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jccourtney

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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      Right now, I'm working on a graphics abstraction layer for .NET which supports D3D11, Vulkan, and OpenGL at the moment. I have implemented most of my planned features already, and things are working well. Some remaining features that I am planning are Compute Shaders, and some flavor of read-write shader resources. At the moment, my shaders can just get simple read-only access to a uniform (or constant) buffer, a texture, or a sampler. Unfortunately, I'm having a tough time grasping the distinctions between all of the different kinds of read-write resources that are available. In D3D alone, there seem to be 5 or 6 different kinds of resources with similar but different characteristics. On top of that, I get the impression that some of them are more or less "obsoleted" by the newer kinds, and don't have much of a place in modern code. There seem to be a few pivots:
      The data source/destination (buffer or texture) Read-write or read-only Structured or unstructured (?) Ordered vs unordered (?) These are just my observations based on a lot of MSDN and OpenGL doc reading. For my library, I'm not interested in exposing every possibility to the user -- just trying to find a good "middle-ground" that can be represented cleanly across API's which is good enough for common scenarios.
      Can anyone give a sort of "overview" of the different options, and perhaps compare/contrast the concepts between Direct3D, OpenGL, and Vulkan? I'd also be very interested in hearing how other folks have abstracted these concepts in their libraries.
    • By aejt
      I recently started getting into graphics programming (2nd try, first try was many years ago) and I'm working on a 3d rendering engine which I hope to be able to make a 3D game with sooner or later. I have plenty of C++ experience, but not a lot when it comes to graphics, and while it's definitely going much better this time, I'm having trouble figuring out how assets are usually handled by engines.
      I'm not having trouble with handling the GPU resources, but more so with how the resources should be defined and used in the system (materials, models, etc).
      This is my plan now, I've implemented most of it except for the XML parts and factories and those are the ones I'm not sure of at all:
      I have these classes:
      For GPU resources:
      Geometry: holds and manages everything needed to render a geometry: VAO, VBO, EBO. Texture: holds and manages a texture which is loaded into the GPU. Shader: holds and manages a shader which is loaded into the GPU. For assets relying on GPU resources:
      Material: holds a shader resource, multiple texture resources, as well as uniform settings. Mesh: holds a geometry and a material. Model: holds multiple meshes, possibly in a tree structure to more easily support skinning later on? For handling GPU resources:
      ResourceCache<T>: T can be any resource loaded into the GPU. It owns these resources and only hands out handles to them on request (currently string identifiers are used when requesting handles, but all resources are stored in a vector and each handle only contains resource's index in that vector) Resource<T>: The handles given out from ResourceCache. The handles are reference counted and to get the underlying resource you simply deference like with pointers (*handle).  
      And my plan is to define everything into these XML documents to abstract away files:
      Resources.xml for ref-counted GPU resources (geometry, shaders, textures) Resources are assigned names/ids and resource files, and possibly some attributes (what vertex attributes does this geometry have? what vertex attributes does this shader expect? what uniforms does this shader use? and so on) Are reference counted using ResourceCache<T> Assets.xml for assets using the GPU resources (materials, meshes, models) Assets are not reference counted, but they hold handles to ref-counted resources. References the resources defined in Resources.xml by names/ids. The XMLs are loaded into some structure in memory which is then used for loading the resources/assets using factory classes:
      Factory classes for resources:
      For example, a texture factory could contain the texture definitions from the XML containing data about textures in the game, as well as a cache containing all loaded textures. This means it has mappings from each name/id to a file and when asked to load a texture with a name/id, it can look up its path and use a "BinaryLoader" to either load the file and create the resource directly, or asynchronously load the file's data into a queue which then can be read from later to create the resources synchronously in the GL context. These factories only return handles.
      Factory classes for assets:
      Much like for resources, these classes contain the definitions for the assets they can load. For example, with the definition the MaterialFactory will know which shader, textures and possibly uniform a certain material has, and with the help of TextureFactory and ShaderFactory, it can retrieve handles to the resources it needs (Shader + Textures), setup itself from XML data (uniform values), and return a created instance of requested material. These factories return actual instances, not handles (but the instances contain handles).
       
       
      Is this a good or commonly used approach? Is this going to bite me in the ass later on? Are there other more preferable approaches? Is this outside of the scope of a 3d renderer and should be on the engine side? I'd love to receive and kind of advice or suggestions!
      Thanks!
    • By nedondev
      I 'm learning how to create game by using opengl with c/c++ coding, so here is my fist game. In video description also have game contain in Dropbox. May be I will make it better in future.
      Thanks.
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