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lukaslukas
11-27-2017, 05:59 PM
Hey guys. I mixed two "tutorials" together to get the advantage of both, but this doesn't work for me.

It's Glutdualwindow.c by Eric Stringer 2002 to get 2 Windows. And [URL="https://en.wikibooks.org/wiki/OpenGL_Programming/Modern_OpenGL_Tutorial_06"]. Since I am not very experienced, I am really stuck now. :(
Somewhere I seem to crash the program by overwriting a buffer or something.

Basically I just want to put the texture stuff into the second window, while void display_1(void)
remains unchanged.

Both tutorials alone work proper. :(


// Glutdualwindow.c
// By Eric Stringer 2002
// Simple examples of OpenGL and Glut usage.
// Keyboard input
// 'v' = view ortho/perspective
// 'l' = lighting on/off


//#include <windows.h> // This header file will be needed for some windows compilers
//#include <GL/gl.h> // gl.h and glu.h also maybe needed for some compilers
//#include <GL/glu.h>
//USE FREEGLUT//#include <GL/glut.h> // glut (gl utility toolkit) basic windows functions, keyboard, mouse.
#include <stdio.h> // standard (I/O library)
#include <stdlib.h> // standard library (set of standard C functions
#include <math.h> // Math library (Higher math functions )
#include <cstring>

/* Use glew.h instead of gl.h to get all the GL prototypes declared */
#include <GL/glew.h>
/* Using the GLUT library for the base windowing setup */
#include <GL/freeglut.h>
/* GLM */
// #define GLM_MESSAGES
#define GLM_FORCE_RADIANS
#include <glm/glm.hpp>
#include <glm/gtc/matrix_transform.hpp>
#include <glm/gtc/type_ptr.hpp>
#include "shader_utils.h"

#include "res_texture.c"


int screen_width=800, screen_height=600;
GLuint vbo_cube_vertices, vbo_cube_texcoords;
GLuint ibo_cube_elements;
GLuint program;
GLuint texture_id;
GLint attribute_coord3d, attribute_texcoord;
GLint uniform_mvp, uniform_mytexture;


// lighting
GLfloat LightAmbient[]= { 0.2f, 0.2f, 0.2f, 1.0f };
GLfloat LightDiffuse[]= { 0.5f, 0.5f, 0.5f, 1.0f };
GLfloat LightPosition[]= { 5.0f, 5.0f, -10.0f, 1.0f };
GLfloat mat_specular[] = { 0.2, 0.2, 0.2, 1.0 };

int window_1, window_2;

static int view_state = 0, light_state = 0;

int spin;

int shape;



int init_resources()
{
GLfloat cube_vertices[] = {
// front
-1.5, -0.8, 0.8,
1.5, -0.8, 0.8,
1.5, 0.8, 0.8,
-1.5, 0.8, 0.8,
// top
-1.5, 0.8, 0.8,
1.5, 0.8, 0.8,
1.5, 0.8, -0.8,
-1.5, 0.8, -0.8,
// back
1.5, -0.8, -0.8,
-1.5, -0.8, -0.8,
-1.5, 0.8, -0.8,
1.5, 0.8, -0.8,
// bottom
-1.5, -0.8, -0.8,
1.5, -0.8, -0.8,
1.5, -0.8, 0.8,
-1.5, -0.8, 0.8,
// left
-1.5, -0.8, -0.8,
-1.5, -0.8, 0.8,
-1.5, 0.8, 0.8,
-1.5, 0.8, -0.8,
// right
1.4, -0.8, 0.8,
1.4, -0.8, -0.8,
1.4, 0.8, -0.8,
1.4, 0.8, 0.8,
};
glGenBuffers(1, &vbo_cube_vertices);
glBindBuffer(GL_ARRAY_BUFFER, vbo_cube_vertices);
glBufferData(GL_ARRAY_BUFFER, sizeof(cube_vertices), cube_vertices, GL_STATIC_DRAW);

GLfloat cube_texcoords[2*4*6] = {
// front
0.0, 0.0,
1.0, 0.0,
1.0, 1.0,
0.0, 1.0,
};
for (int i = 1; i < 6; i++)
memcpy(&cube_texcoords[i*4*2], &cube_texcoords[0], 2*4*sizeof(GLfloat));
glGenBuffers(1, &vbo_cube_texcoords);
glBindBuffer(GL_ARRAY_BUFFER, vbo_cube_texcoords);
glBufferData(GL_ARRAY_BUFFER, sizeof(cube_texcoords), cube_texcoords, GL_STATIC_DRAW);

GLushort cube_elements[] = {
// front
0, 1, 2,
2, 3, 0,
// top
4, 5, 6,
6, 7, 4,
// back
8, 9, 10,
10, 11, 8,
// bottom
12, 13, 14,
14, 15, 12,
// left
16, 17, 18,
18, 19, 16,
// right
20, 21, 22,
22, 23, 20,
};
glGenBuffers(1, &ibo_cube_elements);
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo_cube_elements);
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(cube_elements), cube_elements, GL_STATIC_DRAW);

glGenTextures(1, &texture_id);
glBindTexture(GL_TEXTURE_2D, texture_id);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexImage2D(GL_TEXTURE_2D, // target
0, // level, 0 = base, no minimap,
GL_RGB, // internalformat
res_texture.width, // width
res_texture.height, // height
0, // border, always 0 in OpenGL ES
GL_RGB, // format
GL_UNSIGNED_BYTE, // type
res_texture.pixel_data);

GLint link_ok = GL_FALSE;

GLuint vs, fs;
if ((vs = create_shader("cube.v.glsl", GL_VERTEX_SHADER)) == 0) return 0;
if ((fs = create_shader("cube.f.glsl", GL_FRAGMENT_SHADER)) == 0) return 0;

program = glCreateProgram();
glAttachShader(program, vs);
glAttachShader(program, fs);
glLinkProgram(program);
glGetProgramiv(program, GL_LINK_STATUS, &link_ok);
if (!link_ok) {
fprintf(stderr, "glLinkProgram:");
print_log(program);
return 0;
}

const char* attribute_name;
attribute_name = "coord3d";
attribute_coord3d = glGetAttribLocation(program, attribute_name);
if (attribute_coord3d == -1) {
fprintf(stderr, "Could not bind attribute %s\n", attribute_name);
return 0;
}
attribute_name = "texcoord";
attribute_texcoord = glGetAttribLocation(program, attribute_name);
if (attribute_texcoord == -1) {
fprintf(stderr, "Could not bind attribute %s\n", attribute_name);
return 0;
}
const char* uniform_name;
uniform_name = "mvp";
uniform_mvp = glGetUniformLocation(program, uniform_name);
if (uniform_mvp == -1) {
fprintf(stderr, "Could not bind uniform %s\n", uniform_name);
return 0;
}
uniform_name = "mytexture";
uniform_mytexture = glGetUniformLocation(program, uniform_name);
if (uniform_mytexture == -1) {
fprintf(stderr, "Could not bind uniform %s\n", uniform_name);
return 0;
}

return 1;
}



// I use this to put text on the screen
void Sprint( int x, int y, char *st)
{
int l,i;

l=strlen( st ); // see how many characters are in text string.
glRasterPos2i( x, y); // location to start printing text
for( i=0; i < l; i++) // loop until i is greater then l
{
glutBitmapCharacter(GLUT_BITMAP_TIMES_ROMAN_24, st[i]); // Print a character on the screen
}

}


// This creates the spinning of the cube.
static void TimeEvent(int te)
{

spin++; // increase cube rotation by 1
if (spin > 360) spin = 0; // if over 360 degress, start back at zero.

glutSetWindow( window_1 );
glutPostRedisplay(); // Update screen with new rotation data

glutSetWindow( window_2 );
glutPostRedisplay(); // Update screen with new rotation data

glutTimerFunc( 100, TimeEvent, 1); // Reset our timmer.
}


// Setup our Opengl world, called once at startup.
void init(void)
{


glClearColor (0.0, 0.0, 0.0, 0.0); // When screen cleared, use black.
glShadeModel (GL_SMOOTH); // How the object color will be rendered smooth or flat
glEnable(GL_DEPTH_TEST); // Check depth when rendering
// Lighting is added to scene
glLightfv(GL_LIGHT1 ,GL_AMBIENT, LightAmbient);
glLightfv(GL_LIGHT1 ,GL_DIFFUSE, LightDiffuse);
glLightfv(GL_LIGHT1 ,GL_POSITION, LightPosition);
glEnable(GL_LIGHTING); // Turn on lighting
glEnable(GL_LIGHT1); // Turn on light 1


}


// Draw our world
void display_1(void)
{
char *p;

glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //Clear the screen

glMatrixMode (GL_PROJECTION); // Tell opengl that we are doing project matrix work
glLoadIdentity(); // Clear the matrix
glOrtho(-8.0, 8.0, -8.0, 8.0, 0.0, 30.0); // Setup an Ortho view
glMatrixMode(GL_MODELVIEW); // Tell opengl that we are doing model matrix work. (drawing)
glLoadIdentity(); // Clear the model matrix


glColor3f(1.0, 1.0, 1.0);
if (shape == 0) Sprint(-3, -7 ,"Solid Cube");
if (shape == 1) Sprint(-3, -7 ,"Solid Cone");
if (shape == 2) Sprint(-3, -7 ,"Solid Sphere");
if (shape == 3) Sprint(-3, -7 ,"Solid Torus");
if (shape == 4) Sprint(-3, -7 ,"Solid Dodecahedron");
if (shape == 5) Sprint(-3, -7 ,"Solid Octahedron");
if (shape == 6) Sprint(-3, -7 ,"Solid Tetrahedron");
if (shape == 7) Sprint(-3, -7 ,"Solid Icosahedron");
if (shape == 8) Sprint(-3, -7 ,"Solid Teapot");

// Setup view, and print view state on screen
if (view_state == 1)
{
glColor3f( 1.0, 1.0, 1.0);
Sprint(-2, 4, "Perspective view");
glMatrixMode (GL_PROJECTION);
glLoadIdentity();
gluPerspective(60, 1, 1, 30);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
}else
{
glColor3f( 1.0, 1.0, 1.0);
Sprint(-2, 4, "Ortho view");
}

glColor3f( 0.0, 0.0, 1.0); // Cube color

// Lighting on/off
if (light_state == 1)
{
glDisable(GL_LIGHTING); // Turn off lighting
glDisable(GL_COLOR_MATERIAL); // Turn off material, which needs lighting to work
}else
{
glEnable(GL_LIGHTING); // Turn on lighting
glEnable(GL_COLOR_MATERIAL); // Turn on material settings
glColorMaterial(GL_FRONT, GL_AMBIENT);
glColor4f(0.65, 0.65, 0.65, 0.4);
glColorMaterial(GL_FRONT, GL_EMISSION);
glColor4f(0.10, 0.10, 0.10, 0.0);
glColorMaterial(GL_FRONT, GL_SPECULAR);
glColor4f(0.5, 0.5, 0.5, 0.4);
glColorMaterial(GL_FRONT, GL_DIFFUSE);
glColor4f(0.85, 0.85, 0.85, 0.4);
}

gluLookAt( 0, 0, 20, 0, 0, 0, 0, 1, 0);

//glRotatef( 45, 1.0, 1.0, 0.0); // rotate cube
glRotatef( spin++, 1.0, 1.0, 1.0); // spin cube

if (shape == 0) glutSolidCube(10); // Draw a cube
if (shape == 1) glutSolidCone(5,10, 16,16); // Draw a Cone
if (shape == 2) glutSolidSphere(5, 16,16 ); // Draw a Sphere
if (shape == 3) glutSolidTorus( 2.5, 5, 16, 16);
if (shape == 4)
{
glScalef( 3.5, 3.5, 3.5);
glutSolidDodecahedron();
}

if (shape == 5)
{
glScalef( 5.0, 5.0, 5.0);
glutSolidOctahedron();
}
if (shape == 6)
{
glScalef( 5.0, 5.0, 5.0);
glutSolidTetrahedron();
}

if (shape == 7)
{
glScalef( 5.0, 5.0, 5.0);
glutSolidIcosahedron();
}
if (shape == 8) glutSolidTeapot( 5 );

glutSwapBuffers();
}

void display_2(void)
{
glClear (GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); //Clear the screen

glMatrixMode (GL_PROJECTION); // Tell opengl that we are doing project matrix work
glLoadIdentity(); // Clear the matrix
glOrtho(-8.0, 8.0, -8.0, 8.0, 0.0, 30.0); // Setup an Ortho view
glMatrixMode(GL_MODELVIEW); // Tell opengl that we are doing model matrix work. (drawing)
glLoadIdentity(); // Clear the model matrix

glUseProgram(program);

glActiveTexture(GL_TEXTURE0);
glBindTexture(GL_TEXTURE_2D, texture_id);
glUniform1i(uniform_mytexture, /*GL_TEXTURE*/0);

glEnableVertexAttribArray(attribute_coord3d);
// Describe our vertices array to OpenGL (it can't guess its format automatically)
glBindBuffer(GL_ARRAY_BUFFER, vbo_cube_vertices);
glVertexAttribPointer(
attribute_coord3d, // attribute
3, // number of elements per vertex, here (x,y,z)
GL_FLOAT, // the type of each element
GL_FALSE, // take our values as-is
0, // no extra data between each position
0 // offset of first element
);

glEnableVertexAttribArray(attribute_texcoord);
glBindBuffer(GL_ARRAY_BUFFER, vbo_cube_texcoords);
glVertexAttribPointer(
attribute_texcoord, // attribute
2, // number of elements per vertex, here (x,y)
GL_FLOAT, // the type of each element
GL_FALSE, // take our values as-is
0, // no extra data between each position
0 // offset of first element
);

/* Push each element in buffer_vertices to the vertex shader */
glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ibo_cube_elements);
int size; glGetBufferParameteriv(GL_ELEMENT_ARRAY_BUFFER, GL_BUFFER_SIZE, &size);
glDrawElements(GL_TRIANGLES, size/sizeof(GLushort), GL_UNSIGNED_SHORT, 0);

glDisableVertexAttribArray(attribute_coord3d);
glDisableVertexAttribArray(attribute_texcoord);
glutSwapBuffers();
}


// This is called when the window has been resized.
void reshape_1 (int w, int h)
{
glViewport (0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity ();
}

// This is called when the window has been resized.
void reshape_2 (int w, int h)
{
glViewport (0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode (GL_PROJECTION);
glLoadIdentity ();
}

// Read the keyboard
void keyboard (unsigned char key, int x, int y)
{
switch (key)
{

case 'v':
case 'V':
view_state = abs(view_state -1);
break;
case 'l':
case 'L':
light_state = abs(light_state -1);
break;
case 's':
case 'S':
shape++;
break;
case 27:
exit(0); // exit program when [ESC] key presseed
break;
default:
break;
}

if (shape > 8) shape = 0;

}


// Main program
int main(int argc, char** argv)
{
glutInit(&argc, argv);
glutInitDisplayMode (GLUT_DOUBLE | GLUT_RGB);
glutInitWindowSize (500, 500);
glutInitWindowPosition (10, 10);
glutTimerFunc( 10, TimeEvent, 1);
window_1 = glutCreateWindow (argv[0]);
glutSetWindowTitle("GlutWindow 1");
init ();
glutDisplayFunc(display_1);
glutReshapeFunc(reshape_1);
glutKeyboardFunc(keyboard);

window_2 = glutCreateWindow (argv[0]);
glutSetWindowTitle("GlutWindow 2");
init ();
glutDisplayFunc(display_2);
glutReshapeFunc(reshape_2);
glutMainLoop();
return 0;
}

lukaslukas
11-28-2017, 03:44 AM
I know that this probably is a frequently seen issue. Some noob, that does not know how to read the documents. But personally, I don't want to become a game developer. I am just impressed by opengl. For someone plotting a complete game scene this must be easy.

But if you just start to understand how all this buffering and rendering works, than there is just to much documentation out there. and even if i read about something I have to declare or to clear or some setting to make than it's really difficult to understand when this has to be done.

If we use the ready tog functions like void
glutSolidCube(GLdouble size); etc. ...

it works, but why?