C++

Forum

 
glDrawElement error

Student555 (48)
I have a minor, but annoying problem. Whenever I exit my program, I get a Unhandled exception at 0x52f3be60. The command prompt does not spit out any error messages, so I do not know what the problem might be. After I exit the program, an arrow points to the line that has the glDrawElement() command. The arrow says
"this is the next statement to execute when this thread returns from the current function". I have no clue what would cause this error. Could an experienced OpenGL programmer give a second look.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
 
#include <SFML\Graphics.hpp>
#include <GL\glew.h>
#include <iostream>

using std::cout;
using std::endl;

GLuint compile_shader()
{
	static const GLchar * vertex_shader_source[] = 
	{
		"#version 400 core														\n"
		"																		\n"
		"layout(location = 0) in vec3 position;									\n"
		"layout(location = 1) in vec3 input_color;								\n"
		"																		\n"
		"out vec3 output_color;													\n"
		"																		\n"
		"void main(void)														\n"
		"{																		\n"
		"	output_color = input_color;											\n"
		" gl_Position = vec4(position.x, position.y, position.z, 1.0f);		    \n"
		"}																		\n"
	
	
	};

	static const GLchar * fragment_shader_source[] = 
	{
		"#version 400 core						\n"
		"										\n"
		"in vec3 output_color;					\n"
		"										\n"
		"out vec3 color;						\n"
		"										\n"
		"void main(void)						\n"
		"{										\n"
		"										\n"
		"  color = output_color;				\n"
		"}										\n"
	
	};


	GLuint vertex_shader = glCreateShader(GL_VERTEX_SHADER);
	glShaderSource(vertex_shader, 1, vertex_shader_source, nullptr);
	glCompileShader(vertex_shader);

	GLuint fragment_shader = glCreateShader(GL_FRAGMENT_SHADER);
	glShaderSource(fragment_shader, 1, fragment_shader_source, nullptr);
	glCompileShader(fragment_shader);

	GLint success1;
	GLchar info1[512];
	glGetShaderiv(vertex_shader, GL_COMPILE_STATUS, &success1);

	if(!success1)
	{
		glGetShaderInfoLog(vertex_shader, 512, nullptr, info1);
		for(int i = 0; i < 2; i++)
			cout << info1;
	}


	GLint success2;
	GLchar info2[512];
	glGetShaderiv(fragment_shader, GL_COMPILE_STATUS, &success2);

	if(!success2)
	{
		glGetShaderInfoLog(fragment_shader, 512, nullptr, info2);
		for(int i = 0; i < 2; i++)
			cout << info2;
	}

	GLuint shaderProgram = glCreateProgram();
	glAttachShader(shaderProgram, vertex_shader);
	glAttachShader(shaderProgram, fragment_shader);
	glLinkProgram(shaderProgram);

	GLint success3;
	GLchar info3[512];
	glGetProgramiv(shaderProgram, GL_LINK_STATUS, &success3);

	if(!success3)
	{
		glGetProgramInfoLog(shaderProgram, 512, nullptr, info3);
		for(int i = 0; i < 2; i++)
			cout << info3;
	
	}

	glDetachShader(shaderProgram, vertex_shader);
	glDetachShader(shaderProgram, fragment_shader);

	glDeleteShader(vertex_shader);
	glDeleteShader(fragment_shader);

	return shaderProgram;
}


int main()
{
	sf::RenderWindow Window(sf::VideoMode(800, 600), "OpenGL EBO");

	if(GLEW_OK != glewInit())
		cout << "Error! Could not initialize Glew" << endl;

	const GLfloat vertices[] = 
	{
		0.5f,  0.5f, 0.0f,    // TR
		0.5f, -0.5f, 0.0f,    // BR
	   -0.5f, -0.5f, 0.0f,    // BL
	   -0.5f,  0.5f, 0.0f     // TL
	
	};

	GLuint indices[] = 
	{
		0, 1, 3, 
		1, 2, 3
	
	};

	GLfloat greenColor[] =
	{
	    0.0f, 1.0f, 0.0f,
		0.0f, 1.0f, 0.0f,
		0.0f, 1.0f, 0.0f,
		0.0f, 1.0f, 0.0f
	};

	GLuint shaderProgram = compile_shader();

	GLuint VAO1;
	glGenVertexArrays(1, &VAO1);
	glBindVertexArray(VAO1);

		GLuint VBO1;	
		glGenBuffers(1, &VBO1);	
		glBindBuffer(GL_ARRAY_BUFFER, VBO1);
		glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);

		glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), (GLvoid*)0);
		glEnableVertexAttribArray(0);

		GLuint VBO2;	
		glGenBuffers(1, &VBO2);
		glBindBuffer(GL_ARRAY_BUFFER, VBO2);
		glBufferData(GL_ARRAY_BUFFER, sizeof(greenColor), greenColor, GL_STATIC_DRAW);

		glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 0, nullptr);
		glEnableVertexAttribArray(1);

		GLuint EBO1;
		glGenBuffers(1, &EBO1);
		glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO1);
		glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);

	glBindVertexArray(0);	

	while(Window.isOpen())
	{
		Window.clear();

		sf::Event Event;
		while(Window.pollEvent(Event))
		{
			switch(Event.type)
			{
			case sf::Event::Closed:
				Window.close();
				break;

			case sf::Event::KeyPressed:
				if(sf::Keyboard::isKeyPressed(sf::Keyboard::Escape))
					Window.close();
				break;
			}
		
		}
	
		glUseProgram(shaderProgram);
		glBindVertexArray(VAO1);
		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
		glBindVertexArray(0);

		Window.display();
	}

	glDeleteVertexArrays(1, &VAO1);
	glDeleteBuffers(1, &VBO1);
	glDeleteBuffers(1, &VBO2);
	glDeleteBuffers(1, &EBO1);

	system("Pause");
	return 0;
}
liuyang (217)
Maybe it's because you've closed the window before drawing.
Perhaps you could try exit the loop immediately after you close the window? (after Window.close())
JayhawkZombie (738)
You might want to exit immediately after the window closes. OpenGL will still try to render in that closed window even though you've closed it because you're still executing in that while loop.
Student555 (48)
Why does OpenGL still try to render even if the Window has been closed. Do I have to do this everytime I use glDrawElement. I never had this problem with glDrawArray
Last edited on
JayhawkZombie (738)
Have you tried catching the exception and seeing what it says?

It's best to avoid render calls after your window (and thus your rendering context) has been destroyed.
Your rendering context got destroyed when you closed the window. OpenGL can't draw without that.

Here's a good page to look at:
http://www.sfml-dev.org/tutorials/2.0/window-opengl.php



Here we don't use window.isOpen() as the condition of the main loop, because we need the window to remain open until the program ends, so that we still have a valid OpenGL context for the last iteration of the loop and the cleanup code.


That being said, you need to keep the rendering context valid until all rendering calls have been completed and all cleanup code is finished. That page should help you out.
Last edited on
JayhawkZombie (738)
Another thing:

In here:

1
2
 
	if(GLEW_OK != glewInit())
		cout << "Error! Could not initialize Glew" << endl;


If GLEW fails to initialize, there's no reason to continue execution. You can abort your program.
Student555 (48)
It works now, I used boolean expressions to exit out of the loop before a call to glDrawElement is made. 
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
 
			case sf::Event::Closed:
				stop = true;
				Window.close();
				break;
			case sf::Event::KeyPressed:
				if(sf::Keyboard::isKeyPressed(sf::Keyboard::Escape))
				{
					stop = true;
					Window.close();
				}
				break;


			}
		
		}

		if(stop)
			break;
JayhawkZombie (738)
That'll work!

Just make sure you don't make any draw calls after the window got destroyed.

Have fun with OpenGL!
Topic archived. No new replies allowed.