Cube drawn with OpenGL lacks depth/perspective?
c++, glfw, opengl
Solution
- You never set a (meaningful) projection matrix.
- Abuse not the projection matrix stack.
- Don't set your matrices in `drawCube()`, single responsibility principle and all that.
- Set your viewport before trying to draw.
- C++ has `c`-prefixed versions (`stdio.h` -> `cstdio`) of the C headers. Use those instead.
All together:
#include <GL/glew.h>
#include <GLFW/glfw3.h>
#include <cstdio>
void controls(GLFWwindow* window, int key, int scancode, int action, int mods)
{
if(action == GLFW_PRESS)
if(key == GLFW_KEY_ESCAPE)
glfwSetWindowShouldClose(window, GL_TRUE);
}
GLFWwindow* initWindow(const int resX, const int resY)
{
if(!glfwInit())
{
fprintf(stderr, "Failed to initialize GLFW\n");
return NULL;
}
glfwWindowHint(GLFW_SAMPLES, 4); // 4x antialiasing
// Open a window and create its OpenGL context
GLFWwindow* window = glfwCreateWindow(resX, resY, "TEST", NULL, NULL);
if(window == NULL)
{
fprintf(stderr, "Failed to open GLFW window.\n");
glfwTerminate();
return NULL;
}
glfwMakeContextCurrent(window);
glfwSetKeyCallback(window, controls);
// Get info of GPU and supported OpenGL version
printf("Renderer: %s\n", glGetString(GL_RENDERER));
printf("OpenGL version supported %s\n", glGetString(GL_VERSION));
glEnable(GL_DEPTH_TEST); // Depth Testing
glDepthFunc(GL_LEQUAL);
glDisable(GL_CULL_FACE);
glCullFace(GL_BACK);
return window;
}
void drawCube()
{
GLfloat vertices[] =
{
-1, -1, -1, -1, -1, 1, -1, 1, 1, -1, 1, -1,
1, -1, -1, 1, -1, 1, 1, 1, 1, 1, 1, -1,
-1, -1, -1, -1, -1, 1, 1, -1, 1, 1, -1, -1,
-1, 1, -1, -1, 1, 1, 1, 1, 1, 1, 1, -1,
-1, -1, -1, -1, 1, -1, 1, 1, -1, 1, -1, -1,
-1, -1, 1, -1, 1, 1, 1, 1, 1, 1, -1, 1
};
GLfloat colors[] =
{
0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 1, 0,
1, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0,
0, 0, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0,
0, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0,
0, 0, 0, 0, 1, 0, 1, 1, 0, 1, 0, 0,
0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1
};
static float alpha = 0;
//attempt to rotate cube
glRotatef(alpha, 0, 1, 0);
/* We have a color array and a vertex array */
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glVertexPointer(3, GL_FLOAT, 0, vertices);
glColorPointer(3, GL_FLOAT, 0, colors);
/* Send data : 24 vertices */
glDrawArrays(GL_QUADS, 0, 24);
/* Cleanup states */
glDisableClientState(GL_COLOR_ARRAY);
glDisableClientState(GL_VERTEX_ARRAY);
alpha += 1;
}
void display( GLFWwindow* window )
{
while(!glfwWindowShouldClose(window))
{
// Scale to window size
GLint windowWidth, windowHeight;
glfwGetWindowSize(window, &windowWidth, &windowHeight);
glViewport(0, 0, windowWidth, windowHeight);
// Draw stuff
glClearColor(0.0, 0.8, 0.3, 1.0);
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glMatrixMode(GL_PROJECTION_MATRIX);
glLoadIdentity();
gluPerspective( 60, (double)windowWidth / (double)windowHeight, 0.1, 100 );
glMatrixMode(GL_MODELVIEW_MATRIX);
glTranslatef(0,0,-5);
drawCube();
// Update Screen
glfwSwapBuffers(window);
// Check for any input, or window movement
glfwPollEvents();
}
}
int main(int argc, char** argv)
{
GLFWwindow* window = initWindow(1024, 620);
if( NULL != window )
{
display( window );
}
glfwDestroyWindow(window);
glfwTerminate();
return 0;
}
Problem
I am trying to draw a simple cube in OpenGL and GLFW. In the code below, I can draw the cube, but it just appears as a simple rectangle. What is happening here? ``` #if defined(_WIN32) || defined(_WIN64) #include <windows.h> #endif #include <stdio.h> #include <stdlib.h> #include <iostream> #include <fstream> #define GLEW_STATIC #include <GL/glew.h> #include <GL/gl.h> #include <GLFW/glfw3.h> const char* gameTitle = "TEST"; GLFWwindow* window; GLfloat vertices[] = { -1, -1, -1, -1, -1, 1, -1, 1, 1, -1, 1, -1, 1, -1, -1, 1, -1, 1, 1, 1, 1, 1, 1, -1, -1, -1, -1, -1, -1, 1, 1, -1, 1, 1, -1, -1, -1, 1, -1, -1, 1, 1, 1, 1, 1, 1, 1, -1, -1, -1, -1, -1, 1, -1, 1, 1, -1, 1, -1, -1, -1, -1, 1, -1, 1, 1, 1, 1, 1, 1, -1, 1 }; GLfloat colors[] = { 0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 1, 0, 1, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 0, 1, 1, 0, 1, 1, 0, 0, 0, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 0, 0, 0, 0, 0, 1, 0, 1, 1, 0, 1, 0, 0, 0, 0, 1, 0, 1, 1, 1, 1, 1, 1, 0, 1 }; static void controls(GLFWwindow* window, int key, int scancode, int action, int mods) { if(action == GLFW_PRESS) if(key == GLFW_KEY_ESCAPE) glfwSetWindowShouldClose(window, GL_TRUE); } bool initWindow(const int resX, const int resY) { if(!glfwInit()) { fprintf(stderr, "Failed to initialize GLFW\n"); return false; } glfwWindowHint(GLFW_SAMPLES, 4); // 4x antialiasing // Open a window and create its OpenGL context window = glfwCreateWindow(resX, resY, gameTitle, NULL, NULL); if(window == NULL) { fprintf(stderr, "Failed to open GLFW window.\n"); glfwTerminate(); return false; } glfwMakeContextCurrent(window); glfwSetKeyCallback(window, controls); // Get info of GPU and supported OpenGL version printf("Renderer: %s\n", glGetString(GL_RENDERER)); printf("OpenGL version supported %s\n", glGetString(GL_VERSION)); glEnable(GL_DEPTH_TEST); // Depth Testing glDepthFunc(GL_LEQUAL); glDisable(GL_CULL_FACE); glCullFace(GL_BACK); return true; } static void drawCube() { static float alpha = 0; glMatrixMode(GL_PROJECTION_MATRIX); glLoadIdentity(); glTranslatef(0,0,-2); glMatrixMode(GL_MODELVIEW_MATRIX); //attempt to rotate cube //glRotatef(alpha, 1, 0, 0); /* We have a color array and a vertex array */ glEnableClientState(GL_VERTEX_ARRAY); glEnableClientState(GL_COLOR_ARRAY); glVertexPointer(3, GL_FLOAT, 0, vertices); glColorPointer(3, GL_FLOAT, 0, colors); /* Send data : 24 vertices */ glDrawArrays(GL_QUADS, 0, 24); /* Cleanup states */ glDisableClientState(GL_COLOR_ARRAY); glDisableClientState(GL_VERTEX_ARRAY); alpha += 0.1; } static void display() { glClearColor(0.0, 0.8, 0.3, 1.0); while(!glfwWindowShouldClose(window)) { // Draw stuff glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); drawCube(); // Update Screen //glFlush(); glfwSwapBuffers(window); // Check for any input, or window movement glfwPollEvents(); // Scale to window size GLint windowWidth, windowHeight; glfwGetWindowSize(window, &windowWidth, &windowHeight); glViewport(0, 0, windowWidth, windowHeight); } } int main(int argc, char** argv) { if(initWindow(1024, 620)) { display(); } printf("Goodbye!\n"); glfwDestroyWindow(window); glfwTerminate(); return 0; } ``` I've tried "glTransformf(0,0,-10);", but if I do anything less than -2, than the cube disappears. at -2, the front face side appears. at the default position of 0, I can see the back side of the cube. Also, when I try to rotate it, all that shows up is a rectangle moving from the top of the window, to the bottom. Seems very odd. Why is the program is behaving this way?