Cocos2dx CCRenderTexture - OpenGL ES2未渲染

Question

我正在尝试在Cocos2dx 2、OpenGL ES2中向纹理添加渐变。 但OpenGL内容无法被渲染。

这段代码基于以下教程链接： 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。

- Paramesh

Answer 1

看起来我们需要使用ccVertex2F而不是CCPoint来表示顶点。

此外，混合函数在绘制渐变时并不是必需的。

以下是更新后的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);

- Paramesh

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谢谢！我可以问一下你最终是怎么找到解决方案的吗？ - Zaky German

Answer 2

我不太确定它是如何工作的，但如果你只是想要一个带有渐变颜色的东西，你可以尝试或查看CCLayerGradient的源代码， 这里是链接http://www.cocos2d-x.org/reference/native-cpp/d9/d19/classcocos2d_1_1_c_c_layer_gradient.html

- m.ding

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谢谢，但我想了解为什么代码无法工作。因为教程中还有一些要在OpenGL中绘制的额外内容，如果这个初始步骤不能正常运行，我就无法继续进行了。 - Paramesh