cocos2d-x v3 c++ Drop shadow cocos2d::Sprite - c++

Question

As far as I've found out, cocos doesn't offer a simple filter handling like AS3 for example does.
My situation:
I want to add a realtime shadow to an cocos2d::Sprite.
For example I would like to do something like this (similar to AS3):
auto mySprite = Sprite::createWithSpriteFrameName("myCharacter.png");
DropShadowFilter* dropShadow = new DropShadowFilter();
dropShadow->distance = 0;
dropShadow->angle = 45;
dropShadow->color = 0x333333;
dropShadow->alpha = 1;
dropShadow->blurX = 10;
dropShadow->blurY = 10;
dropShadow->strength = 1;
dropShadow->quality = 15;
mySprite->addFilter(dropShadow);
This should add a shadow to my Sprite to achieve an result like this:
Adobe Drop Shadow Example
Could you help me please?

Answer 1

There isn't any built in support for shadows on Sprites in Cocos2D-X.
The best option, performance-wise, would be to place your shadows in your sprite images already, instead of calculating and drawing them in the code.
Another option is to sub-class Sprite and override the draw method so that you duplicate the sprite and apply your effects and draw it below the original.
One possible way to achieve that is with this snippet from this thread on the Cocos forum. I can't say that I completely follow what this code does with the GL transforms, but you can use this as a starting point to experiment.
void CMySprite::draw()
{
// is_shadow is true if this sprite is to be considered like a shadow sprite, false otherwise.#
if (is_shadow)
{
ccBlendFunc blend;
// Change the default blending factors to this one.
blend.src = GL_SRC_ALPHA;
blend.dst = GL_ONE;
setBlendFunc( blend );
// Change the blending equation to thi in order to subtract from the values already written in the frame buffer
// the ones of the sprite.
glBlendEquationOES(GL_FUNC_REVERSE_SUBTRACT_OES);
}
CCSprite::draw();
if (is_shadow)
{
// The default blending function of cocos2d-x is GL_FUNC_ADD.
glBlendEquationOES(GL_FUNC_ADD_OES);
}
}