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OpenGL OpenGL and user defined functions/classes with c++ issues

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I'm currently learning modern OpenGL. So far I have been programming everything within the same scope of the primary cpp file, but the more I learn, the more that file becomes very lengthy and cluttered. So naturally, I have been trying to break up my code by putting some within a user defined function and even a user defined class, but I keep having the same problem in that I just have a black screen instead of a rendered triangle.

 

I am currently using Glfw3 and Glew with my code if that helps. I have also tried passing certain values, like window handles, but to no avail. If I put all the code within my user defined function in main(), the triangle becomes rendered.

 

 

Here is my code:

 

framework.h

#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <iostream>
#include <fstream>

#pragma comment(lib, "glfw3dll.lib")
#pragma comment(lib, "glew32.lib")
#pragma comment(lib, "opengl32.lib")

using namespace std;

framework.cpp

#include "framework.h"
#include "rendering.h"


int windowWidth = 800;
int windowHeight = 450;
ofstream outFile("output.txt");
renderingUtils renderingClass; //Rendering Utils Class
void renderFunction(float*, GLFWwindow*);

float triangleW = 0.125;
float triangleH = 0.125;
float coordinateX = 0.25;
float coordinateY = 0.25;
float points[24] = {
	0.0f, 0.0f, 0.0f, 1.0f,
	0.5f, 0.0f, 0.0f, 1.0f,
	0.0f, 0.5f, 0.0f, 1.0f,
	1.0f, 0.0f, 0.0f, 1.0f,
	0.0f, 1.0f, 0.0f, 1.0f,
	0.0f, 0.0f, 1.0f, 1.0f,
};
/*float points[24] = {  //Vertex Information
	coordinateX, coordinateY, 0.0f, 1.0f,
	coordinateX + triangleW, coordinateY, 0.0f, 1.0f,
	coordinateX + (triangleW / 2), coordinateY + triangleH, 0.0f, 1.0f, //First Triangle
	1.0f, 0.0f, 0.0f, 1.0f,
	0.0f, 1.0f, 0.0f, 1.0f,
	0.0f, 0.0f, 1.0f, 1.0f, //Color Information
};*/

int main(){

	//Start GL context O/S window using the GLFW helper library
	if (!glfwInit()){
		outFile << "ERROR: Could not start GLFW3\n";
		return 1;
	}

	GLFWwindow* window = glfwCreateWindow(windowWidth, windowHeight, "Tutorial Project", NULL, NULL);
	if (!window){
		outFile << "ERROR: Could not open window with GLFW3\n";
		glfwTerminate();
		return 1;
	}

	glfwMakeContextCurrent(window);

	//start GLEW extension handler
	glewExperimental = GL_TRUE;
	glewInit();

	//Get version info
	const GLubyte* renderer = glGetString(GL_RENDERER); //Get renderer string
	const GLubyte* version = glGetString(GL_VERSION); //Version as a string

	std::cout << "Renderer: " << renderer << "\n";
	std::cout << "OpenGL version supported: " << version << "\n";



	//Initialize Display
	renderFunction(points, window);



	
	while (!glfwWindowShouldClose(window)){
		//Compute Position Offsets
		//Adjust Vertex Data
		//Render Display
		//renderingClass.updateScene();





		//Update other events like input handling
		glfwPollEvents();

	}
	
	//Close GL context and any other GLFW resources
	glfwTerminate();
	getchar();
	return 0;

}

void renderFunction(float* points, GLFWwindow* window){
	glfwMakeContextCurrent(window);

	// Test Code below
	unsigned int vbo = 0;
	unsigned int vao = 0;
	unsigned int vs;
	unsigned int fs;
	unsigned int program;
	const char* vertex_shader =
		"#version 330\n"
		"layout(location = 0) in vec4 position;"
		"layout(location = 1) in vec4 color;"
		"smooth out vec4 theColor;"
		"void main () {"
		"  gl_Position = position;"
		"  theColor = color;"
		"}";
	const char* fragment_shader =
		"#version 330\n"
		"smooth in vec4 theColor;"
		"out vec4 outputColor;"
		"void main () {"
		"  outputColor = theColor;"
		"}";
	std::cout << "Scene set up.\n";
	std::cout << points[4] << "\n";
	//Tell GL to only draw onto a pixel if the shape is closer to the viewer
	glEnable(GL_DEPTH_TEST); //Enable Depth-Testing
	glDepthFunc(GL_LESS); //Depth-testing interprests a smaller value as "closer"
	glViewport(0, 0, (GLsizei)800, (GLsizei)450);

	glGenBuffers(1, &vbo); //
	glBindBuffer(GL_ARRAY_BUFFER, vbo); //
	glBufferData(GL_ARRAY_BUFFER, sizeof(points), points, GL_STATIC_DRAW); //
	glBindBuffer(GL_ARRAY_BUFFER, 0);

	glGenVertexArrays(1, &vao); //
	glBindVertexArray(vao); //
	glBindBuffer(GL_ARRAY_BUFFER, vbo);
	glEnableVertexAttribArray(0); //
	glEnableVertexAttribArray(1); //

	glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0); //
	glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, (void*)48); //


	vs = glCreateShader(GL_VERTEX_SHADER);//
	glShaderSource(vs, 1, &vertex_shader, NULL); //
	glCompileShader(vs); //

	GLint status;
	glGetShaderiv(vs, GL_COMPILE_STATUS, &status);
	if (status == GL_FALSE) { std::cout << "Compile status1: fail\n"; }
	fs = glCreateShader(GL_FRAGMENT_SHADER); //
	glShaderSource(fs, 1, &fragment_shader, NULL); //
	glCompileShader(fs); //
	GLint status2;
	glGetShaderiv(fs, GL_COMPILE_STATUS, &status2);
	if (status2 == GL_FALSE){ std::cout << "Compile status2: fail\n"; }

	program = glCreateProgram(); //
	glAttachShader(program, fs); //
	glAttachShader(program, vs); //
	glLinkProgram(program); //
	GLint status3;
	glGetProgramiv(program, GL_LINK_STATUS, &status3);
	if (status3 == GL_FALSE) { std::cout << "GL program failure \n"; }

	glClearColor(0.0f, 0.0f, 0.0f, 0.0f); //
	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //

	glUseProgram(program); //
	glBindVertexArray(vao); //
	glDrawArrays(GL_TRIANGLES, 0, 3); //

	glfwSwapBuffers(window);
}

Any ideas as why this is not working?

Edited by jccourtney

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Oe problem, at least, is your glBufferData call where you use sizeof(points). The variable points is a pointer, thus sizeof(points) is the size of the pointer. You are thus loading a buffer with, most likely, either 4 of 8 bytes of data. If you want the size of the original points array that you pass to renderFunction, you need to pass its size to the function, because once the array decays into the pointer at the call site, the size information is lost.

 

But, that aside, do not create and upload data in a render function. Make it a separate init function, and have the render function refer to the buffer objects instead.

Edited by Brother Bob

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Brother Bob, 

 

I corrected that and also adjust my code to your suggestion, but unfortunately I'm still just getting a black screen. 

 

Here's my updated framework.cpp file:

#include "framework.h"

int windowWidth = 800;
int windowHeight = 450;
ofstream outFile("output.txt");
void renderFunction(float*, GLFWwindow*, GLuint*, GLuint*, GLuint*, GLuint*, GLuint*);
void initRenderer(float*, GLFWwindow*, GLuint*, GLuint*, GLuint*, GLuint*, GLuint*);
float triangleW = 0.125;
float triangleH = 0.125;
float coordinateX = 0.25;
float coordinateY = 0.25;
float points[24] = {
	0.0f, 0.0f, 0.0f, 1.0f,
	0.5f, 0.0f, 0.0f, 1.0f,
	0.0f, 0.5f, 0.0f, 1.0f,
	1.0f, 0.0f, 0.0f, 1.0f,
	0.0f, 1.0f, 0.0f, 1.0f,
	0.0f, 0.0f, 1.0f, 1.0f,
};
GLuint vbo = 0;
GLuint vao = 0;
GLuint vs;
GLuint fs;
GLuint program;

int main(){

	//Start GL context O/S window using the GLFW helper library
	if (!glfwInit()){
		outFile << "ERROR: Could not start GLFW3\n";
		return 1;
	}

	GLFWwindow* window = glfwCreateWindow(windowWidth, windowHeight, "Tutorial Project", NULL, NULL);
	if (!window){
		outFile << "ERROR: Could not open window with GLFW3\n";
		glfwTerminate();
		return 1;
	}
	
	glfwMakeContextCurrent(window);

	//start GLEW extension handler
	glewExperimental = GL_TRUE;
	glewInit();

	//Get version info
	const GLubyte* renderer = glGetString(GL_RENDERER); //Get renderer string
	const GLubyte* version = glGetString(GL_VERSION); //Version as a string

	std::cout << "Renderer: " << renderer << "\n";
	std::cout << "OpenGL version supported: " << version << "\n";



	//Initialize Display
	initRenderer(points, window, &vbo, &vao, &vs, &fs, &program);



	
	while (!glfwWindowShouldClose(window)){
		//Compute Position Offsets
		//Adjust Vertex Data
		//Render Display
		//renderingClass.updateScene();
		renderFunction(points, window, &vbo, &vao, &vs, &fs, &program);




		//Update other events like input handling
		glfwPollEvents();

	}
	
	//Close GL context and any other GLFW resources
	glfwTerminate();
	getchar();
	return 0;

}

void renderFunction(float* points, GLFWwindow* window, GLuint* vbo, GLuint* vao, GLuint* vs, GLuint* fs, GLuint* program){
	glfwMakeContextCurrent(window);
	glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
	glClear(GL_COLOR_BUFFER_BIT);
	glUseProgram(*program);
	glBindBuffer(GL_ARRAY_BUFFER, *vbo);
	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);
	glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, (void*)48);

	glDrawArrays(GL_TRIANGLES, 0, 3);

	glDisableVertexAttribArray(0);
	glUseProgram(0);

	glfwSwapBuffers(window);

}

void initRenderer(float* points, GLFWwindow* window, GLuint* vbo, GLuint* vao, GLuint* vs, GLuint* fs, GLuint* program){
	glfwMakeContextCurrent(window);
	const char* vertex_shader =
		"#version 330\n"
		"layout(location = 0) in vec4 position;"
		"layout(location = 1) in vec4 color;"
		"smooth out vec4 theColor;"
		"void main () {"
		"  gl_Position = position;"
		"  theColor = color;"
		//vec4 (vp, 1.0);"
		"}";
	const char* fragment_shader =
		"#version 330\n"
		"smooth in vec4 theColor;"
		"out vec4 outputColor;"
		"void main () {"
		"  outputColor = theColor;"
		"}";

	//Tell GL to only draw onto a pixel if the shape is closer to the viewer
	glEnable(GL_DEPTH_TEST); //Enable Depth-Testing
	glDepthFunc(GL_LESS); //Depth-testing interprests a smaller value as "closer"
	glViewport(0, 0, (GLsizei)800, (GLsizei)450);

	glGenBuffers(1, vbo); 
	glBindBuffer(GL_ARRAY_BUFFER, *vbo); 
	glBufferData(GL_ARRAY_BUFFER, sizeof(points), points, GL_STATIC_DRAW); //
	glBindBuffer(GL_ARRAY_BUFFER, 0);

	glGenVertexArrays(1, vao);
	glBindVertexArray(*vao);
	glBindBuffer(GL_ARRAY_BUFFER, *vbo);
	glEnableVertexAttribArray(0); 
	glEnableVertexAttribArray(1); 

	glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0); 
	glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, (void*)48); 


	*vs = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(*vs, 1, &vertex_shader, NULL); 
	glCompileShader(*vs); //

	GLint status;
	glGetShaderiv(*vs, GL_COMPILE_STATUS, &status);
	if (status == GL_FALSE) { std::cout << "Compile status1: fail\n"; }
	*fs = glCreateShader(GL_FRAGMENT_SHADER); //
	glShaderSource(*fs, 1, &fragment_shader, NULL); //
	glCompileShader(*fs); //
	
	GLint status2;
	glGetShaderiv(*fs, GL_COMPILE_STATUS, &status2);
	if (status2 == GL_FALSE){ std::cout << "Compile status2: fail\n"; }

	*program = glCreateProgram(); //
	glAttachShader(*program, *fs); //
	glAttachShader(*program, *vs); //
	glLinkProgram(*program); //
	GLint status3;
	glGetProgramiv(*program, GL_LINK_STATUS, &status3);
	if (status3 == GL_FALSE) { std::cout << "GL program failure \n"; }
}
Edited by jccourtney

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I'm currently learning modern OpenGL. So far I have been programming everything within the same scope of the primary cpp file, but the more I learn, the more that file becomes very lengthy and cluttered. So naturally, I have been trying to break up my code by putting some within a user defined function and even a user defined class, but I keep having the same problem in that I just have a black screen instead of a rendered triangle.

 

Sorry, I don't have a specific answer to your question. You have the experienced the black screen of death in OpenGL. There are quite a lot of single point of failures when programming OpenGL, and many of them will give you a black screen.

 

My personal experience is to do as follows:

  1. Whenever something works, I check it in to a version control.
  2. I make many small check ins, making it easy to back step when something stops working.
  3. I make sure every small step still works.

This relates not only to OpenGL, of course. Now and then, I grow more confident as I feel I have enough experience. And then I suddenly have to spend a lot of time debugging and try to understand why something was broken.

 

Otherwise, I would say you are on the right path. That is, you need to create a library/framework for using OpenGL (or use a library from someone else). OpenGL is low level programming, and it has helped me to add some layers above it.

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You didn't correct the error I mentioned. In initRenderer, you are still taking the size of the pointer in the call to glBufferData, not the size of the original array data; points is still a pointer, and sizeof(points) still returns the size of the pointer which is likely either 4 or 8 bytes. You need to pass the size of the array data to initRenderer, because it cannot know the size of the original array by the pointer alone.

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You didn't correct the error I mentioned. In initRenderer, you are still taking the size of the pointer in the call to glBufferData, not the size of the original array data; points is still a pointer, and sizeof(points) still returns the size of the pointer which is likely either 4 or 8 bytes. You need to pass the size of the array data to initRenderer, because it cannot know the size of the original array by the pointer alone.

Brother Bob, I updated the code to include the hard coded value of the array length and sizeof(float) in the glBufferData call. I also changed the prototype and declaration sections to use float points[] instead of float* points.



#include "framework.h"

int windowWidth = 800;
int windowHeight = 450;
ofstream outFile("output.txt");
void renderFunction(float[], GLFWwindow*, GLuint*, GLuint*, GLuint*, GLuint*, GLuint*);
void initRenderer(float[], GLFWwindow*, GLuint*, GLuint*, GLuint*, GLuint*, GLuint*);
float triangleW = 0.125;
float triangleH = 0.125;
float coordinateX = 0.25;
float coordinateY = 0.25;
float points[24] = {
	0.0f, 0.0f, 0.0f, 1.0f,
	0.5f, 0.0f, 0.0f, 1.0f,
	0.0f, 0.5f, 0.0f, 1.0f,
	1.0f, 0.0f, 0.0f, 1.0f,
	0.0f, 1.0f, 0.0f, 1.0f,
	0.0f, 0.0f, 1.0f, 1.0f,
};
GLuint vbo = 0;
GLuint vao = 0;
GLuint vs;
GLuint fs;
GLuint program;



/*float points[24] = {  //Vertex Information
	coordinateX, coordinateY, 0.0f, 1.0f,
	coordinateX + triangleW, coordinateY, 0.0f, 1.0f,
	coordinateX + (triangleW / 2), coordinateY + triangleH, 0.0f, 1.0f, //First Triangle
	1.0f, 0.0f, 0.0f, 1.0f,
	0.0f, 1.0f, 0.0f, 1.0f,
	0.0f, 0.0f, 1.0f, 1.0f, //Color Information
};*/

int main(){
	//Start GL context O/S window using the GLFW helper library
	if (!glfwInit()){
		outFile << "ERROR: Could not start GLFW3\n";
		return 1;
	}

	GLFWwindow* window = glfwCreateWindow(windowWidth, windowHeight, "Tutorial Project", NULL, NULL);
	if (!window){
		outFile << "ERROR: Could not open window with GLFW3\n";
		glfwTerminate();
		return 1;
	}
	
	glfwMakeContextCurrent(window);

	//start GLEW extension handler
	glewExperimental = GL_TRUE;
	glewInit();

	//Get version info
	const GLubyte* renderer = glGetString(GL_RENDERER); //Get renderer string
	const GLubyte* version = glGetString(GL_VERSION); //Version as a string

	std::cout << "Renderer: " << renderer << "\n";
	std::cout << "OpenGL version supported: " << version << "\n";



	//Initialize Display
	initRenderer(points, window, &vbo, &vao, &vs, &fs, &program);



	
	while (!glfwWindowShouldClose(window)){

		renderFunction(points, window, &vbo, &vao, &vs, &fs, &program);




		//Update other events like input handling
		glfwPollEvents();

	}
	
	//Close GL context and any other GLFW resources
	glfwTerminate();
	getchar();
	return 0;

}

void renderFunction(float points[], GLFWwindow* window, GLuint* vbo, GLuint* vao, GLuint* vs, GLuint* fs, GLuint* program){
	glfwMakeContextCurrent(window);
	glClearColor(0.0f, 0.0f, 0.3f, 0.0f);
	glClear(GL_COLOR_BUFFER_BIT);
	glUseProgram(*program);
	glBindBuffer(GL_ARRAY_BUFFER, *vbo);
	glEnableVertexAttribArray(0);
	glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0);
	glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, (void*)48);

	glDrawArrays(GL_TRIANGLES, 0, 3);

	glDisableVertexAttribArray(0);
	glUseProgram(0);

	glfwSwapBuffers(window);

}

void initRenderer(float points[], GLFWwindow* window, GLuint* vbo, GLuint* vao, GLuint* vs, GLuint* fs, GLuint* program){
	glfwMakeContextCurrent(window);
	const char* vertex_shader =
		"#version 330\n"
		"layout(location = 0) in vec4 position;"
		"layout(location = 1) in vec4 color;"
		"smooth out vec4 theColor;"
		"void main () {"
		"  gl_Position = position;"
		"  theColor = color;"
		"}";
	const char* fragment_shader =
		"#version 330\n"
		"smooth in vec4 theColor;"
		"out vec4 outputColor;"
		"void main () {"
		"  outputColor = theColor;"
		"}";

	//Tell GL to only draw onto a pixel if the shape is closer to the viewer
	glEnable(GL_DEPTH_TEST); //Enable Depth-Testing
	glDepthFunc(GL_LESS); //Depth-testing interprests a smaller value as "closer"
	glViewport(0, 0, (GLsizei)800, (GLsizei)450);

	glGenBuffers(1, vbo); 
	glBindBuffer(GL_ARRAY_BUFFER, *vbo); 
	glBufferData(GL_ARRAY_BUFFER, 24*sizeof(float), points, GL_STATIC_DRAW); //
	glBindBuffer(GL_ARRAY_BUFFER, 0);


	glGenVertexArrays(1, vao);
	glBindVertexArray(*vao);
	glBindBuffer(GL_ARRAY_BUFFER, *vao);
	glEnableVertexAttribArray(0); 
	glEnableVertexAttribArray(1); 

	glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, 0, 0); 
	glVertexAttribPointer(1, 4, GL_FLOAT, GL_FALSE, 0, (void*)48); 


	*vs = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(*vs, 1, &vertex_shader, NULL); 
	glCompileShader(*vs); //

	GLint status;
	glGetShaderiv(*vs, GL_COMPILE_STATUS, &status);
	if (status == GL_FALSE) { std::cout << "Compile status1: fail\n"; }
	*fs = glCreateShader(GL_FRAGMENT_SHADER); //
	glShaderSource(*fs, 1, &fragment_shader, NULL); //
	glCompileShader(*fs); //
	
	GLint status2;
	glGetShaderiv(*fs, GL_COMPILE_STATUS, &status2);
	if (status2 == GL_FALSE){ std::cout << "Compile status2: fail\n"; }

	*program = glCreateProgram(); //
	glAttachShader(*program, *fs); //
	glAttachShader(*program, *vs); //
	glLinkProgram(*program); //
	GLint status3;
	glGetProgramiv(*program, GL_LINK_STATUS, &status3);
	if (status3 == GL_FALSE) { std::cout << "GL program failure \n"; }
}

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glBindBuffer(GL_ARRAY_BUFFER, *vao);

Here, in initRenderer (line 144) you're attempting to bind a VAO as a VBO. Try using *vbo there.

 

In your renderFunction it looks like you're rendering with the VBO but your VAO is still bound. Pick one or the other. If you want to render with the VBO directly (and this is preferred to VAOs anyway), then disable your VAO before calling your renderFunction.

 

Your clear color is also fully transparent. You probably want a 1.0f as the last component.

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Using the above code, I found that by simply deleting the lines below or even changing the second line to GL_ALWAYS,  I managed to produce a rendered triangle.

	glEnable(GL_DEPTH_TEST); //Enable Depth-Testing
	glDepthFunc(GL_LESS); //Depth-testing interprets a smaller value as "closer" 

Now the question is why? I checked my vertex data, which is the first half of the array points, and I used a z value of 0. Does anyone have any ideas?

 

UPDATE:

 

I changed line 96, while not implementing my findings as above, from

glClear(GL_COLOR_BUFFER_BIT);

to

glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);

and I was able to get a rendered triangle.

Edited by jccourtney

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glBindBuffer(GL_ARRAY_BUFFER, *vao);

Here, in initRenderer (line 144) you're attempting to bind a VAO as a VBO. Try using *vbo there.

 

In your renderFunction it looks like you're rendering with the VBO but your VAO is still bound. Pick one or the other. If you want to render with the VBO directly (and this is preferred to VAOs anyway), then disable your VAO before calling your renderFunction.

 

Your clear color is also fully transparent. You probably want a 1.0f as the last component.

 

Thanks! I'll go ahead and make those two changes with the glClearColor call and line 144. Can you explain a little more what you mean by rendering with the VBO directly? I've tried looking online for some more information, but so far I haven't found anything useful that doesn't include VAOs. 

 

 

My basic understanding for rendering (the loop, not the initial setup) is, assuming a static draw, the following:

...
glBindVertexArray(vertexArrayObject);
glBindBuffer(GL_ARRAY_BUFFER, vertexBufferObject1);

glEnableVertexAttribArray(0);


glBindBuffer(GL_ARRAY_BUFFER, vertexBufferObjectN); //Any remaining vbos that might contain color information, etc
glEnableVertexAttribArray(N); //For any additional indexes, such as if there were an additional one for color, etc
glVertexAttribPointer(N, 4, GL_FLOAT, GL_FALSE, 0, 0); //For any additional indexes and buffers

glUseProgram(program);
glDrawArrays(GL_TRIANGLES, 0, 3);

//Clean up functions to follow

Is anything incorrect or redundant here? Thanks!

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      at the points of the horizon, when the quad is connected
      to the skybox. However, I get skew effects. Does anybody has done sth similar?
      Is there any good practice?
      Thanks everyone!
    • By iArtist93
      I'm trying to implement PBR into my simple OpenGL renderer and trying to use multiple lighting passes, I'm using one pass per light for rendering as follow:
      1- First pass = depth
      2- Second pass = ambient
      3- [3 .. n] for all the lights in the scene.
      I'm using the blending function glBlendFunc(GL_ONE, GL_ONE) for passes [3..n], and i'm doing a Gamma Correction at the end of each fragment shader.
      But i still have a problem with the output image it just looks noisy specially when i'm using texture maps.
      Is there anything wrong with those steps or is there any improvement to this process?
    • By babaliaris
      Hello Everyone!
      I'm learning openGL, and currently i'm making a simple 2D game engine to test what I've learn so far.  In order to not say to much, i made a video in which i'm showing you the behavior of the rendering.
      Video: 
       
      What i was expecting to happen, was the player moving around. When i render only the player, he moves as i would expect. When i add a second Sprite object, instead of the Player, this new sprite object is moving and finally if i add a third Sprite object the third one is moving. And the weird think is that i'm transforming the Vertices of the Player so why the transformation is being applied somewhere else?
       
      Take a look at my code:
      Sprite Class
      (You mostly need to see the Constructor, the Render Method and the Move Method)
      #include "Brain.h" #include <glm/gtc/matrix_transform.hpp> #include <vector> struct Sprite::Implementation { //Position. struct pos pos; //Tag. std::string tag; //Texture. Texture *texture; //Model matrix. glm::mat4 model; //Vertex Array Object. VertexArray *vao; //Vertex Buffer Object. VertexBuffer *vbo; //Layout. VertexBufferLayout *layout; //Index Buffer Object. IndexBuffer *ibo; //Shader. Shader *program; //Brains. std::vector<Brain *> brains; //Deconstructor. ~Implementation(); }; Sprite::Sprite(std::string image_path, std::string tag, float x, float y) { //Create Pointer To Implementaion. m_Impl = new Implementation(); //Set the Position of the Sprite object. m_Impl->pos.x = x; m_Impl->pos.y = y; //Set the tag. m_Impl->tag = tag; //Create The Texture. m_Impl->texture = new Texture(image_path); //Initialize the model Matrix. m_Impl->model = glm::mat4(1.0f); //Get the Width and the Height of the Texture. int width = m_Impl->texture->GetWidth(); int height = m_Impl->texture->GetHeight(); //Create the Verticies. float verticies[] = { //Positions //Texture Coordinates. x, y, 0.0f, 0.0f, x + width, y, 1.0f, 0.0f, x + width, y + height, 1.0f, 1.0f, x, y + height, 0.0f, 1.0f }; //Create the Indicies. unsigned int indicies[] = { 0, 1, 2, 2, 3, 0 }; //Create Vertex Array. m_Impl->vao = new VertexArray(); //Create the Vertex Buffer. m_Impl->vbo = new VertexBuffer((void *)verticies, sizeof(verticies)); //Create The Layout. m_Impl->layout = new VertexBufferLayout(); m_Impl->layout->PushFloat(2); m_Impl->layout->PushFloat(2); m_Impl->vao->AddBuffer(m_Impl->vbo, m_Impl->layout); //Create the Index Buffer. m_Impl->ibo = new IndexBuffer(indicies, 6); //Create the new shader. m_Impl->program = new Shader("Shaders/SpriteShader.shader"); } //Render. void Sprite::Render(Window * window) { //Create the projection Matrix based on the current window width and height. glm::mat4 proj = glm::ortho(0.0f, (float)window->GetWidth(), 0.0f, (float)window->GetHeight(), -1.0f, 1.0f); //Set the MVP Uniform. m_Impl->program->setUniformMat4f("u_MVP", proj * m_Impl->model); //Run All The Brains (Scripts) of this game object (sprite). for (unsigned int i = 0; i < m_Impl->brains.size(); i++) { //Get Current Brain. Brain *brain = m_Impl->brains[i]; //Call the start function only once! if (brain->GetStart()) { brain->SetStart(false); brain->Start(); } //Call the update function every frame. brain->Update(); } //Render. window->GetRenderer()->Draw(m_Impl->vao, m_Impl->ibo, m_Impl->texture, m_Impl->program); } void Sprite::Move(float speed, bool left, bool right, bool up, bool down) { if (left) { m_Impl->pos.x -= speed; m_Impl->model = glm::translate(m_Impl->model, glm::vec3(-speed, 0, 0)); } if (right) { m_Impl->pos.x += speed; m_Impl->model = glm::translate(m_Impl->model, glm::vec3(speed, 0, 0)); } if (up) { m_Impl->pos.y += speed; m_Impl->model = glm::translate(m_Impl->model, glm::vec3(0, speed, 0)); } if (down) { m_Impl->pos.y -= speed; m_Impl->model = glm::translate(m_Impl->model, glm::vec3(0, -speed, 0)); } } void Sprite::AddBrain(Brain * brain) { //Push back the brain object. m_Impl->brains.push_back(brain); } pos *Sprite::GetPos() { return &m_Impl->pos; } std::string Sprite::GetTag() { return m_Impl->tag; } int Sprite::GetWidth() { return m_Impl->texture->GetWidth(); } int Sprite::GetHeight() { return m_Impl->texture->GetHeight(); } Sprite::~Sprite() { delete m_Impl; } //Implementation Deconstructor. Sprite::Implementation::~Implementation() { delete texture; delete vao; delete vbo; delete layout; delete ibo; delete program; }  
      Renderer Class
      #include "Renderer.h" #include "Error.h" Renderer::Renderer() { } Renderer::~Renderer() { } void Renderer::Draw(VertexArray * vao, IndexBuffer * ibo, Texture *texture, Shader * program) { vao->Bind(); ibo->Bind(); program->Bind(); if (texture != NULL) texture->Bind(); GLCall(glDrawElements(GL_TRIANGLES, ibo->GetCount(), GL_UNSIGNED_INT, NULL)); } void Renderer::Clear(float r, float g, float b) { GLCall(glClearColor(r, g, b, 1.0)); GLCall(glClear(GL_COLOR_BUFFER_BIT)); } void Renderer::Update(GLFWwindow *window) { /* Swap front and back buffers */ glfwSwapBuffers(window); /* Poll for and process events */ glfwPollEvents(); }  
      Shader Code
      #shader vertex #version 330 core layout(location = 0) in vec4 aPos; layout(location = 1) in vec2 aTexCoord; out vec2 t_TexCoord; uniform mat4 u_MVP; void main() { gl_Position = u_MVP * aPos; t_TexCoord = aTexCoord; } #shader fragment #version 330 core out vec4 aColor; in vec2 t_TexCoord; uniform sampler2D u_Texture; void main() { aColor = texture(u_Texture, t_TexCoord); } Also i'm pretty sure that every time i'm hitting the up, down, left and right arrows on the keyboard, i'm changing the model Matrix of the Player and not the others.
       
      Window Class:
      #include "Window.h" #include <GL/glew.h> #include <GLFW/glfw3.h> #include "Error.h" #include "Renderer.h" #include "Scene.h" #include "Input.h" //Global Variables. int screen_width, screen_height; //On Window Resize. void OnWindowResize(GLFWwindow *window, int width, int height); //Implementation Structure. struct Window::Implementation { //GLFW Window. GLFWwindow *GLFW_window; //Renderer. Renderer *renderer; //Delta Time. double delta_time; //Frames Per Second. int fps; //Scene. Scene *scnene; //Input. Input *input; //Deconstructor. ~Implementation(); }; //Window Constructor. Window::Window(std::string title, int width, int height) { //Initializing width and height. screen_width = width; screen_height = height; //Create Pointer To Implementation. m_Impl = new Implementation(); //Try initializing GLFW. if (!glfwInit()) { std::cout << "GLFW could not be initialized!" << std::endl; std::cout << "Press ENTER to exit..." << std::endl; std::cin.get(); exit(-1); } //Setting up OpenGL Version 3.3 Core Profile. glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3); glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3); glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE); /* Create a windowed mode window and its OpenGL context */ m_Impl->GLFW_window = glfwCreateWindow(width, height, title.c_str(), NULL, NULL); if (!m_Impl->GLFW_window) { std::cout << "GLFW could not create a window!" << std::endl; std::cout << "Press ENTER to exit..." << std::endl; std::cin.get(); glfwTerminate(); exit(-1); } /* Make the window's context current */ glfwMakeContextCurrent(m_Impl->GLFW_window); //Initialize GLEW. if(glewInit() != GLEW_OK) { std::cout << "GLEW could not be initialized!" << std::endl; std::cout << "Press ENTER to exit..." << std::endl; std::cin.get(); glfwTerminate(); exit(-1); } //Enabling Blending. GLCall(glEnable(GL_BLEND)); GLCall(glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA)); //Setting the ViewPort. GLCall(glViewport(0, 0, width, height)); //**********Initializing Implementation**********// m_Impl->renderer = new Renderer(); m_Impl->delta_time = 0.0; m_Impl->fps = 0; m_Impl->input = new Input(this); //**********Initializing Implementation**********// //Set Frame Buffer Size Callback. glfwSetFramebufferSizeCallback(m_Impl->GLFW_window, OnWindowResize); } //Window Deconstructor. Window::~Window() { delete m_Impl; } //Window Main Loop. void Window::MainLoop() { //Time Variables. double start_time = 0, end_time = 0, old_time = 0, total_time = 0; //Frames Counter. int frames = 0; /* Loop until the user closes the window */ while (!glfwWindowShouldClose(m_Impl->GLFW_window)) { old_time = start_time; //Total time of previous frame. start_time = glfwGetTime(); //Current frame start time. //Calculate the Delta Time. m_Impl->delta_time = start_time - old_time; //Get Frames Per Second. if (total_time >= 1) { m_Impl->fps = frames; total_time = 0; frames = 0; } //Clearing The Screen. m_Impl->renderer->Clear(0, 0, 0); //Render The Scene. if (m_Impl->scnene != NULL) m_Impl->scnene->Render(this); //Updating the Screen. m_Impl->renderer->Update(m_Impl->GLFW_window); //Increasing frames counter. frames++; //End Time. end_time = glfwGetTime(); //Total time after the frame completed. total_time += end_time - start_time; } //Terminate GLFW. glfwTerminate(); } //Load Scene. void Window::LoadScene(Scene * scene) { //Set the scene. m_Impl->scnene = scene; } //Get Delta Time. double Window::GetDeltaTime() { return m_Impl->delta_time; } //Get FPS. int Window::GetFPS() { return m_Impl->fps; } //Get Width. int Window::GetWidth() { return screen_width; } //Get Height. int Window::GetHeight() { return screen_height; } //Get Input. Input * Window::GetInput() { return m_Impl->input; } Renderer * Window::GetRenderer() { return m_Impl->renderer; } GLFWwindow * Window::GetGLFWindow() { return m_Impl->GLFW_window; } //Implementation Deconstructor. Window::Implementation::~Implementation() { delete renderer; delete input; } //OnWindowResize void OnWindowResize(GLFWwindow *window, int width, int height) { screen_width = width; screen_height = height; //Updating the ViewPort. GLCall(glViewport(0, 0, width, height)); }  
      Brain Class
      #include "Brain.h" #include "Sprite.h" #include "Window.h" struct Brain::Implementation { //Just A Flag. bool started; //Window Pointer. Window *window; //Sprite Pointer. Sprite *sprite; }; Brain::Brain(Window *window, Sprite *sprite) { //Create Pointer To Implementation. m_Impl = new Implementation(); //Initialize Implementation. m_Impl->started = true; m_Impl->window = window; m_Impl->sprite = sprite; } Brain::~Brain() { //Delete Pointer To Implementation. delete m_Impl; } void Brain::Start() { } void Brain::Update() { } Window * Brain::GetWindow() { return m_Impl->window; } Sprite * Brain::GetSprite() { return m_Impl->sprite; } bool Brain::GetStart() { return m_Impl->started; } void Brain::SetStart(bool value) { m_Impl->started = value; } Script Class (Its a Brain Subclass!!!)
      #include "Script.h" Script::Script(Window *window, Sprite *sprite) : Brain(window, sprite) { } Script::~Script() { } void Script::Start() { std::cout << "Game Started!" << std::endl; } void Script::Update() { Input *input = this->GetWindow()->GetInput(); Sprite *sp = this->GetSprite(); //Move this sprite. this->GetSprite()->Move(200 * this->GetWindow()->GetDeltaTime(), input->GetKeyDown("left"), input->GetKeyDown("right"), input->GetKeyDown("up"), input->GetKeyDown("down")); std::cout << sp->GetTag().c_str() << ".x = " << sp->GetPos()->x << ", " << sp->GetTag().c_str() << ".y = " << sp->GetPos()->y << std::endl; }  
      Main:
      #include "SpaceShooterEngine.h" #include "Script.h" int main() { Window w("title", 600,600); Scene *scene = new Scene(); Sprite *player = new Sprite("Resources/Images/player.png", "Player", 100,100); Sprite *other = new Sprite("Resources/Images/cherno.png", "Other", 400, 100); Sprite *other2 = new Sprite("Resources/Images/cherno.png", "Other", 300, 400); Brain *brain = new Script(&w, player); player->AddBrain(brain); scene->AddSprite(player); scene->AddSprite(other); scene->AddSprite(other2); w.LoadScene(scene); w.MainLoop(); return 0; }  
       
      I literally can't find what is wrong. If you need more code, ask me to post it. I will also attach all the source files.
      Brain.cpp
      Error.cpp
      IndexBuffer.cpp
      Input.cpp
      Renderer.cpp
      Scene.cpp
      Shader.cpp
      Sprite.cpp
      Texture.cpp
      VertexArray.cpp
      VertexBuffer.cpp
      VertexBufferLayout.cpp
      Window.cpp
      Brain.h
      Error.h
      IndexBuffer.h
      Input.h
      Renderer.h
      Scene.h
      Shader.h
      SpaceShooterEngine.h
      Sprite.h
      Texture.h
      VertexArray.h
      VertexBuffer.h
      VertexBufferLayout.h
      Window.h
    • By Cristian Decu
      Hello fellow programmers,
      For a couple of days now i've decided to build my own planet renderer just to see how floating point precision issues
      can be tackled. As you probably imagine, i've quickly faced FPP issues when trying to render absurdly large planets.
       
      I have used the classical quadtree LOD approach;
      I've generated my grids with 33 vertices, (x: -1 to 1, y: -1 to 1, z = 0).
      Each grid is managed by a TerrainNode class that, depending on the side it represents (top, bottom, left right, front, back),
      creates a special rotation-translation matrix that moves and rotates the grid away from the origin so that when i finally
      normalize all the vertices on my vertex shader i can get a perfect sphere.
      T = glm::translate(glm::dmat4(1.0), glm::dvec3(0.0, 0.0, 1.0)); R = glm::rotate(glm::dmat4(1.0), glm::radians(180.0), glm::dvec3(1.0, 0.0, 0.0)); sides[0] = new TerrainNode(1.0, radius, T * R, glm::dvec2(0.0, 0.0), new TerrainTile(1.0, SIDE_FRONT)); T = glm::translate(glm::dmat4(1.0), glm::dvec3(0.0, 0.0, -1.0)); R = glm::rotate(glm::dmat4(1.0), glm::radians(0.0), glm::dvec3(1.0, 0.0, 0.0)); sides[1] = new TerrainNode(1.0, radius, R * T, glm::dvec2(0.0, 0.0), new TerrainTile(1.0, SIDE_BACK)); // So on and so forth for the rest of the sides As you can see, for the front side grid, i rotate it 180 degrees to make it face the camera and push it towards the eye;
      the back side is handled almost the same way only that i don't need to rotate it but simply push it away from the eye.
      The same technique is applied for the rest of the faces (obviously, with the proper rotations / translations).
      The matrix that result from the multiplication of R and T (in that particular order) is send to my vertex shader as `r_Grid'.
      // spherify vec3 V = normalize((r_Grid * vec4(r_Vertex, 1.0)).xyz); gl_Position = r_ModelViewProjection * vec4(V, 1.0); The `r_ModelViewProjection' matrix is generated on the CPU in this manner.
      // No the most efficient way, but it works. glm::dmat4 Camera::getMatrix() { // Create the view matrix // Roll, Yaw and Pitch are all quaternions. glm::dmat4 View = glm::toMat4(Roll) * glm::toMat4(Pitch) * glm::toMat4(Yaw); // The model matrix is generated by translating in the oposite direction of the camera. glm::dmat4 Model = glm::translate(glm::dmat4(1.0), -Position); // Projection = glm::perspective(fovY, aspect, zNear, zFar); // zNear = 0.1, zFar = 1.0995116e12 return Projection * View * Model; } I managed to get rid of z-fighting by using a technique called Logarithmic Depth Buffer described in this article; it works amazingly well, no z-fighting at all, at least not visible.
      Each frame i'm rendering each node by sending the generated matrices this way.
      // set the r_ModelViewProjection uniform // Sneak in the mRadiusMatrix which is a matrix that contains the radius of my planet. Shader::setUniform(0, Camera::getInstance()->getMatrix() * mRadiusMatrix); // set the r_Grid matrix uniform i created earlier. Shader::setUniform(1, r_Grid); grid->render(); My planet's radius is around 6400000.0 units, absurdly large, but that's what i really want to achieve;
      Everything works well, the node's split and merge as you'd expect, however whenever i get close to the surface
      of the planet the rounding errors start to kick in giving me that lovely stairs effect.
      I've read that if i could render each grid relative to the camera i could get better precision on the surface, effectively
      getting rid of those rounding errors.
       
      My question is how can i achieve this relative to camera rendering in my scenario here?
      I know that i have to do most of the work on the CPU with double, and that's exactly what i'm doing.
      I only use double on the CPU side where i also do most of the matrix multiplications.
      As you can see from my vertex shader i only do the usual r_ModelViewProjection * (some vertex coords).
       
      Thank you for your suggestions!
       
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