ofPBO.cpp

/*
 * ofPBO.cpp
 *
 *  Created on: 08/04/2012
 *      Author: arturo
 *  Revised on: 2016-08-27
 *     Reviser: ofIan, Ian Byun
 *     updated to match deletion and renaming of ofTextureData members
 */

#include "ofPBO.h"

ofPBO::ofPBO() {
	// TODO Auto-generated constructor stub

}

ofPBO::~ofPBO() {
	if(!pboIds.empty()){
		glDeleteBuffersARB(pboIds.size(), &pboIds[0]);
	}
}

void ofPBO::allocate(ofTexture & tex, int numPBOs) {
	pboIds.resize(numPBOs);
    glGenBuffersARB(numPBOs, &pboIds[0]);
    int numChannels=1;
    switch(tex.getTextureData().glInternalFormat) {
    case GL_LUMINANCE:
    	numChannels = 1;
    	break;
	case GL_RGB: case GL_RGB8:
    	numChannels = 3;
    	break;
	case GL_RGBA: case GL_RGBA8:
    	numChannels = 4;
    	break;
    }
    dataSize = tex.getWidth()*tex.getHeight()*numChannels;
    for(int i=0; i<(int)pboIds.size(); i++){
		glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, pboIds[i]);
		glBufferDataARB(GL_PIXEL_UNPACK_BUFFER_ARB, dataSize, 0, GL_STREAM_DRAW_ARB);
    }
    glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, 0);

    texture = tex;
	
	glInternalFormat = tex.getTextureData().glInternalFormat;			//GL_RGB8
	glFormat = ofGetGLFormatFromInternal(glInternalFormat);		//GL_RGB
	glType = ofGetGlTypeFromInternal(glInternalFormat);					//GL_UNSIGNED_BYTE

	ofLogNotice() << "glInternalFormat: " << ofGetGlInternalFormatName(glInternalFormat);
	ofLogNotice() << "glFormat: " << ofGetGlInternalFormatName(glFormat);
	ofLogNotice() << "glType: " << (glType == GL_UNSIGNED_BYTE? "GL_UNSIGNED_BYTE" : ofToString(glType)) << endl;
}

void ofPBO::updateData(const ofPixels & pixels) {
	if(pboIds.empty()){
		ofLogError() << "pbo not allocated";
		return;
	}

	//this is from http://www.songho.ca/opengl/gl_pbo.html

	// "index" is used to copy pixels from a PBO to a texture object
	// "nextIndex" is used to update pixels in the other PBO
    index = (index + 1) % pboIds.size(); // 오버플로우를 감안한 ++index
    int nextIndex = (index + 1) % pboIds.size(); 

	// bind PBO to update pixel values
	glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, pboIds[nextIndex]);

	// map the buffer object into client's memory
	// Note that glMapBufferARB() causes sync issue.
	// If GPU is working with this buffer, glMapBufferARB() will wait(stall)
	// for GPU to finish its job. To avoid waiting (stall), you can call
	// first glBufferDataARB() with NULL pointer before glMapBufferARB().
	// If you do that, the previous data in PBO will be discarded and
	// glMapBufferARB() returns a new allocated pointer immediately
	// even if GPU is still working with the previous data.
	glBufferDataARB(GL_PIXEL_UNPACK_BUFFER_ARB, dataSize, 0, GL_STREAM_DRAW_ARB);
	GLubyte* ptr = (GLubyte*)glMapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, GL_WRITE_ONLY_ARB);
	if(ptr) {
		// update data directly on the mapped buffer
		memcpy(ptr, pixels.getPixels(), dataSize);
		glUnmapBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB); // release pointer to mapping buffer
	}

    // it is good idea to release PBOs with ID 0 after use.
    // Once bound with 0, all pixel operations behave normal ways.
    glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
}

void ofPBO::updateTexture() {
	// bind the texture and PBO
	texture.bind();
	glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, pboIds[index]);
	//http://stackoverflow.com/questions/2405734/difference-between-gltexsubimage-and-glteximage-function-in-opengl
	//https://www.opengl.org/wiki/Common_Mistakes#Texture_upload_and_pixel_reads
	//https://www.opengl.org/sdk/docs/man/html/glTexSubImage2D.xhtml
	glTexSubImage2D(texture.getTextureData().textureTarget, 0, 0, 0, texture.getWidth(), texture.getHeight(), glFormat, glType, 0);
    texture.unbind();
    // it is good idea to release PBOs with ID 0 after use.
    // Once bound with 0, all pixel operations behave normal ways.
    glBindBufferARB(GL_PIXEL_UNPACK_BUFFER_ARB, 0);
}