I’m just trying to draw a bunch of lines that make up a “cube”. I can’t for the life of me figure out why this is producing a black screen. The debugger does not break at any point.
I’m sure it’s a problem with my pointers, as I’m only decent at them in regular c++ and in OpenGL it gets even worse.
const char* vertexSource =
"#version 150\n"
"in vec3 position;"
"void main() {"
" gl_Position = vec4(position, 1.0);"
"}";
const char* fragmentSource =
"#version 150\n"
"out vec4 outColor;"
"void main() {"
" outColor = vec4(1.0, 1.0, 1.0, 1.0);"
"}";
int main() {
initializeGLFW();
// Initialize GLEW
glewExperimental = GL_TRUE;
glewInit();
// Create Vertex Array Object
GLuint vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
// Create a Vertex Buffer Object and copy the vertex data to it
GLuint vbo;
glGenBuffers( 1, &vbo );
float vertices[] = {
1.0f, 1.0f, 1.0f, // Vertex 0 (X, Y, Z)
-1.0f, 1.0f, 1.0f, // Vertex 1 (X, Y, Z)
-1.0f, -1.0f, 1.0f, // Vertex 2 (X, Y, Z)
1.0f, -1.0f, 1.0f, // Vertex 3 (X, Y, Z)
1.0f, 1.0f, -1.0f, // Vertex 4 (X, Y, Z)
-1.0f, 1.0f, -1.0f, // Vertex 5 (X, Y, Z)
-1.0f, -1.0f, -1.0f, // Vertex 6 (X, Y, Z)
1.0f, -1.0f, -1.0f // Vertex 7 (X, Y, Z)
};
GLuint indices[] = {
0, 1,
1, 2,
2, 3,
3, 0,
4, 5,
5, 6,
6, 7,
7, 4,
0, 4,
1, 5,
2, 6,
3, 7
};
glBindBuffer( GL_ARRAY_BUFFER, vbo );
glBufferData( GL_ARRAY_BUFFER, sizeof( vertices ), vertices, GL_STATIC_DRAW );
//glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, vbo);
//glBufferData( GL_ELEMENT_ARRAY_BUFFER, sizeof( indices ), indices, GL_STATIC_DRAW );
// Create and compile the vertex shader
GLuint vertexShader = glCreateShader( GL_VERTEX_SHADER );
glShaderSource( vertexShader, 1, &vertexSource, NULL );
glCompileShader( vertexShader );
// Create and compile the fragment shader
GLuint fragmentShader = glCreateShader( GL_FRAGMENT_SHADER );
glShaderSource( fragmentShader, 1, &fragmentSource, NULL );
glCompileShader( fragmentShader );
// Link the vertex and fragment shader into a shader program
GLuint shaderProgram = glCreateProgram();
glAttachShader( shaderProgram, vertexShader );
glAttachShader( shaderProgram, fragmentShader );
glBindFragDataLocation( shaderProgram, 0, "outColor" );
glLinkProgram (shaderProgram);
glUseProgram( shaderProgram);
// Specify the layout of the vertex data
GLint posAttrib = glGetAttribLocation( shaderProgram, "position" );
glEnableVertexAttribArray( posAttrib );
glVertexAttribPointer( posAttrib, 3, GL_FLOAT, GL_FALSE, 0, 0 );
// Main loop
while(glfwGetWindowParam(GLFW_OPENED)) {
// Clear the screen to black
glClearColor( 0.0f, 0.0f, 0.0f, 1.0f );
glClear( GL_COLOR_BUFFER_BIT );
// Draw lines from 2 vertices
glDrawElements(GL_LINES, sizeof(indices), GL_UNSIGNED_INT, indices );
// Swap buffers
glfwSwapBuffers();
}
// Clean up
glDeleteProgram( shaderProgram );
glDeleteShader( fragmentShader );
glDeleteShader( vertexShader );
//glDeleteBuffers( 1, &ebo );
glDeleteBuffers( 1, &vbo );
glDeleteVertexArrays( 1, &vao );
glfwTerminate();
exit( EXIT_SUCCESS );
}
EDIT: Full code trying the first answer’s recommendation. Still blank.
#define GLEW_STATIC
#include <GL/glew.h>
#include <GL/glfw.h>
#include <iostream>
#pragma comment( lib, "glfw.lib")
#pragma comment( lib, "opengl32.lib")
#pragma comment( lib, "glew32s.lib")
const char* vertexSource =
"#version 150\n"
"in vec3 position;"
"void main() {"
" gl_Position = vec4(position.x, position.y, position.z - 0.9, 1.0);"
"}";
const char* fragmentSource =
"#version 150\n"
"out vec4 outColor;"
"void main() {"
" outColor = vec4(1.0, 1.0, 1.0, 1.0);"
"}";
void initializeGLFW();
int main() {
initializeGLFW();
// Initialize GLEW
glewExperimental = GL_TRUE;
glewInit();
// Create Vertex Array Object
GLuint vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
// Create a Vertex Buffer Object and copy the vertex data to it
GLuint vbo;
glGenBuffers( 1, &vbo );
float vertices[] = {
1.0f, 1.0f, 1.0f, // Vertex 0 (X, Y, Z)
-1.0f, 1.0f, 1.0f, // Vertex 1 (X, Y, Z)
-1.0f, -1.0f, 1.0f, // Vertex 2 (X, Y, Z)
1.0f, -1.0f, 1.0f, // Vertex 3 (X, Y, Z)
1.0f, 1.0f, -1.0f, // Vertex 4 (X, Y, Z)
-1.0f, 1.0f, -1.0f, // Vertex 5 (X, Y, Z)
-1.0f, -1.0f, -1.0f, // Vertex 6 (X, Y, Z)
1.0f, -1.0f, -1.0f // Vertex 7 (X, Y, Z)
};
size_t vertCount = sizeof( vertices ) / sizeof( float );
for( size_t i = 0; i < vertCount; ++i ) {
vertices[i] /= 2.0f;
}
GLubyte indices[] = {
0, 1,
1, 2,
2, 3,
3, 0,
4, 5,
5, 6,
6, 7,
7, 4,
0, 4,
1, 5,
2, 6,
3, 7
};
glBindBuffer( GL_ARRAY_BUFFER, vbo );
//glBindBuffer( GL_ELEMENT_ARRAY_BUFFER, vbo);
glBufferData( GL_ARRAY_BUFFER, sizeof( vertices ), vertices, GL_STATIC_DRAW );
// Create and compile the vertex shader
GLuint vertexShader = glCreateShader( GL_VERTEX_SHADER );
glShaderSource( vertexShader, 1, &vertexSource, NULL );
glCompileShader( vertexShader );
// Create and compile the fragment shader
GLuint fragmentShader = glCreateShader( GL_FRAGMENT_SHADER );
glShaderSource( fragmentShader, 1, &fragmentSource, NULL );
glCompileShader( fragmentShader );
// Link the vertex and fragment shader into a shader program
GLuint shaderProgram = glCreateProgram();
glAttachShader( shaderProgram, vertexShader );
glAttachShader( shaderProgram, fragmentShader );
glBindFragDataLocation( shaderProgram, 0, "outColor" );
glLinkProgram (shaderProgram);
glUseProgram( shaderProgram);
// Specify the layout of the vertex data
GLint posAttrib = glGetAttribLocation( shaderProgram, "position" );
glEnableVertexAttribArray( posAttrib );
glVertexAttribPointer( posAttrib, 3, GL_FLOAT, GL_FALSE, 0, vertices );
// Main loop
while(glfwGetWindowParam(GLFW_OPENED)) {
// Clear the screen to black
glClearColor( 0.0f, 0.0f, 0.0f, 1.0f );
glClear( GL_COLOR_BUFFER_BIT );
// Draw lines from 2 vertices
glDrawElements(GL_LINES, 24, GL_UNSIGNED_BYTE, indices);
// Swap buffers
glfwSwapBuffers();
}
// Clean up
glDeleteProgram( shaderProgram );
glDeleteShader( fragmentShader );
glDeleteShader( vertexShader );
//glDeleteBuffers( 1, &ebo );
glDeleteBuffers( 1, &vbo );
glDeleteVertexArrays( 1, &vao );
glfwTerminate();
exit( EXIT_SUCCESS );
}
void initializeGLFW() {
glfwInit();
glfwOpenWindowHint( GLFW_OPENGL_VERSION_MAJOR, 3 );
glfwOpenWindowHint( GLFW_OPENGL_VERSION_MINOR, 2 );
glfwOpenWindowHint( GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE );
glfwOpenWindowHint( GLFW_WINDOW_NO_RESIZE, GL_TRUE );
glfwOpenWindow( 800, 600, 0, 0, 0, 0, 0, 0, GLFW_WINDOW );
glfwSetWindowTitle( "OpenGL" );
}
The “default” projection is essentially
glOrtho(-1, 1, -1, 1, -1, 1)with the camera at(0,0,0)looking down the -Z axis.Move the camera back:
And make your object smaller:
Complete: