使用和不使用CCRenderTexture的OpenGL ES绘图

Question

我知道我可以使用CCRenderTexture绘制OpenGL图形：

CCRenderTexture *rt = [CCRenderTexture renderTextureWithWidth:textureWidth height:textureHeight];
[rt beginWithClear:1, 1, 1, 1];

// OpenGL drawing like ......
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);
glBlendFunc(CC_BLEND_SRC, CC_BLEND_DST);
glDrawArrays(GL_TRIANGLE_STRIP, 0, (GLsizei)nVertices);

[rt end];

没有CCRenderTexture，似乎也没关系：

// OpenGL drawing like ......
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);
glBlendFunc(CC_BLEND_SRC, CC_BLEND_DST);
glDrawArrays(GL_TRIANGLE_STRIP, 0, (GLsizei)nVertices);

使用和不使用CCRenderTexture的OpenGL绘图有什么区别？