用cocos2d-x 实现UV动画--实现篇
UVSprite
uv动画是指通过在程序运行时动态改变纹理坐标，实现动态效果的纹理动画，使用uv动画可以实现水流动，火焰燃烧等效果。
下图是UVSprite实现的一个动画效果
本文由liangneo原创，转载请保留原文地址 ：http://blog.csdn.net/liangneo/article/details/42583533
1.分析
我们需要的是一个具uv动画的sprite，最简单合理的方式是让你UVSprite直接继承于CCSprite，另外我们还需要两个变量来控制U或V方面是否需要动画，另外两个变量来控制U和V方向的动画速度，因此UVSprite类的声明如下：
class UVSprite : public cocos2d::CCSprite
{
//U方向是否需要动画
bool _AutoScrollU = true;
//U方面动画速度（0~~1）
float _AutoScrollSpeedU =0;
//V方向是否需要动画
bool _AutoScrollV = false;
//V方向的动画速度（0~~1）
float _AutoScrollSpeedV=0;
//保存当前已经移动的uv值
float _AutoScrollCountU=0;
float _AutoScrollCountV=0;
};
另外我们还需要两个接口来创建UVSprite和CCSprite保持一致：
//从plist中的frame创建
static UVSprite* createWithSpriteFrameName(const char *pszSpriteFrameName);
//从贴图文件直接创建
static UVSprite* create(const char *pszFileName);
另外我们还需要一个update来更新uv的偏移值：
void UVSprite::update(float dt)
{
CCSprite::update(dt);
//更新u
if(_AutoScrollU)
{
_AutoScrollCountU += dt * _AutoScrollSpeedU;
}
//更新v
if (_AutoScrollV) {
_AutoScrollCountV += dt * _AutoScrollSpeedV;
}
//如果超出范围从0开始
if (_AutoScrollCountU > 1 || _AutoScrollCountU < -1) {
_AutoScrollCountU = 0;
}
if (_AutoScrollCountV > 1 || _AutoScrollCountV < -1) {
_AutoScrollCountV = 0;
}
}
上一篇文章中我们提到，uv的值在(0~~1)范围内，因此在更新时确保偏移在（-1，1）范围内
2.shader
a.有了更新uv的更新我们来写shader,顶点shader我们使用cocos2d提供的 ccPositionTextureColor_vert，代码如下
attribute vec4 a_position;
attribute vec2 a_texCoord;
attribute vec4 a_color;
#ifdef GL_ES
varying lowp vec4 v_fragmentColor;
varying mediump vec2 v_texCoord;
#else
varying vec4 v_fragmentColor;
varying vec2 v_texCoord;
#endif
void main()
{
gl_Position = CC_MVPMatrix * a_position;
v_fragmentColor = a_color;
v_texCoord = a_texCoord;
}
b.片元shader,在片元shader中我们需要更新uv坐标，设置一个变量texOffset来表示uv的偏移，代码如下:
#ifdef GL_ES
precision lowp float;
#endif
varying vec4 v_fragmentColor;
varying vec2 v_texCoord;
uniform vec2 texOffset;
uniform sampler2D CC_Texture0;
void main()
{
vec2 texcoord = mod(texOffset+v_texCoord,1.0);
gl_FragColor = v_fragmentColor * texture2D(CC_Texture0, texcoord);
}
在片元Shader中，我们将默认的v_texCoord加上传进来的texOffset,并对结果与1求模，确保纹理坐标出界后回到合理的位置
3.shader加载，为UVSprite添加一个成员函数，和一个shader中texOffset的uniform引用,代码如下：
void UVSprite::loadShaderVertex(const char *vert, const char *frag)
{
CCGLProgram *shader = new CCGLProgram();
shader->initWithVertexShaderByteArray(vert, frag);
shader->addAttribute(kCCAttributeNamePosition, kCCVertexAttrib_Position);
shader->addAttribute(kCCAttributeNameColor, kCCVertexAttrib_Color);
shader->addAttribute(kCCAttributeNameTexCoord, kCCVertexAttrib_TexCoords);
shader->link();
shader->updateUniforms();
_uniformOffset = glGetUniformLocation(shader->getProgram(), "texOffset");
this->setShaderProgram(shader);
shader->release();
}
在该函数中，首先加载sahder,添加cocos2dx提供三个默认属性，分别是点坐标，点颜色，点的uv坐标，然后获取texOffset在shahder中的uniform引用
4.渲染，重写CCSprite的draw函数，除了实现CCSprite的draw的渲染功能，还额外的绑定texOffset,代码如下：
void UVSprite::draw()
{
CC_PROFILER_START_CATEGORY(kCCProfilerCategorySprite, "CCSprite - draw");
CCAssert(!m_pobBatchNode, "If CCSprite is being rendered by CCSpriteBatchNode, CCSprite#draw SHOULD NOT be called");
getShaderProgram()->use();
getShaderProgram()->setUniformsForBuiltins();
ccGLBlendFunc( m_sBlendFunc.src, m_sBlendFunc.dst );
//绑定texOffset
getShaderProgram()->setUniformLocationWith2f(_uniformOffset, _AutoScrollCountU, _AutoScrollCountV);
//绑定纹理贴图
ccGLBindTexture2D( m_pobTexture->getName() );
ccGLEnableVertexAttribs( kCCVertexAttribFlag_PosColorTex );
#define kQuadSize sizeof(m_sQuad.bl)
#ifdef EMSCRIPTEN
long offset = 0;
setGLBufferData(&m_sQuad, 4 * kQuadSize, 0);
#else
long offset = (long)&m_sQuad;
#endif // EMSCRIPTEN
// 设置渲染坐标(x,y)
int diff = offsetof( ccV3F_C4B_T2F, vertices);
glVertexAttribPointer(kCCVertexAttrib_Position, 3, GL_FLOAT, GL_FALSE, kQuadSize, (void*) (offset + diff));
// 设置纹理坐标(u,v)
diff = offsetof( ccV3F_C4B_T2F, texCoords);
glVertexAttribPointer(kCCVertexAttrib_TexCoords, 2, GL_FLOAT, GL_FALSE, kQuadSize, (void*)(offset + diff));
// 设置顶点颜色
diff = offsetof( ccV3F_C4B_T2F, colors);
glVertexAttribPointer(kCCVertexAttrib_Color, 4, GL_UNSIGNED_BYTE, GL_TRUE, kQuadSize, (void*)(offset + diff));
//渲染矩形
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
CHECK_GL_ERROR_DEBUG();
#if CC_SPRITE_DEBUG_DRAW == 1
// draw bounding box
CCPoint vertices[4]={
ccp(m_sQuad.tl.vertices.x,m_sQuad.tl.vertices.y),
ccp(m_sQuad.bl.vertices.x,m_sQuad.bl.vertices.y),
ccp(m_sQuad.br.vertices.x,m_sQuad.br.vertices.y),
ccp(m_sQuad.tr.vertices.x,m_sQuad.tr.vertices.y),
};
ccDrawPoly(vertices, 4, true);
#elif CC_SPRITE_DEBUG_DRAW == 2
// draw texture box
CCSize s = this->getTextureRect().size;
CCPoint offsetPix = this->getOffsetPosition();
CCPoint vertices[4] = {
ccp(offsetPix.x,offsetPix.y), ccp(offsetPix.x+s.width,offsetPix.y),
ccp(offsetPix.x+s.width,offsetPix.y+s.height), ccp(offsetPix.x,offsetPix.y+s.height)
};
ccDrawPoly(vertices, 4, true);
#endif // CC_SPRITE_DEBUG_DRAW
CC_INCREMENT_GL_DRAWS(1);
CC_PROFILER_STOP_CATEGORY(kCCProfilerCategorySprite, "CCSprite - draw");
}
代码的功能和CCSprite的draw基本一致，唯一的差别如下：
//绑定texOffset
getShaderProgram()->setUniformLocationWith2f(_uniformOffset, _AutoScrollCountU, _AutoScrollCountV);
该行代码将shader中的texOffset与update中的实时更新的uv关联起来。
本文源代码下载地址： http://download.csdn.net/detail/liangneo/8348147
使用说明：放到cocos2d-x的samples/Cpp/目录下替换原来的文件即可
bugFix,由于cocos2d-x的spriteFrame可能只使用贴图中的一部分，因此使用UVSprite::createWithSpriteFrameName创建出来的对象的uv只是0 --- 1范围中的一部分，使用上述shader可以会出错。作以下更正：
1.frag Shader
#ifdef GL_ES
precision lowp float;
#endif
varying vec4 v_fragmentColor;
varying vec2 v_texCoord;
uniform vec2 texOffset;
uniform sampler2D CC_Texture0;
uniform vec2 uRange;
uniform vec2 vRange;
void main()
{
vec2 texcoord = texOffset+v_texCoord;
texcoord.x = mod(texcoord.x - uRange.x,uRange.y-uRange.x) + uRange.x;
texcoord.y = mod(texcoord.y - vRange.x,vRange.y-vRange.x) + vRange.x;
gl_FragColor = v_fragmentColor * texture2D(CC_Texture0, texcoord);
}
增加了两个变量，uRange和vRange分别用来记录，uv的范围，确保精灵在的贴图在这个范围内
2.shader Load
void UVSprite::loadShaderVertex(const char *vert, const char *frag)
{
CCGLProgram *shader = new CCGLProgram();
shader->initWithVertexShaderByteArray(vert, frag);
shader->addAttribute(kCCAttributeNamePosition, kCCVertexAttrib_Position);
shader->addAttribute(kCCAttributeNameColor, kCCVertexAttrib_Color);
shader->addAttribute(kCCAttributeNameTexCoord, kCCVertexAttrib_TexCoords);
shader->link();
shader->updateUniforms();
_uniformOffset = glGetUniformLocation(shader->getProgram(), "texOffset");
_uniformURange = glGetUniformLocation(shader->getProgram(), "uRange");
_uniformVRange = glGetUniformLocation(shader->getProgram(), "vRange");
this->setShaderProgram(shader);
shader->release();
}
在load时，绑定shader中的uRange和vRange
3.渲染
void UVSprite::draw()
{
CC_PROFILER_START_CATEGORY(kCCProfilerCategorySprite, "CCSprite - draw");
CCAssert(!m_pobBatchNode, "If CCSprite is being rendered by CCSpriteBatchNode, CCSprite#draw SHOULD NOT be called");
getShaderProgram()->use();
getShaderProgram()->setUniformsForBuiltins();
ccGLBlendFunc( m_sBlendFunc.src, m_sBlendFunc.dst );
//bug fix with sprite frame
getShaderProgram()->setUniformLocationWith2f(_uniformURange, m_sQuad.bl.texCoords.u, m_sQuad.br.texCoords.u);
getShaderProgram()->setUniformLocationWith2f(_uniformVRange, m_sQuad.bl.texCoords.v, m_sQuad.tl.texCoords.v);
float offsetU = (m_sQuad.br.texCoords.u - m_sQuad.bl.texCoords.u) * _AutoScrollCountU;
float offsetV = (m_sQuad.tl.texCoords.v - m_sQuad.bl.texCoords.v) * _AutoScrollCountV;
getShaderProgram()->setUniformLocationWith2f(_uniformOffset, offsetU, offsetV);
//绑定纹理贴图
ccGLBindTexture2D( m_pobTexture->getName() );
ccGLEnableVertexAttribs( kCCVertexAttribFlag_PosColorTex );
#define kQuadSize sizeof(m_sQuad.bl)
#ifdef EMSCRIPTEN
long offset = 0;
setGLBufferData(&m_sQuad, 4 * kQuadSize, 0);
#else
long offset = (long)&m_sQuad;
#endif // EMSCRIPTEN
// 设置渲染坐标(x,y)
int diff = offsetof( ccV3F_C4B_T2F, vertices);
glVertexAttribPointer(kCCVertexAttrib_Position, 3, GL_FLOAT, GL_FALSE, kQuadSize, (void*) (offset + diff));
// 设置纹理坐标(u,v)
diff = offsetof( ccV3F_C4B_T2F, texCoords);
glVertexAttribPointer(kCCVertexAttrib_TexCoords, 2, GL_FLOAT, GL_FALSE, kQuadSize, (void*)(offset + diff));
// 设置顶点颜色
diff = offsetof( ccV3F_C4B_T2F, colors);
glVertexAttribPointer(kCCVertexAttrib_Color, 4, GL_UNSIGNED_BYTE, GL_TRUE, kQuadSize, (void*)(offset + diff));
//渲染矩形
glDrawArrays(GL_TRIANGLE_STRIP, 0, 4);
CHECK_GL_ERROR_DEBUG();
#if CC_SPRITE_DEBUG_DRAW == 1
// draw bounding box
CCPoint vertices[4]={
ccp(m_sQuad.tl.vertices.x,m_sQuad.tl.vertices.y),
ccp(m_sQuad.bl.vertices.x,m_sQuad.bl.vertices.y),
ccp(m_sQuad.br.vertices.x,m_sQuad.br.vertices.y),
ccp(m_sQuad.tr.vertices.x,m_sQuad.tr.vertices.y),
};
ccDrawPoly(vertices, 4, true);
#elif CC_SPRITE_DEBUG_DRAW == 2
// draw texture box
CCSize s = this->getTextureRect().size;
CCPoint offsetPix = this->getOffsetPosition();
CCPoint vertices[4] = {
ccp(offsetPix.x,offsetPix.y), ccp(offsetPix.x+s.width,offsetPix.y),
ccp(offsetPix.x+s.width,offsetPix.y+s.height), ccp(offsetPix.x,offsetPix.y+s.height)
};
ccDrawPoly(vertices, 4, true);
#endif // CC_SPRITE_DEBUG_DRAW
CC_INCREMENT_GL_DRAWS(1);
CC_PROFILER_STOP_CATEGORY(kCCProfilerCategorySprite, "CCSprite - draw");
}