• Announcements

    • khawk

      Download the Game Design and Indie Game Marketing Freebook   07/19/17

      GameDev.net and CRC Press have teamed up to bring a free ebook of content curated from top titles published by CRC Press. The freebook, Practices of Game Design & Indie Game Marketing, includes chapters from The Art of Game Design: A Book of Lenses, A Practical Guide to Indie Game Marketing, and An Architectural Approach to Level Design. The GameDev.net FreeBook is relevant to game designers, developers, and those interested in learning more about the challenges in game development. We know game development can be a tough discipline and business, so we picked several chapters from CRC Press titles that we thought would be of interest to you, the GameDev.net audience, in your journey to design, develop, and market your next game. The free ebook is available through CRC Press by clicking here. The Curated Books The Art of Game Design: A Book of Lenses, Second Edition, by Jesse Schell Presents 100+ sets of questions, or different lenses, for viewing a game’s design, encompassing diverse fields such as psychology, architecture, music, film, software engineering, theme park design, mathematics, anthropology, and more. Written by one of the world's top game designers, this book describes the deepest and most fundamental principles of game design, demonstrating how tactics used in board, card, and athletic games also work in video games. It provides practical instruction on creating world-class games that will be played again and again. View it here. A Practical Guide to Indie Game Marketing, by Joel Dreskin Marketing is an essential but too frequently overlooked or minimized component of the release plan for indie games. A Practical Guide to Indie Game Marketing provides you with the tools needed to build visibility and sell your indie games. With special focus on those developers with small budgets and limited staff and resources, this book is packed with tangible recommendations and techniques that you can put to use immediately. As a seasoned professional of the indie game arena, author Joel Dreskin gives you insight into practical, real-world experiences of marketing numerous successful games and also provides stories of the failures. View it here. An Architectural Approach to Level Design This is one of the first books to integrate architectural and spatial design theory with the field of level design. The book presents architectural techniques and theories for level designers to use in their own work. It connects architecture and level design in different ways that address the practical elements of how designers construct space and the experiential elements of how and why humans interact with this space. Throughout the text, readers learn skills for spatial layout, evoking emotion through gamespaces, and creating better levels through architectural theory. View it here. Learn more and download the ebook by clicking here. Did you know? GameDev.net and CRC Press also recently teamed up to bring GDNet+ Members up to a 20% discount on all CRC Press books. Learn more about this and other benefits here.
Sign in to follow this  
Followers 0
VCAlfox

OpenGL
SOLVED: Render a vector to screen in opengl

8 posts in this topic

Hello,

I have this simple code (just a green cube in scene):

// Include standard headers
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <vector>
#include <windows.h>
// Include GLEW
#include <glew.h>
 
// Include GLFW
#include <glfw3.h>
GLFWwindow* window;
 
// Include GLM
#include <glm.hpp>
#include <gtc/matrix_transform.hpp>
using namespace glm;
 
#include "shader.hpp"
 
int main( void )
{
	// Initialise GLFW
	if( !glfwInit() )
	{
		fprintf( stderr, "Failed to initialize GLFW\n" );
		return -1;
	}
 
	glfwWindowHint(GLFW_SAMPLES, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
 
	// Open a window and create its OpenGL context
	window = glfwCreateWindow( 1024, 768, "Cube", NULL, NULL);
	if( window == NULL ){
		fprintf( stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.\n" );
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);
 
	// Initialize GLEW
	glewExperimental = true; // Needed for core profile
	if (glewInit() != GLEW_OK) {
		fprintf(stderr, "Failed to initialize GLEW\n");
		return -1;
	}
 
	// Ensure we can capture the escape key being pressed below
	glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);
 
	// Dark blue background
	glClearColor(0.0f, 0.0f, 0.4f, 0.0f);
 
	// Enable depth test
	glEnable(GL_DEPTH_TEST);
	// Accept fragment if it closer to the camera than the former one
	glDepthFunc(GL_LESS); 
 
	GLuint VertexArrayID;
	glGenVertexArrays(1, &VertexArrayID);
	glBindVertexArray(VertexArrayID);
 
	// Create and compile our GLSL program from the shaders
	GLuint programID = LoadShaders( "TransformVertexShader.vertexshader", "ColorFragmentShader.fragmentshader" );
 
	// Get a handle for our "MVP" uniform
	GLuint MatrixID = glGetUniformLocation(programID, "MVP");
 
	// Projection matrix : 45° Field of View, 4:3 ratio, display range : 0.1 unit <-> 100 units
	glm::mat4 Projection = glm::perspective(45.0f, 4.0f / 3.0f, 0.1f, 100.0f);
	// Camera matrix
	glm::mat4 View       = glm::lookAt(
								glm::vec3(4,3,-3), // Camera is at (4,3,-3), in World Space
								glm::vec3(0,0,0), // and looks at the origin
								glm::vec3(0,1,0)  // Head is up (set to 0,-1,0 to look upside-down)
						   );
	// Model matrix : an identity matrix (model will be at the origin)
	glm::mat4 Model      = glm::mat4(1.0f);
	// Our ModelViewProjection : multiplication of our 3 matrices
	glm::mat4 MVP        = Projection * View * Model; // Remember, matrix multiplication is the other way around
 
	// Our vertices. Tree consecutive floats give a 3D vertex; Three consecutive vertices give a triangle.
	// A cube has 6 faces with 2 triangles each, so this makes 6*2=12 triangles, and 12*3 vertices
	static const GLfloat g_vertex_buffer_data[] = { 
		-1.0f,-1.0f,-1.0f,
		-1.0f,-1.0f, 1.0f,
		-1.0f, 1.0f, 1.0f,
		 1.0f, 1.0f,-1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f, 1.0f,
		-1.0f,-1.0f,-1.0f,
		 1.0f,-1.0f,-1.0f,
		 1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f,-1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f, 1.0f, 1.0f,
		-1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f, 1.0f,
		-1.0f,-1.0f, 1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f, 1.0f, 1.0f,
		-1.0f,-1.0f, 1.0f,
		 1.0f,-1.0f, 1.0f,
		 1.0f, 1.0f, 1.0f,
		 1.0f,-1.0f,-1.0f,
		 1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f,-1.0f,
		 1.0f, 1.0f, 1.0f,
		 1.0f,-1.0f, 1.0f,
		 1.0f, 1.0f, 1.0f,
		 1.0f, 1.0f,-1.0f,
		-1.0f, 1.0f,-1.0f,
		 1.0f, 1.0f, 1.0f,
		-1.0f, 1.0f,-1.0f,
		-1.0f, 1.0f, 1.0f,
		 1.0f, 1.0f, 1.0f,
		-1.0f, 1.0f, 1.0f,
		 1.0f,-1.0f, 1.0f
	};
 
	// One color for each vertex. They were generated randomly.
	static const GLfloat g_color_buffer_data[] = { 
		0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f
	};
 
	GLuint vertexbuffer;
	glGenBuffers(1, &vertexbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW);
 
	GLuint colorbuffer;
	glGenBuffers(1, &colorbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(g_color_buffer_data), g_color_buffer_data, GL_STATIC_DRAW);
 
	do{
              std::vector<GLfloat> pixel(1024*768*3);
              glReadPixels(0, 0, 1024, 768, GL_RGB, GL_FLOAT, &pixel[0]);
              std::cout << "R G B: " << pixel[0]<< " "<<pixel[1]<< " "<<pixel[2] << "\n"; //not really needed
       
		// Clear the screen
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
 
		// Use our shader
		glUseProgram(programID);
 
		// Send our transformation to the currently bound shader, 
		// in the "MVP" uniform
		glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);
 
		// 1rst attribute buffer : vertices
		glEnableVertexAttribArray(0);
		glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
		glVertexAttribPointer(
			0,                  // attribute. No particular reason for 0, but must match the layout in the shader.
			3,                  // size
			GL_FLOAT,           // type
			GL_FALSE,           // normalized?
			0,                  // stride
			(void*)0            // array buffer offset
		);
 
		// 2nd attribute buffer : colors
		glEnableVertexAttribArray(1);
		glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
		glVertexAttribPointer(
			1,                                // attribute. No particular reason for 1, but must match the layout in the shader.
			3,                                // size
			GL_FLOAT,                         // type
			GL_FALSE,                         // normalized?
			0,                                // stride
			(void*)0                          // array buffer offset
		);
 
		// Draw the triangle !
		glDrawArrays(GL_TRIANGLES, 0, 12*3); // 12*3 indices starting at 0 -> 12 triangles
 
		glDisableVertexAttribArray(0);
		glDisableVertexAttribArray(1);
 
		// Swap buffers
		glfwSwapBuffers(window);
		glfwPollEvents();
 
	} // Check if the ESC key was pressed or the window was closed
	while( glfwGetKey(window, GLFW_KEY_ESCAPE ) != GLFW_PRESS &&
		   glfwWindowShouldClose(window) == 0 );
 
	// Cleanup VBO and shader
	glDeleteBuffers(1, &vertexbuffer);
	glDeleteBuffers(1, &colorbuffer);
	glDeleteProgram(programID);
	glDeleteVertexArrays(1, &VertexArrayID);
 
	// Close OpenGL window and terminate GLFW
	glfwTerminate();
 
	return 0;
}

As you can see I have this lines:

std::vector<GLfloat> pixel(1024*768*3);
glReadPixels(0, 0, 1024, 200, GL_RGB, GL_FLOAT, &pixel[0]);

Now, how Can I pass the pixel vector to Opengl for render him and not the standard way?

I need this because I want to manipulate in same way the pixel vector and than pass him to opengl for render.

But I don't know how to do that.

 

Thanks

Edited by Alfox
0

Share this post


Link to post
Share on other sites

You know that glReadPixels just reads what's on the screen already, so what are you actually trying to do? Copy the screen for re-rendering at a later time?

 

What are you considering "the standard way"?

 

Modern, you would populate the texture with the pixel data, and render the texture with a shader.. But then again you also wouldn't be using glReadPixels.

 

So - maybe glDrawPixels?

0

Share this post


Link to post
Share on other sites

Hi thanks for reply,

I used glReadPixels because searching on google this function was the result. But if there is another way I can delete this function

 

 

you would populate the texture with the pixel data, and render the texture with a shader

 

yes, I want populate the texture with the pixel data, precisely I want

1. collect the pixels color information in a structure (like glReadPixels does)

2. modify same pixels color (for instance in my previous example, modify the green pixels to become blue)

3. render the pixels data modified.

 

 

What are you considering "the standard way"?

 

render to screen with the vertex buffer and color buffer.

 

I tried also to follow a tutorial on how render to texture, but also in this way I don't know how to modify the code for manipulate the pixels before render them on screen.

0

Share this post


Link to post
Share on other sites

There is glDrawPixels

 

Keep in mind this function is deprecated and I wouldn't do any image processing using glReadPixels with glDrawPixels in any production code.

 

 

You should use a shader program to process the render output. To do that, you render your scene to an offscreen framebuffer bound to a texture. You then use that texture as the input to drawing a quad over the entire screen.

 

Here is an example of how to do this.

Render to Texture

1

Share this post


Link to post
Share on other sites

Hello

yes I read about glDrawPixels and I don't want to use it, because as you said is deprecated.

 

I already read that tutorial, and tried, but how can I access to pixels after saved in framebuffer but before rendered on the quad?

for instance:

- save all in the framebuffer

- access to saved pixels and modify samething

- render the modified framebuffer to the quad

0

Share this post


Link to post
Share on other sites

If you are creating a framebuffer object you will most likly attach a texture (previously generated with glGenTextures ()...) as color rendertarget using the glFramebufferTexture() function.

 

I dont know if I understood you right but I guess you want to do something like this:

1 Bind the fbo for offscreen rendering

2 Render anything you like

3 Unbind the fbo

4 Retrieve texture data from your rendered image into main memory (you can do that using glGetTexImage() with the texture you have attached as colortarget to your fbo)

5 Modify the texture data in main memory and update the texture on you graphics card (with glTexSubImage2D ())

6 Render the modified texture in a fullscreen quad to your window backbuffer

 

 

This will work, although I highly recommend not to do this, and do what ever you want to modify in your texture on the gpu.

If it is just a pixel operation you want to do, then you can do the same as I described above but omit the steps 4 and 5 and do all modifications in the fragment shader stage.

 

2

Share this post


Link to post
Share on other sites

Hello!

yes this is what I want to do

I created this (whit the help of the tutorial linked above by HappyCoder )

// Include standard headers
#include <stdio.h>
#include <stdlib.h>
#include <iostream>
#include <vector>
#include <windows.h>
// Include GLEW
#include <glew.h>

// Include GLFW
#include <glfw3.h>
GLFWwindow* window;

// Include GLM
#include <glm.hpp>
#include <gtc/matrix_transform.hpp>
using namespace glm;

#include "shader.hpp"

int main( void )
{
	// Initialise GLFW
	if( !glfwInit() )
	{
		fprintf( stderr, "Failed to initialize GLFW\n" );
		return -1;
	}

	glfwWindowHint(GLFW_SAMPLES, 4);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);

	// Open a window and create its OpenGL context
	window = glfwCreateWindow( 1024, 768, "Cube", NULL, NULL);
	if( window == NULL ){
		fprintf( stderr, "Failed to open GLFW window. If you have an Intel GPU, they are not 3.3 compatible. Try the 2.1 version of the tutorials.\n" );
		glfwTerminate();
		return -1;
	}
	glfwMakeContextCurrent(window);

	// Initialize GLEW
	glewExperimental = true; // Needed for core profile
	if (glewInit() != GLEW_OK) {
		fprintf(stderr, "Failed to initialize GLEW\n");
		return -1;
	}

	// Ensure we can capture the escape key being pressed below
	glfwSetInputMode(window, GLFW_STICKY_KEYS, GL_TRUE);

	// Dark blue background
	glClearColor(0.0f, 0.0f, 0.4f, 0.0f);

	// Enable depth test
	glEnable(GL_DEPTH_TEST);
	// Accept fragment if it closer to the camera than the former one
	//glDepthFunc(GL_LESS); 

	GLuint VertexArrayID;
	glGenVertexArrays(1, &VertexArrayID);
	glBindVertexArray(VertexArrayID);

	// Create and compile our GLSL program from the shaders
	GLuint programID = LoadShaders( "TransformVertexShader.vertexshader", "ColorFragmentShader.fragmentshader" );

	// Get a handle for our "MVP" uniform
	GLuint MatrixID = glGetUniformLocation(programID, "MVP");

	// Projection matrix : 45° Field of View, 4:3 ratio, display range : 0.1 unit <-> 100 units
	glm::mat4 Projection = glm::perspective(45.0f, 4.0f / 3.0f, 0.1f, 100.0f);
	// Camera matrix
	glm::mat4 View       = glm::lookAt(
								glm::vec3(4,3,-3), // Camera is at (4,3,-3), in World Space
								glm::vec3(0,0,0), // and looks at the origin
								glm::vec3(0,1,0)  // Head is up (set to 0,-1,0 to look upside-down)
						   );
	// Model matrix : an identity matrix (model will be at the origin)
	glm::mat4 Model      = glm::mat4(1.0f);
	// Our ModelViewProjection : multiplication of our 3 matrices
	glm::mat4 MVP        = Projection * View * Model; // Remember, matrix multiplication is the other way around

	// Our vertices. Tree consecutive floats give a 3D vertex; Three consecutive vertices give a triangle.
	// A cube has 6 faces with 2 triangles each, so this makes 6*2=12 triangles, and 12*3 vertices
	static const GLfloat g_vertex_buffer_data[] = { 
		-1.0f,-1.0f,-1.0f,
		-1.0f,-1.0f, 1.0f,
		-1.0f, 1.0f, 1.0f,
		 1.0f, 1.0f,-1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f, 1.0f,
		-1.0f,-1.0f,-1.0f,
		 1.0f,-1.0f,-1.0f,
		 1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f,-1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f, 1.0f, 1.0f,
		-1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f, 1.0f,
		-1.0f,-1.0f, 1.0f,
		-1.0f,-1.0f,-1.0f,
		-1.0f, 1.0f, 1.0f,
		-1.0f,-1.0f, 1.0f,
		 1.0f,-1.0f, 1.0f,
		 1.0f, 1.0f, 1.0f,
		 1.0f,-1.0f,-1.0f,
		 1.0f, 1.0f,-1.0f,
		 1.0f,-1.0f,-1.0f,
		 1.0f, 1.0f, 1.0f,
		 1.0f,-1.0f, 1.0f,
		 1.0f, 1.0f, 1.0f,
		 1.0f, 1.0f,-1.0f,
		-1.0f, 1.0f,-1.0f,
		 1.0f, 1.0f, 1.0f,
		-1.0f, 1.0f,-1.0f,
		-1.0f, 1.0f, 1.0f,
		 1.0f, 1.0f, 1.0f,
		-1.0f, 1.0f, 1.0f,
		 1.0f,-1.0f, 1.0f
	};

	// One color for each vertex. They were generated randomly.
	static const GLfloat g_color_buffer_data[] = { 
		0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f,
				0.583f,  0.771f,  0.014f
	};

	GLuint vertexbuffer;
	glGenBuffers(1, &vertexbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(g_vertex_buffer_data), g_vertex_buffer_data, GL_STATIC_DRAW);

	GLuint colorbuffer;
	glGenBuffers(1, &colorbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(g_color_buffer_data), g_color_buffer_data, GL_STATIC_DRAW);

	glUseProgram(programID);


		// ---------------------------------------------
	// Render to Texture - specific code begins here
	// ---------------------------------------------

	// The framebuffer, which regroups 0, 1, or more textures, and 0 or 1 depth buffer.
	GLuint FramebufferName = 0;
	glGenFramebuffers(1, &FramebufferName);
	glBindFramebuffer(GL_FRAMEBUFFER, FramebufferName);

	// The texture we're going to render to
	GLuint renderedTexture;
	glGenTextures(1, &renderedTexture);
	
	// "Bind" the newly created texture : all future texture functions will modify this texture
	glBindTexture(GL_TEXTURE_2D, renderedTexture);

	// Give an empty image to OpenGL ( the last "0" means "empty" )
	glTexImage2D(GL_TEXTURE_2D, 0,GL_RGB, 1024, 768, 0,GL_RGBA, GL_UNSIGNED_BYTE, 0);

	// Poor filtering
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST); 
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

	// The depth buffer
	GLuint depthrenderbuffer;
	glGenRenderbuffers(1, &depthrenderbuffer);
	glBindRenderbuffer(GL_RENDERBUFFER, depthrenderbuffer);
	glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, 1024, 768);
	glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthrenderbuffer);

	//----------------------------

	// Set "renderedTexture" as our colour attachement #0
	glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, renderedTexture, 0);

	// Set the list of draw buffers.
	GLenum DrawBuffers[1] = {GL_COLOR_ATTACHMENT0};
	glDrawBuffers(1, DrawBuffers); // "1" is the size of DrawBuffers

	// Always check that our framebuffer is ok
	if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
	{
		printf("\nFrameBuffer Error\n");
		return false;
	}

	
	// The fullscreen quad's FBO
	static const GLfloat g_quad_vertex_buffer_data[] = { 
		-1.0f, -1.0f, 0.0f,
		 1.0f, -1.0f, 0.0f,
		-1.0f,  1.0f, 0.0f,
		-1.0f,  1.0f, 0.0f,
		 1.0f, -1.0f, 0.0f,
		 1.0f,  1.0f, 0.0f,
	};

	GLuint quad_vertexbuffer;
	glGenBuffers(1, &quad_vertexbuffer);
	glBindBuffer(GL_ARRAY_BUFFER, quad_vertexbuffer);
	glBufferData(GL_ARRAY_BUFFER, sizeof(g_quad_vertex_buffer_data), g_quad_vertex_buffer_data, GL_STATIC_DRAW);

	// Create and compile our GLSL program from the shaders
	GLuint quad_programID = LoadShaders( "Passthrough.vertexshader", "WobblyTexture.fragmentshader" );
	GLuint texID = glGetUniformLocation(quad_programID, "renderedTexture");


	do{

		//std::vector<GLfloat> pixel(1024*768*3); 
		//glReadPixels(0, 0, 1024, 768, GL_RGB, GL_FLOAT, &pixel[0]);
	

		// Render to our framebuffer
		glBindFramebuffer(GL_FRAMEBUFFER, FramebufferName);
		glViewport(0,0,1024,768); // Render on the whole framebuffer, complete from the lower left corner to the upper right

		// Clear the screen
		glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

		// Use our shader
		glUseProgram(programID);

		// Send our transformation to the currently bound shader, 
		// in the "MVP" uniform
		glUniformMatrix4fv(MatrixID, 1, GL_FALSE, &MVP[0][0]);

		// 1rst attribute buffer : vertices
		glEnableVertexAttribArray(0);
		glBindBuffer(GL_ARRAY_BUFFER, vertexbuffer);
		glVertexAttribPointer(
			0,                  // attribute. No particular reason for 0, but must match the layout in the shader.
			3,                  // size
			GL_FLOAT,           // type
			GL_FALSE,           // normalized?
			0,                  // stride
			(void*)0            // array buffer offset
		);

		// 2nd attribute buffer : colors
		glEnableVertexAttribArray(1);
		glBindBuffer(GL_ARRAY_BUFFER, colorbuffer);
		glVertexAttribPointer(
			1,                                // attribute. No particular reason for 1, but must match the layout in the shader.
			3,                                // size
			GL_FLOAT,                         // type
			GL_FALSE,                         // normalized?
			0,                                // stride
			(void*)0                          // array buffer offset
		);

		// Draw the triangle !
		glDrawArrays(GL_TRIANGLES, 0, 12*3); // 12*3 indices starting at 0 -> 12 triangles

		glDisableVertexAttribArray(0);
		glDisableVertexAttribArray(1);

		

		// Render to the screen
		glBindFramebuffer(GL_FRAMEBUFFER, 0);
		glViewport(0,0,1024,768); // Render on the whole framebuffer, complete from the lower left corner to the upper right

		// Clear the screen
		glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

		// Use our shader
		glUseProgram(quad_programID);

		
		// Bind our texture in Texture Unit 0
		glActiveTexture(GL_TEXTURE0);
		glBindTexture(GL_TEXTURE_2D, renderedTexture);
		// Set our "renderedTexture" sampler to user Texture Unit 0
		glUniform1i(texID, 0);

		// 1rst attribute buffer : vertices
		glEnableVertexAttribArray(0);
		glBindBuffer(GL_ARRAY_BUFFER, quad_vertexbuffer);
		glVertexAttribPointer(
			0,                  // attribute 0. No particular reason for 0, but must match the layout in the shader.
			3,                  // size
			GL_FLOAT,           // type
			GL_FALSE,           // normalized?
			0,                  // stride
			(void*)0            // array buffer offset
		);

		
		// Draw the triangles !
		glDrawArrays(GL_TRIANGLES, 0, 6); // 2*3 indices starting at 0 -> 2 triangles

		glDisableVertexAttribArray(0);

		

		// Swap buffers
		glfwSwapBuffers(window);
		glfwPollEvents();

	} // Check if the ESC key was pressed or the window was closed
	while( glfwGetKey(window, GLFW_KEY_ESCAPE ) != GLFW_PRESS &&
		   glfwWindowShouldClose(window) == 0 );

		// Cleanup VBO and shader
	glDeleteBuffers(1, &vertexbuffer);
	glDeleteBuffers(1, &colorbuffer);
	glDeleteProgram(programID);


	glDeleteFramebuffers(1, &FramebufferName);
	glDeleteTextures(1, &renderedTexture);
	glDeleteRenderbuffers(1, &depthrenderbuffer);
	glDeleteBuffers(1, &quad_vertexbuffer);
	glDeleteVertexArrays(1, &VertexArrayID);

	// Close OpenGL window and terminate GLFW
	glfwTerminate();

	return 0;
}


So now I render the cube in the framebuffer than, render the framebuffer on the quad.

 

As you suggest I have to retrieve data after call this:

		// Draw the triangle !
		glDrawArrays(GL_TRIANGLES, 0, 12*3); // 12*3 indices starting at 0 -> 12 triangles

		glDisableVertexAttribArray(0);
		glDisableVertexAttribArray(1);

with glGetTexImage()

modify the texture, than update the modified texture with glTexSubImage2D ()

 

and than continue with:

		// Render to the screen
		glBindFramebuffer(GL_FRAMEBUFFER, 0);
		glViewport(0,0,1024,768); // Render on the whole framebuffer, complete from the lower left corner to the upper right

		// Clear the screen
		glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

		// Use our shader
		glUseProgram(quad_programID);

		
		// Bind our texture in Texture Unit 0
		glActiveTexture(GL_TEXTURE0);
		glBindTexture(GL_TEXTURE_2D, renderedTexture);
		// Set our "renderedTexture" sampler to user Texture Unit 0
		glUniform1i(texID, 0);

		// 1rst attribute buffer : vertices
		glEnableVertexAttribArray(0);
		glBindBuffer(GL_ARRAY_BUFFER, quad_vertexbuffer);
		glVertexAttribPointer(
			0,                  // attribute 0. No particular reason for 0, but must match the layout in the shader.
			3,                  // size
			GL_FLOAT,           // type
			GL_FALSE,           // normalized?
			0,                  // stride
			(void*)0            // array buffer offset
		);

		
		// Draw the triangles !
		glDrawArrays(GL_TRIANGLES, 0, 6); // 2*3 indices starting at 0 -> 2 triangles

		glDisableVertexAttribArray(0);

		

		// Swap buffers
		glfwSwapBuffers(window);
		glfwPollEvents();

is this right?

0

Share this post


Link to post
Share on other sites

Yes, but make sure you call glBindFrameBuffer(GL_FRAMEBUFFER, 0) befor glGetTexImage (), or else it will fail. Mapping/binding textures that are attached to a bound fbo will fail.

2

Share this post


Link to post
Share on other sites

Hi!

This works!! thanks a lot!

this is the update of the previous code:

		glDisableVertexAttribArray(0);
		glDisableVertexAttribArray(1);

		// Render to the screen
		glBindFramebuffer(GL_FRAMEBUFFER, 0);
		glViewport(0,0,1024,768); // Render on the whole framebuffer, complete from the lower left corner to the upper right
		/*---------------------------------------------------------*/
		int size = 1024*768*3;
		std::vector<GLfloat> pix(size);
		glGetTexImage (GL_TEXTURE_2D, 0, GL_RGB, GL_FLOAT, &pix[0]);
		for(int c = 0; c < size; c++){	
			if (pix[c] > 0.5)
				pix[c] = 1.0; //just a little modify for try, the cube should be yellow now (it was green)
		}
		glTexSubImage2D (GL_TEXTURE_2D,0,0,0,1024,768,GL_RGB,GL_FLOAT,&pix[0]);


		/*---------------------------------------------------------*/	
		// Clear the screen
		glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
1

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!


Register a new account

Sign in

Already have an account? Sign in here.


Sign In Now
Sign in to follow this  
Followers 0

  • Similar Content

    • By DaniDesu
      #include "MyEngine.h" int main() { MyEngine myEngine; myEngine.run(); return 0; } MyEngine.h
      #pragma once #include "MyWindow.h" #include "MyShaders.h" #include "MyShapes.h" class MyEngine { private: GLFWwindow * myWindowHandle; MyWindow * myWindow; public: MyEngine(); ~MyEngine(); void run(); }; MyEngine.cpp
      #include "MyEngine.h" MyEngine::MyEngine() { MyWindow myWindow(800, 600, "My Game Engine"); this->myWindow = &myWindow; myWindow.createWindow(); this->myWindowHandle = myWindow.getWindowHandle(); // Load all OpenGL function pointers for use gladLoadGLLoader((GLADloadproc)glfwGetProcAddress); } MyEngine::~MyEngine() { this->myWindow->destroyWindow(); } void MyEngine::run() { MyShaders myShaders("VertexShader.glsl", "FragmentShader.glsl"); MyShapes myShapes; GLuint vertexArrayObjectHandle; float coordinates[] = { 0.5f, 0.5f, 0.0f, 0.5f, -0.5f, 0.0f, -0.5f, 0.5f, 0.0f }; vertexArrayObjectHandle = myShapes.drawTriangle(coordinates); while (!glfwWindowShouldClose(this->myWindowHandle)) { glClearColor(0.5f, 0.5f, 0.5f, 1.0f); glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); // Draw something glUseProgram(myShaders.getShaderProgram()); glBindVertexArray(vertexArrayObjectHandle); glDrawArrays(GL_TRIANGLES, 0, 3); glfwSwapBuffers(this->myWindowHandle); glfwPollEvents(); } } MyShaders.h
      #pragma once #include <glad\glad.h> #include <GLFW\glfw3.h> #include "MyFileHandler.h" class MyShaders { private: const char * vertexShaderFileName; const char * fragmentShaderFileName; const char * vertexShaderCode; const char * fragmentShaderCode; GLuint vertexShaderHandle; GLuint fragmentShaderHandle; GLuint shaderProgram; void compileShaders(); public: MyShaders(const char * vertexShaderFileName, const char * fragmentShaderFileName); ~MyShaders(); GLuint getShaderProgram(); const char * getVertexShaderCode(); const char * getFragmentShaderCode(); }; MyShaders.cpp
      #include "MyShaders.h" MyShaders::MyShaders(const char * vertexShaderFileName, const char * fragmentShaderFileName) { this->vertexShaderFileName = vertexShaderFileName; this->fragmentShaderFileName = fragmentShaderFileName; // Load shaders from files MyFileHandler myVertexShaderFileHandler(this->vertexShaderFileName); this->vertexShaderCode = myVertexShaderFileHandler.readFile(); MyFileHandler myFragmentShaderFileHandler(this->fragmentShaderFileName); this->fragmentShaderCode = myFragmentShaderFileHandler.readFile(); // Compile shaders this->compileShaders(); } MyShaders::~MyShaders() { } void MyShaders::compileShaders() { this->vertexShaderHandle = glCreateShader(GL_VERTEX_SHADER); this->fragmentShaderHandle = glCreateShader(GL_FRAGMENT_SHADER); glShaderSource(this->vertexShaderHandle, 1, &(this->vertexShaderCode), NULL); glShaderSource(this->fragmentShaderHandle, 1, &(this->fragmentShaderCode), NULL); glCompileShader(this->vertexShaderHandle); glCompileShader(this->fragmentShaderHandle); this->shaderProgram = glCreateProgram(); glAttachShader(this->shaderProgram, this->vertexShaderHandle); glAttachShader(this->shaderProgram, this->fragmentShaderHandle); glLinkProgram(this->shaderProgram); return; } GLuint MyShaders::getShaderProgram() { return this->shaderProgram; } const char * MyShaders::getVertexShaderCode() { return this->vertexShaderCode; } const char * MyShaders::getFragmentShaderCode() { return this->fragmentShaderCode; } MyWindow.h
      #pragma once #include <glad\glad.h> #include <GLFW\glfw3.h> class MyWindow { private: GLFWwindow * windowHandle; int windowWidth; int windowHeight; const char * windowTitle; public: MyWindow(int windowWidth, int windowHeight, const char * windowTitle); ~MyWindow(); GLFWwindow * getWindowHandle(); void createWindow(); void MyWindow::destroyWindow(); }; MyWindow.cpp
      #include "MyWindow.h" MyWindow::MyWindow(int windowWidth, int windowHeight, const char * windowTitle) { this->windowHandle = NULL; this->windowWidth = windowWidth; this->windowWidth = windowWidth; this->windowHeight = windowHeight; this->windowTitle = windowTitle; glfwInit(); } MyWindow::~MyWindow() { } GLFWwindow * MyWindow::getWindowHandle() { return this->windowHandle; } void MyWindow::createWindow() { // Use OpenGL 3.3 and GLSL 3.3 glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3); glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); // Limit backwards compatibility glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); glfwWindowHint(GLFW_OPENGL_FORWARD_COMPAT, GL_TRUE); // Prevent resizing window glfwWindowHint(GLFW_RESIZABLE, GL_FALSE); // Create window this->windowHandle = glfwCreateWindow(this->windowWidth, this->windowHeight, this->windowTitle, NULL, NULL); glfwMakeContextCurrent(this->windowHandle); } void MyWindow::destroyWindow() { glfwTerminate(); } MyShapes.h
      #pragma once #include <glad\glad.h> #include <GLFW\glfw3.h> class MyShapes { public: MyShapes(); ~MyShapes(); GLuint & drawTriangle(float coordinates[]); }; MyShapes.cpp
      #include "MyShapes.h" MyShapes::MyShapes() { } MyShapes::~MyShapes() { } GLuint & MyShapes::drawTriangle(float coordinates[]) { GLuint vertexBufferObject{}; GLuint vertexArrayObject{}; // Create a VAO glGenVertexArrays(1, &vertexArrayObject); glBindVertexArray(vertexArrayObject); // Send vertices to the GPU glGenBuffers(1, &vertexBufferObject); glBindBuffer(GL_ARRAY_BUFFER, vertexBufferObject); glBufferData(GL_ARRAY_BUFFER, sizeof(coordinates), coordinates, GL_STATIC_DRAW); // Dertermine the interpretation of the array buffer glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3*sizeof(float), (void *)0); glEnableVertexAttribArray(0); // Unbind the buffers glBindBuffer(GL_ARRAY_BUFFER, 0); glBindVertexArray(0); return vertexArrayObject; } MyFileHandler.h
      #pragma once #include <cstdio> #include <cstdlib> class MyFileHandler { private: const char * fileName; unsigned long fileSize; void setFileSize(); public: MyFileHandler(const char * fileName); ~MyFileHandler(); unsigned long getFileSize(); const char * readFile(); }; MyFileHandler.cpp
      #include "MyFileHandler.h" MyFileHandler::MyFileHandler(const char * fileName) { this->fileName = fileName; this->setFileSize(); } MyFileHandler::~MyFileHandler() { } void MyFileHandler::setFileSize() { FILE * fileHandle = NULL; fopen_s(&fileHandle, this->fileName, "rb"); fseek(fileHandle, 0L, SEEK_END); this->fileSize = ftell(fileHandle); rewind(fileHandle); fclose(fileHandle); return; } unsigned long MyFileHandler::getFileSize() { return (this->fileSize); } const char * MyFileHandler::readFile() { char * buffer = (char *)malloc((this->fileSize)+1); FILE * fileHandle = NULL; fopen_s(&fileHandle, this->fileName, "rb"); fread(buffer, this->fileSize, sizeof(char), fileHandle); fclose(fileHandle); buffer[this->fileSize] = '\0'; return buffer; } VertexShader.glsl
      #version 330 core layout (location = 0) vec3 VertexPositions; void main() { gl_Position = vec4(VertexPositions, 1.0f); } FragmentShader.glsl
      #version 330 core out vec4 FragmentColor; void main() { FragmentColor = vec4(1.0f, 0.0f, 0.0f, 1.0f); } I am attempting to create a simple engine/graphics utility using some object-oriented paradigms. My first goal is to get some output from my engine, namely, a simple red triangle.
      For this goal, the MyShapes class will be responsible for defining shapes such as triangles, polygons etc. Currently, there is only a drawTriangle() method implemented, because I first wanted to see whether it works or not before attempting to code other shape drawing methods.
      The constructor of the MyEngine class creates a GLFW window (GLAD is also initialized here to load all OpenGL functionality), and the myEngine.run() method in Main.cpp is responsible for firing up the engine. In this run() method, the shaders get loaded from files via the help of my FileHandler class. The vertices for the triangle are processed by the myShapes.drawTriangle() method where a vertex array object, a vertex buffer object and vertrex attributes are set for this purpose.
      The while loop in the run() method should be outputting me the desired red triangle, but all I get is a grey window area. Why?
      Note: The shaders are compiling and linking without any errors.
      (Note: I am aware that this code is not using any good software engineering practices (e.g. exceptions, error handling). I am planning to implement them later, once I get the hang of OpenGL.)

       
    • By KarimIO
      EDIT: I thought this was restricted to Attribute-Created GL contexts, but it isn't, so I rewrote the post.
      Hey guys, whenever I call SwapBuffers(hDC), I get a crash, and I get a "Too many posts were made to a semaphore." from Windows as I call SwapBuffers. What could be the cause of this?
      Update: No crash occurs if I don't draw, just clear and swap.
      static PIXELFORMATDESCRIPTOR pfd = // pfd Tells Windows How We Want Things To Be { sizeof(PIXELFORMATDESCRIPTOR), // Size Of This Pixel Format Descriptor 1, // Version Number PFD_DRAW_TO_WINDOW | // Format Must Support Window PFD_SUPPORT_OPENGL | // Format Must Support OpenGL PFD_DOUBLEBUFFER, // Must Support Double Buffering PFD_TYPE_RGBA, // Request An RGBA Format 32, // Select Our Color Depth 0, 0, 0, 0, 0, 0, // Color Bits Ignored 0, // No Alpha Buffer 0, // Shift Bit Ignored 0, // No Accumulation Buffer 0, 0, 0, 0, // Accumulation Bits Ignored 24, // 24Bit Z-Buffer (Depth Buffer) 0, // No Stencil Buffer 0, // No Auxiliary Buffer PFD_MAIN_PLANE, // Main Drawing Layer 0, // Reserved 0, 0, 0 // Layer Masks Ignored }; if (!(hDC = GetDC(windowHandle))) return false; unsigned int PixelFormat; if (!(PixelFormat = ChoosePixelFormat(hDC, &pfd))) return false; if (!SetPixelFormat(hDC, PixelFormat, &pfd)) return false; hRC = wglCreateContext(hDC); if (!hRC) { std::cout << "wglCreateContext Failed!\n"; return false; } if (wglMakeCurrent(hDC, hRC) == NULL) { std::cout << "Make Context Current Second Failed!\n"; return false; } ... // OGL Buffer Initialization glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT); glBindVertexArray(vao); glUseProgram(myprogram); glDrawElements(GL_TRIANGLES, indexCount, GL_UNSIGNED_SHORT, (void *)indexStart); SwapBuffers(GetDC(window_handle));  
    • By Tchom
      Hey devs!
       
      I've been working on a OpenGL ES 2.0 android engine and I have begun implementing some simple (point) lighting. I had something fairly simple working, so I tried to get fancy and added color-tinting light. And it works great... with only one or two lights. Any more than that, the application drops about 15 frames per light added (my ideal is at least 4 or 5). I know implementing lighting is expensive, I just didn't think it was that expensive. I'm fairly new to the world of OpenGL and GLSL, so there is a good chance I've written some crappy shader code. If anyone had any feedback or tips on how I can optimize this code, please let me know.
       
      Vertex Shader
      uniform mat4 u_MVPMatrix; uniform mat4 u_MVMatrix; attribute vec4 a_Position; attribute vec3 a_Normal; attribute vec2 a_TexCoordinate; varying vec3 v_Position; varying vec3 v_Normal; varying vec2 v_TexCoordinate; void main() { v_Position = vec3(u_MVMatrix * a_Position); v_TexCoordinate = a_TexCoordinate; v_Normal = vec3(u_MVMatrix * vec4(a_Normal, 0.0)); gl_Position = u_MVPMatrix * a_Position; } Fragment Shader
      precision mediump float; uniform vec4 u_LightPos["+numLights+"]; uniform vec4 u_LightColours["+numLights+"]; uniform float u_LightPower["+numLights+"]; uniform sampler2D u_Texture; varying vec3 v_Position; varying vec3 v_Normal; varying vec2 v_TexCoordinate; void main() { gl_FragColor = (texture2D(u_Texture, v_TexCoordinate)); float diffuse = 0.0; vec4 colourSum = vec4(1.0); for (int i = 0; i < "+numLights+"; i++) { vec3 toPointLight = vec3(u_LightPos[i]); float distance = length(toPointLight - v_Position); vec3 lightVector = normalize(toPointLight - v_Position); float diffuseDiff = 0.0; // The diffuse difference contributed from current light diffuseDiff = max(dot(v_Normal, lightVector), 0.0); diffuseDiff = diffuseDiff * (1.0 / (1.0 + ((1.0-u_LightPower[i])* distance * distance))); //Determine attenuatio diffuse += diffuseDiff; gl_FragColor.rgb *= vec3(1.0) / ((vec3(1.0) + ((vec3(1.0) - vec3(u_LightColours[i]))*diffuseDiff))); //The expensive part } diffuse += 0.1; //Add ambient light gl_FragColor.rgb *= diffuse; } Am I making any rookie mistakes? Or am I just being unrealistic about what I can do? Thanks in advance
    • By yahiko00
      Hi,
      Not sure to post at the right place, if not, please forgive me...
      For a game project I am working on, I would like to implement a 2D starfield as a background.
      I do not want to deal with static tiles, since I plan to slowly animate the starfield. So, I am trying to figure out how to generate a random starfield for the entire map.
      I feel that using a uniform distribution for the stars will not do the trick. Instead I would like something similar to the screenshot below, taken from the game Star Wars: Empire At War (all credits to Lucasfilm, Disney, and so on...).

      Is there someone who could have an idea of a distribution which could result in such a starfield?
      Any insight would be appreciated
    • By afraidofdark
      I have just noticed that, in quake 3 and half - life, dynamic models are effected from light map. For example in dark areas, gun that player holds seems darker. How did they achieve this effect ? I can use image based lighting techniques however (Like placing an environment probe and using it for reflections and ambient lighting), this tech wasn't used in games back then, so there must be a simpler method to do this.
      Here is a link that shows how modern engines does it. Indirect Lighting Cache It would be nice if you know a paper that explains this technique. Can I apply this to quake 3' s light map generator and bsp format ?
  • Popular Now