I want to copy texture1 to texture2. The background is that I generate 15 empty texture id and bind them to GLES11Ext.GL_TEXTURE_EXTERNAL_OES, the following is my code:
int[] textures = new int[15];
GLES20.glGenTextures(15, textures, 0);
GlUtil.checkGlError("glGenTextures");
for(int i=0;i<15;i++)
GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, textures[i]);
then I always transfer camera preview to textures[0], I want copy the texture from textures[0] to textures[1] in order to keep the frame content of timestamp 1, and copy the texture from textures[0] to textures[2] in order to keep the frame content of timestamp 2... it looks like buffer some texture data in GPU and render some of that in the future. So I want to know is there anyway to do this? And can I just use textures[2]=textures[0] to copy texture data?
There isn't a very direct way to copy texture data in ES 2.0. The easiest way is probably using glCopyTexImage2D(). To use this, you have to create an FBO, and attach the source texture to it. Say if srcTexId is the id of the source texture, and dstTexId the id of the destination texture:
GLuint fboId = 0;
glGenFramebuffers(1, &fboId);
glBindFramebuffer(GL_FRAMEBUFFER, fboId);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, srcTexId, 0);
glBindTexture(GL_TEXTURE_2D, dstTexId);
glCopyTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, 0, 0, width, height, 0);
That being said, from your description, I don't believe that this is really what you should be doing, for the following reasons:
It sounds like you want to keep the 15 most recent camera images. To do this, you can simply track which of your 15 textures contains the most recent image, and treat the list of the 15 texture ids as a circular buffer.
Say initially you create your texture ids:
int[] textures = new int[15];
GLES20.glGenTextures(15, textures, 0);
int newestIdx = 0;
Then every time you receive a new frame, you write it to the next entry in your list of texture ids, wrapping around at 15:
newestIdx = (newestIdx + 1) % 15;
GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, textures[newestIdx]);
// Capture new frame into currently bound texture.
Then, every time you want to use the ith frame, with 0 referring to the most recent, 1 to the frame before that, etc, you bind it with:
GLES20.glBindTexture(GLES11Ext.GL_TEXTURE_EXTERNAL_OES, textures[(newestIdx + i) % 15]);
So the textures never get copied. You just keep track of which texture contains which frame, and access them accordingly.
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