTouch*)( touches->anyObject() );
    CCPoint location = touch->locationInView(touch->view());
    location = CCDirector::sharedDirector()->convertToGL(location);

    //Rotate cannon direction toward touch point
    CCPoint diffPoint = ccpSub(_cannonImage->getPosition(), location);
    float angleRadians = atanf((float)diffPoint.y/(float)diffPoint.x);
    float angleOffset = CC_DEGREES_TO_RADIANS(180);

    if(diffPoint.x < 0){
        angleRadians += angleOffset;
    }else{
        angleRadians -= angleOffset;
    }

    CCLog("angle to be rotate = %f", angleRadians);

    _cannonImage->runAction(CCRotateBy::actionWithDuration(0.1, angleRadians));

}

The code is written in cocos2d-x . I also accepting answer by someone who written in plain cocos2d.

Thanks iHungry

Rovelli

would be helpful if you mentioned what exactly is the problem with this code? Btw, check out ccpAngle and ccpAngleSigned, if they're available in cocos2d-x. – Miscible

@LearnCocos2D, yes boss ... it working but it not rotate that i want.... – Rovelli

i m also checking changing angle.... but its not working .... the actual problem is that... the image rotating lazily and in small angle.... i want set cannon face toward the user touch location. – Rovelli

Answer 1

First of all, replace

float angleRadians = atanf((float)diffPoint.y/(float)diffPoint.x);
float angleOffset = CC_DEGREES_TO_RADIANS(180);

if(diffPoint.x < 0){
    angleRadians += angleOffset;
}else{
    angleRadians -= angleOffset;
}

by

float angleRadians = atan2f(diffPoint.y, diffPoint.x);

Then it would be better to set rotation immediately (without actions) to process multiple frequent touches.

_cannonImage->setRotation(angleRadians);

Maybe you will need to adjust rotation like setRotation(-angleRadians) or setRotation(angleRadians+90) - it depends on your coordinate system.

Riorsson

In my code I had to switch x and y to atan2f(diffPoint.x, diffPoint.y); and setRotation(angleRadians/M_PI * 180); – Heppman

Answer 2

The perfect answer as follows,

float HelloWorld::changingAngleAccordingToCoordinateSystem(CCPoint imageCenter, CCPoint touchLocation, float calculatedAngle){

//Consideration :- all Angles is in Degree 
if((calculatedAngle >= 0 && calculatedAngle <= 90) || (calculatedAngle >= 90 && calculatedAngle <= 180)){
    //Ist quardant
    calculatedAngle = calculatedAngle;
}
else if(calculatedAngle < 0 && calculatedAngle >= -90){
    //IInd quardant
    calculatedAngle = 270 + (90 + calculatedAngle);
} 
else if(calculatedAngle < -90 && calculatedAngle >= -180){
    calculatedAngle = 180 + (180 + calculatedAngle);
}

return calculatedAngle;
}


//Rotate cannon direction toward touch point
float diff_X = touchLocation.x - myImage->getPosition().x;
float diff_Y = touchLocation.y - myImage->getPosition().y;
CCPoint diffPoint = CCPoint(diff_X, diff_Y);
float angleRadians = atan2f(diffPoint.y,diffPoint.x);
angleRadians = CC_RADIANS_TO_DEGREES(angleRadians);
angleRadians = HelloWorld::changingAngleAccordingToCoordinateSystem(myImage->getPosition(), touchLocation, angleRadians);
myImage->setRotation(-angleRadians);

Rovelli

Answer 3

i used this code to rotate my sprite. i Was moving the sprite according to my accelerometer reading.

float angleRadians =-accelX;
float angleDegrees = CC_RADIANS_TO_DEGREES(angleRadians);
objGlider->sprite_Glider.rotation = cocosAngle;

Check it. The reason of slow may be that you may be using CClog or NSLog in the code.

Here goes the complete code.

if(!boolPlayerDied)
{
    static float prevX=0, prevY=0;
    #define kFilterFactor 1.0f// don't use filter. the code is here just as an example
    float accelX = (float) acceleration.x * kFilterFactor + (1- kFilterFactor)*prevX;
    float accelY = (float) acceleration.y * kFilterFactor + (1- kFilterFactor)*prevY;
    prevX = accelX;
    prevY = accelY;
    accelX = accelX-0.5;// Angle check fot tgfor the player to play
    float angleRadians =-accelX;
    float angleDegrees = CC_RADIANS_TO_DEGREES(angleRadians);
    if(accelX>0)
    {
        cocosAngle = 1.1 * angleDegrees;
    }
    else
    {
        if(accelX<-0.5)
            accelX=-0.5;
        cocosAngle = 1.1  * angleDegrees;
    }
    objGlider->sprite_Glider.rotation = cocosAngle;
}

objGlider is the object of the class which creates glider sprite and sprite_Glider is the sprite used in glider class.

you can use rotation property with your sprite to be rotated. In cocos2Dx it might be setRotation.

Backpack

can u provide me your brief code becoz i m not understanding the term of sprite_Glider.rotation...... Even though cocos2dx not accepting dot (.) syntax for rotation... we have to used either CCRotateBy or CCRotateTo classes. – Rovelli

Yes Ur code also proper but accepted code work for me. I only give you up-vote for it. – Rovelli

No worries. Just one question. using setRotation property with sprite, did it worked in cocos2D-x ?? – Backpack