Delayed Texture load - over several frame - OpenGL

testApp.cpp

#include "testApp.h"


void testApp::setup(){

	ofSetFrameRate(60);
	ofSetVerticalSync(true);

	ofBackground(22);
	ofEnableAlphaBlending();
	ofDisableArbTex();

	img.loadImage("world4096.jpg");
	img2.loadImage("crap4096.jpg"); //this will be loaded into gpu over frames

	startLoading = false;
}

void testApp::update(){}


int loadedScanLinesSoFar = 0;

void testApp::draw(){

	int texW = img.getWidth();
	int texH = img.getHeight(); // == # scanLines
	int numLinesPerFrame = 1; //we can increase that to reduce overhead
	float maxTimeTakenPerFrame = 0.0003; //max seconds to spend loading tex data on a single frame

	ofTextureData texData = img.getTextureReference().texData;

	if(loadedScanLinesSoFar < texH && startLoading){
		////////////////////////////////////////////////////
		float startTime = ofGetElapsedTimef();
		glEnable(GL_TEXTURE_2D);
			glBindTexture( GL_TEXTURE_2D, texData.textureID );

			glEnable(GL_TEXTURE_2D);
			glBindTexture(GL_TEXTURE_2D, texData.textureID);

			float currentTime = 0;
			while (currentTime < maxTimeTakenPerFrame && loadedScanLinesSoFar < texH ) {
				unsigned char * data = img2.getPixels() + 3 * texW * loadedScanLinesSoFar; //assuming RGB here TODO!

				glTexSubImage2D(GL_TEXTURE_2D,
								0,							//level
								0,							//x offset
								loadedScanLinesSoFar,		//y offset
								texW,						//width
								numLinesPerFrame,			//height >> numLinesPerFrame line per iteration
								GL_RGB,						//format
								GL_UNSIGNED_BYTE,
								data
								);

				loadedScanLinesSoFar += numLinesPerFrame;
				currentTime = ofGetElapsedTimef() - startTime;
			}

		glDisable(GL_TEXTURE_2D);
		////////////////////////////////////////////////////
	}

	glEnable(GL_TEXTURE_2D);
	glBindTexture( GL_TEXTURE_2D, texData.textureID );

	//tex quad
	glBegin(GL_QUADS);
		glTexCoord2i(0,0);
		glVertex2i(0,0);
		glTexCoord2i(1,0);
		glVertex2i(ofGetWidth(),0);
		glTexCoord2i(1,1);
		glVertex2i(ofGetWidth(),ofGetHeight());
		glTexCoord2i(0,1);
		glVertex2i(0,ofGetHeight());
	glEnd();

	glDisable(GL_TEXTURE_2D);

	//clock
	ofPushMatrix();
	ofTranslate(50, 50);
	ofSetColor(0);
	ofCircle(0, 0, 50);
	ofRotate(ofGetFrameNum(), 0, 0, 1);
	ofSetColor(255);
	ofRect(0, 0, 50, 4);
	ofPopMatrix();

	if(startLoading){
		ofDrawBitmapStringHighlight("loaded " + ofToString(loadedScanLinesSoFar) + " lines so far (" + ofToString(texW) + ")", ofGetWidth() / 2, 20);
	}else{
		ofDrawBitmapStringHighlight("click anywhere to start delayed Texture Load", ofGetWidth() / 2,  20);
	}
	ofDrawBitmapStringHighlight( "fps: " + ofToString(ofGetFrameRate()), ofGetWidth() / 2,  40);


}


void testApp::keyPressed(int key){

}


void testApp::keyReleased(int key){

}


void testApp::mouseMoved(int x, int y){

}


void testApp::mouseDragged(int x, int y, int button){

}


void testApp::mousePressed(int x, int y, int button){
	startLoading = true;
}


void testApp::mouseReleased(int x, int y, int button){

}


void testApp::windowResized(int w, int h){

}


void testApp::gotMessage(ofMessage msg){

}


void testApp::dragEvent(ofDragInfo dragInfo){ 

}

testApp.h

#pragma once

#include "ofMain.h"


class testApp : public ofBaseApp{
	public:
		void setup();
		void update();
		void draw();
		
		void keyPressed(int key);
		void keyReleased(int key);
		void mouseMoved(int x, int y);
		void mouseDragged(int x, int y, int button);
		void mousePressed(int x, int y, int button);
		void mouseReleased(int x, int y, int button);
		void windowResized(int w, int h);
		void dragEvent(ofDragInfo dragInfo);
		void gotMessage(ofMessage msg);


		ofImage img;
		ofImage img2;

		bool startLoading;

};