I have loads of shaders and about 10 textures for GPGPU. I use color attachments. After doing all the calculations I want to get the data back from the textures. The below is good as long as the texture is still attached the color attachment.

	glBindTexture(iTextureType,texId);
	glReadBuffer(GL_COLOR_ATTACHMENT0_EXT);
	glReadPixels(0, 0, itexSizeW, itexSizeH, GL_RGBA, GL_FLOAT, textureData);

But how can i get the texture data if the color attachments have been cleared ? Have I lost the data for good ? basically i want to simply do:

	glBindTexture(iTextureType,texId);
	glReadPixels(0, 0, itexSizeW, itexSizeH, GL_RGBA, GL_FLOAT, textureData);

cheers