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我正在尝试为 Cocos2dx 2、OpenGL ES2 中的纹理添加渐变。但是 OpenGL 内容没有被渲染。

此代码基于教程链接： http ://www.raywenderlich.com/3857/how-to-create-dynamic-textures-with-ccrendertexture

CCRenderTexture *rt = CCRenderTexture::create((int)textureSize, (int)textureSize);
rt->beginWithClear(bgColor.r, bgColor.g, bgColor.b, bgColor.a);

float gradientAlpha = 0.5;
CCPoint vertices[4];
ccColor4F colors[4];
int nVertices = 0;

vertices[nVertices] = CCPointMake(0, 0);
colors[nVertices++] = ccc4f(0, 0, 0, 0);
vertices[nVertices] = CCPointMake(textureSize, 0);
colors[nVertices++] = ccc4f(0, 0, 0, 0);
vertices[nVertices] = CCPointMake(0, textureSize);
colors[nVertices++] = ccc4f(0, 0, 0, gradientAlpha);
vertices[nVertices] = CCPointMake(textureSize, textureSize);
colors[nVertices++] = ccc4f(0, 0, 0, gradientAlpha);

// Set the shader program for OpenGL
setShaderProgram(CCShaderCache::sharedShaderCache()->programForKey(kCCShader_PositionColor));
CC_NODE_DRAW_SETUP();

glVertexAttribPointer(kCCVertexAttrib_Position, 2, GL_FLOAT, GL_FALSE, 0, vertices);
glVertexAttribPointer(kCCVertexAttrib_Color, 4, GL_FLOAT, GL_FALSE, 0, colors);
ccGLBlendFunc(CC_BLEND_SRC, CC_BLEND_DST);
glDrawArrays(GL_TRIANGLE_STRIP, 0, (GLsizei)nVertices);

CCSprite* noise = CCSprite::create("Noise.png");
ccBlendFunc blendFunc;
blendFunc.src = GL_DST_COLOR;
blendFunc.dst = GL_ZERO;
noise->setBlendFunc(blendFunc);
noise->setPosition(ccp(textureSize / 2, textureSize / 2));
noise->visit();

rt->end();
return CCSprite::createWithTexture(rt->getSprite()->getTexture());

如果我做错了什么，请告诉我。谢谢你。

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2 回答 2

4

看起来我们必须使用 ccVertex2F 而不是 CCPoint 作为顶点。

此外，混合函数对于绘制渐变没有明确要求。

这是更新的 C++ 代码： 

float gradientAlpha = 0.5;
ccVertex2F vertices[4];
ccColor4F colors[4];
int nVertices = 0;

vertices[nVertices] = vertex2(0, 0);
colors[nVertices++] = ccc4f(0, 0, 0, 0);
vertices[nVertices] = vertex2(textureSize, 0);
colors[nVertices++] = ccc4f(0, 0, 0, 0);
vertices[nVertices] = vertex2(0, textureSize);
colors[nVertices++] = ccc4f(0, 0, 0, gradientAlpha);
vertices[nVertices] = vertex2(textureSize, textureSize);
colors[nVertices++] = ccc4f(0, 0, 0, gradientAlpha);

// Set the shader program for OpenGL
setShaderProgram(CCShaderCache::sharedShaderCache()->programForKey(kCCShader_PositionColor));
CC_NODE_DRAW_SETUP();

ccGLEnableVertexAttribs(kCCVertexAttribFlag_Position  | kCCVertexAttribFlag_Color);

glVertexAttribPointer(kCCVertexAttrib_Position, 2, GL_FLOAT, GL_FALSE, 0, vertices);
glVertexAttribPointer(kCCVertexAttrib_Color, 4, GL_FLOAT, GL_FALSE, 0, colors);

glDrawArrays(GL_TRIANGLE_STRIP, 0, (GLsizei)nVertices);
于 2012-11-14T20:02:12.487 回答
1

我不太确定它是如何工作的，但如果你只想要渐变颜色的东西，你可以尝试或检查 CCLayerGradient 的源代码，这里是链接http://www.cocos2d-x.org/reference/本机-cpp/d9/d19/classcocos2d_1_1_c_c_layer_gradient.html

于 2012-11-07T04:32:25.467 回答