游戏开发中,普通的碰撞检测就简单了,这主要是借助于精灵类的boundingBox矩形间是否相交来判定。但试想,如果在一个游戏中存在多种粒子武器,这两种武器互相朝对方开火,那么也应当存在一个粒子***相交(即碰撞)的问题吧。这时候如何检测呢?
今天在整理COCOS2D-X粒子系统支持时发现了这样的问题,而且碰到一个函数updateQuadWithParticle。这个函数在基类CCParticleSystem中定义如下:
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void
CCParticleSystem::updateQuadWithParticle(tCCParticle* particle,
const
CCPoint& newPosition)
{
CC_UNUSED_PARAM(particle);
CC_UNUSED_PARAM(newPosition);
// should be overridden
}
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而在上述基类CCParticleSystem的子类CCParticleSystemQuad中有如下实现代码:
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void
CCParticleSystemQuad::updateQuadWithParticle(tCCParticle* particle,
const
CCPoint& newPosition)
{
ccV3F_C4B_T2F_Quad *quad;
if
(m_pBatchNode)
{
ccV3F_C4B_T2F_Quad *batchQuads = m_pBatchNode->getTextureAtlas()->getQuads();
quad = &(batchQuads[m_uAtlasIndex+particle->atlasIndex]);
}
else
{
quad = &(m_pQuads[m_uParticleIdx]);
}
ccColor4B color = (m_bOpacityModifyRGB)
? ccc4( particle->color.r*particle->color.a*255, particle->color.g*particle->color.a*255, particle->color.b*particle->color.a*255, particle->color.a*255)
: ccc4( particle->color.r*255, particle->color.g*255, particle->color.b*255, particle->color.a*255);
quad->bl.colors = color;
quad->br.colors = color;
quad->tl.colors = color;
quad->tr.colors = color;
// vertices
GLfloat size_2 = particle->size/2;
if
(particle->rotation)
{
GLfloat x1 = -size_2;
GLfloat y1 = -size_2;
GLfloat x2 = size_2;
GLfloat y2 = size_2;
GLfloat x = newPosition.x;
GLfloat y = newPosition.y;
GLfloat r = (GLfloat)-CC_DEGREES_TO_RADIANS(particle->rotation);
GLfloat cr = cosf(r);
GLfloat sr = sinf(r);
GLfloat ax = x1 * cr - y1 * sr + x;
GLfloat ay = x1 * sr + y1 * cr + y;
GLfloat bx = x2 * cr - y1 * sr + x;
GLfloat by = x2 * sr + y1 * cr + y;
GLfloat cx = x2 * cr - y2 * sr + x;
GLfloat cy = x2 * sr + y2 * cr + y;
GLfloat dx = x1 * cr - y2 * sr + x;
GLfloat dy = x1 * sr + y2 * cr + y;
// bottom-left
quad->bl.vertices.x = ax;
quad->bl.vertices.y = ay;
// bottom-right vertex:
quad->br.vertices.x = bx;
quad->br.vertices.y = by;
// top-left vertex:
quad->tl.vertices.x = dx;
quad->tl.vertices.y = dy;
// top-right vertex:
quad->tr.vertices.x = cx;
quad->tr.vertices.y = cy;
}
else
{
// bottom-left vertex:
quad->bl.vertices.x = newPosition.x - size_2;
quad->bl.vertices.y = newPosition.y - size_2;
// bottom-right vertex:
quad->br.vertices.x = newPosition.x + size_2;
quad->br.vertices.y = newPosition.y - size_2;
// top-left vertex:
quad->tl.vertices.x = newPosition.x - size_2;
quad->tl.vertices.y = newPosition.y + size_2;
// top-right vertex:
quad->tr.vertices.x = newPosition.x + size_2;
quad->tr.vertices.y = newPosition.y + size_2;
}
}
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上述函数咱就不深入分析了,因为涉及到许多的OpenGL ES概念。但是,从名义上可以看出,其作用是使用当前粒子相关信息来更新quad数据(这个quad与三维场景下基本图元有关,一般在渲染三维物体时使用三角形图元及四边形图元等表示方法)。而我们通过把自己的武器类继承自CCParticleSystemQuad类,并重载这个函数,就可以取得这个粒子数据(当然,对于一个粒子系统来说,不止是一枚粒子了)。然后,通过类似于引文中的方法,如下:
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void
TTMyParticleWeapon::updateQuadWithParticle( tCCParticle* particle,
const
CCPoint& newPosition )
{
CCParticleSystemQuad::updateQuadWithParticle(particle, newPosition);
if
(!
this
->isVisible())
return
;
CCPoint pos =
this
->convertToWorldSpace(particle->pos);
/// 碰撞检测 。。。。。
}
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来实现自己的粒子武器之间的碰撞检测了!
参考文章:
http://blog.csdn.net/jebe7282/article/details/8486822
本文转自朱先忠老师51CTO博客,原文链接:http://blog.51cto.com/zhuxianzhong/1551635 ,如需转载请自行联系原作者