Light Rays 0.5 - drawing into FBO

testapp.cpp

#include "testApp.h"

void testApp::setup(){
	ofBackground(33);
	ofSetVerticalSync(true);
	take_screenshot = false ;
	
	// create quad width size "s", centered
	float s = 1;
	float hs = s * 0.5;
	plane_data.addVertex(-hs,-hs,0);
	plane_data.addVertex(hs,-hs,0);
	plane_data.addVertex(hs,hs,0);
	plane_data.addVertex(-hs,hs,0);
	
	// add texture coordinates
	plane_data.addTexCoord(0,0);
	plane_data.addTexCoord(1,0);
	plane_data.addTexCoord(1,1);
	plane_data.addTexCoord(0,1);
		
	// create and bind VAO, which will remember:
	// - the next vbo we bind (and the state)
	// - the state of glEnableVertexAttribArray
	// - the specs of glVertexAttribPointer
	glGenVertexArraysAPPLE(1, &plane_vao); eglGetError();
	glBindVertexArrayAPPLE(plane_vao);
	
	// create shader
	// -------------
	shader.load("rays");
	shader.enable();
	shader.addUniform("projection_matrix");
	shader.addUniform("view_matrix");
	shader.addUniform("mode");
	shader.addUniform("texture");
	
	pos_attrib = glGetAttribLocation(shader.prog_id, "pos");

	
	// create VBO
	VertexP* vertex_data = plane_data.getVertexP();
	glGenBuffers(1, &plane_vbo); eglGetError();
	glBindBuffer(GL_ARRAY_BUFFER, plane_vbo); eglGetError();
	glBufferData(GL_ARRAY_BUFFER, sizeof(VertexP) * plane_data.size(), vertex_data, GL_STATIC_DRAW); eglGetError();
	
	// define how we use attributes and the buffer
	glBindBuffer(GL_ARRAY_BUFFER, plane_vbo);
	glEnableVertexAttribArray(pos_attrib); eglGetError(); // 
	glVertexAttribPointer(
		pos_attrib
		,3
		,GL_FLOAT
		,GL_FALSE
		,sizeof(VertexP)
		,(GLvoid*)offsetof(VertexP, pos)
	); eglGetError();

	
	// setup matrices
	projection.perspective(45.0f, 625.0f/469.0f, 0.1,100);
	model.identity();
	view.translate(0,0,-4);
	
	// setup FBO
	fbo.setup(625.0f, 469.0f);
	fbo.addTexture(0);
}

void testApp::draw(){
	// pass the projection matrix + view matrix to the shader.
	shader.enable();
	shader.uniformMat4fv("projection_matrix", projection.getPtr());
	shader.uniformMat4fv("view_matrix", view.getPtr());
	
	// draw the scene into a texture
	fbo.begin();	
		shader.uniform1i("mode", 1); // draw w/o textures
		glBindVertexArrayAPPLE(plane_vao);
		glDrawArrays(GL_QUADS, 0, 4);	
	fbo.end();
	
	
	if(take_screenshot) {
		ofSaveScreen("light_rays_"+ofToString(ofGetHours()) +"_" +ofToString(ofGetMinutes()) +"_" +ofToString(ofGetSeconds()) +".png");
		take_screenshot = false;
	}
}

void testApp::keyPressed(int key){
	if(key == ' ') {
		take_screenshot = !take_screenshot;
	}
}

testapp.h

#pragma once

#include "ofMain.h"
#include "Roxlu.h"
using namespace roxlu;

class testApp : public ofBaseApp{

	public:
		void setup();
		void update();
		void draw();
		void keyPressed  (int key);
		
		bool take_screenshot;
		Mat4 projection;
		Mat4 view;	
		Mat4 model;
		VertexData plane_data;
		Shader shader;
		FBO fbo;
		GLuint plane_vbo;
		GLuint plane_vao;
		GLint pos_attrib;
		

		// not used in example
		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);
};

result is black because we're only drawing the scene into a fbo