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Back to Graphics and GPU Programming

display window black, no skymap

Started by
3 comments, last by nick2price 15 years, 5 months ago
I followed a tutorial to create a skymap. The problem was that the tutorial used glaux and created the window not through a main, so i had to change these couple of things. Everything compiles now but for some reason the display screen is just black. Can someone look at the code to see if there is a logical reason for this. Thanks very much skybox.cpp 

#include "stdafx.h"
#include <GL/glut.h>
#include <windows.h>
#include <stdio.h>  //for file access							
#include <gl\gl.h>													
#include "skybox.h"
#include "glbmp.h"


GLuint skybox::LoadTexture(const char * bitmap_file)
{
   GLuint texture = 0; //OpenGL texture to create and return
   glbmp_t bitmap;     //object to fill with data from glbmp
 
   
   if(!glbmp_LoadBitmap(bitmap_file, 0, &bitmap))
   {
      fprintf(stderr, "Error loading bitmap file: %s\n", bitmap_file);
   }
 
   //generate and bind the OpenGL texture
   glGenTextures(1, &texture);
   glBindTexture(GL_TEXTURE_2D, texture);
 
   //copy data from bitmap into texture
   glTexImage2D(GL_TEXTURE_2D, 0, 3, bitmap.width, bitmap.height,
                0, GL_RGB, GL_UNSIGNED_BYTE, bitmap.rgb_data);
 
   //set up texture filtering
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
 
   //free the bitmap
   glbmp_FreeBitmap(&bitmap);
 
   return texture;
}
 


void skybox::Init() {

	OFFSET = 1/512.0; //set offset value for skybox

	rot_x = 0.0; rot_y = 0.0;

    GLuint tex1;
	GLuint tex2;
	GLuint tex3;
	GLuint tex4;
	GLuint tex5;
	GLuint tex6;

	tex1 = LoadTexture("images/left1.bmp");
	tex2 = LoadTexture("images/front1.bmp");
	tex3 = LoadTexture("images/right1.bmp");
	tex4 = LoadTexture("images/back1.bmp");
	tex5 = LoadTexture("images/down1.bmp");
	tex6 = LoadTexture("images/up1.bmp");

}


//This is where the magic happens
void skybox::draw() {

		glPushMatrix();
	glRotated(rot_x, 1.0, 0.0, 0.0);	//Rotate around the x axis
	glRotated(rot_y, 0.0, 1.0, 0.0);	//Rotate around the y axis

	glColor3f(1.0f,1.0f,1.0f);			//Set colour to White
	glEnable(GL_TEXTURE_2D);			//Enable texture mapping
	glDisable (GL_DEPTH_TEST);			//Disable depth testing

		//before you can use a texture you have to bind it
		glBindTexture(GL_TEXTURE_2D, texture[0 + text_offset]);

		glBegin (GL_QUADS);	
		
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET,0.0 + OFFSET);	glVertex3d (-10.0,-10.0,10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET,0.0 + OFFSET);	glVertex3d (-10.0,-10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET,1.0 - OFFSET);	glVertex3d (-10.0,10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET,1.0 - OFFSET);	glVertex3d (-10.0,10.0,10.0);

		glEnd ();				

		glBindTexture(GL_TEXTURE_2D, texture[1 + text_offset]);
		glBegin (GL_QUADS);
		
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET,0.0 + OFFSET);	glVertex3d (-10.0,-10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET,0.0 + OFFSET);	glVertex3d (10.0,-10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET,1.0 - OFFSET);	glVertex3d (10.0,10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET,1.0 - OFFSET);	glVertex3d (-10.0,10.0,-10.0);
		glEnd ();

		glBindTexture(GL_TEXTURE_2D, texture[2 + text_offset]);
		glBegin (GL_QUADS);
		
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,0.0 + OFFSET); glVertex3d (10.0,-10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,0.0 + OFFSET); glVertex3d (10.0,-10.0,10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,1.0 - OFFSET); glVertex3d (10.0,10.0,10.0);
				glNormal3d (0.0,0.0,10.0); glTexCoord2d (0.0 + OFFSET ,1.0 - OFFSET); glVertex3d (10.0,10.0,-10.0);

		glEnd ();

		glBindTexture(GL_TEXTURE_2D, texture[3 + text_offset]);	
		glBegin (GL_QUADS);
			
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,0.0 + OFFSET); glVertex3d (10.0,-10.0,10.0);
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,0.0 + OFFSET); glVertex3d (-10.0,-10.0,10.0);
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,1.0 - OFFSET); glVertex3d (-10.0,10.0,10.0);
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,1.0 - OFFSET); glVertex3d (10.0,10.0,10.0);
		
		glEnd ();

		glBindTexture(GL_TEXTURE_2D, texture[4 + text_offset]);	
		glBegin (GL_QUADS);
			
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,0.0 + OFFSET); glVertex3d (-10.0,-10.0,10.0);
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,0.0 + OFFSET); glVertex3d (10.0,-10.0,10.0);
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,1.0 - OFFSET); glVertex3d (10.0,-10.0,-10.0);
			glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,1.0 - OFFSET); glVertex3d (-10.0,-10.0,-10.0);
		
		glEnd ();

		glBindTexture(GL_TEXTURE_2D, texture[5 + text_offset]);
		glBegin (GL_QUADS);
		
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,0.0 + OFFSET); glVertex3d (-10.0,10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,0.0 + OFFSET); glVertex3d (10.0,10.0,-10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,1.0 - OFFSET); glVertex3d (10.0,10.0,10.0);
				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,1.0 - OFFSET); glVertex3d (-10.0,10.0,10.0);
				
		glEnd ();

	//Re-Enable the depth test
	glEnable(GL_DEPTH_TEST);
	//disable texture mapping
	glDisable(GL_TEXTURE_2D);
	glPopMatrix();
	

}
skybox.h 

#define MAX_TEXTURES 24

class skybox {
public:  //just make everything public than you don't have to worry about access

	skybox() { } //constructor

	GLuint LoadTexture(const char * bitmap_file);
	void Init();
	void draw();


	GLuint	texture[MAX_TEXTURES];

	//used to correct the edges of the skybox overlap
	//try setting this to 0.0 in the Init() and you will see the seams of the textures
	double	OFFSET,	rot_x, rot_y;
	long	text_offset;
};
main.cpp 

#include "stdafx.h"
#include <GL/glut.h>
#include <windows.h>
#include <stdio.h>  //for file access							
#include <gl\gl.h>													
#include "skybox.h"
#include "glbmp.h"

int screen_width=800;
int screen_height=600;

skybox		aSkyBox;

GLvoid ReSizeGLScene(GLsizei width, GLsizei height) {

	if (height<=0) { height=1; }

	glViewport(0,0,width,height);

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();

	gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);

	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
}

int InitGL(GLvoid) {
	
	glEnable(GL_TEXTURE_2D);
	glShadeModel(GL_SMOOTH);							//Try GL_FLAT to see the difference
	glClearColor(0.0f, 0.0f, 0.0f, 1.0f);				//Background colour
	glClearDepth(1.0f);
	glEnable(GL_DEPTH_TEST);							//Enables depth testing
	glDepthFunc(GL_LEQUAL);								//Specifies how Depth testing is done
	glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);	//Affects quality of colour and texture interpolation
	glFrontFace (GL_CCW);								//Specifies that the front of a face is defined 
														//in a Counter Clockwise manner
	glCullFace(GL_BACK);								//Specifies that the back of faces are not shown
														//so OpenGL does not need to draw things twice
	glEnable(GL_CULL_FACE);								//Enables culling of faces


	aSkyBox.Init();			//Initalize the Skybox


	return TRUE;
}

void DrawGLScene(GLvoid) {

	glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
	glLoadIdentity();

	aSkyBox.draw();
	glutSwapBuffers(); 
 
}

int main(int argc, char **argv)
{
    glutInit(&argc, argv);    
    glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_DEPTH);
    glutInitWindowSize(screen_width,screen_height);
    glutInitWindowPosition(0,0);
    glutCreateWindow("Coursework 2");    
 
	glutDisplayFunc(DrawGLScene);
    glutMainLoop();

    return(0);    
}
thank you
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Perhaps I just missed it but where are you filling out the "texture[MAX_TEXTURES];" array with the textures generated in skybox.Init()? If this array isn't getting filled you are passing "junk" data into every call to glBindTexture. (Depends on your compiler as to what the default for int is)

Try filling out the array with tex1, tex2...etc from the Init function.

"Imagination is more important than knowledge" - A. Einstein
kk, see i missed that, cheers. I have changed my code to this
#include "stdafx.h"#include <GL/glut.h>#include <windows.h>#include <stdio.h>  //for file access							#include <gl\gl.h>													#include "skybox.h"#include "glbmp.h"bool skybox::LoadTexture(unsigned int & aTexture, const char * bitmap_file){   GLuint texture = 0; //OpenGL texture to create and return   glbmp_t bitmap;     //object to fill with data from glbmp       if(!glbmp_LoadBitmap(bitmap_file, 0, &bitmap))   {      fprintf(stderr, "Error loading bitmap file: %s\n", bitmap_file);   }    //generate and bind the OpenGL texture   glGenTextures(1, &texture);   glBindTexture(GL_TEXTURE_2D, texture);    //copy data from bitmap into texture   glTexImage2D(GL_TEXTURE_2D, 0, 3, bitmap.width, bitmap.height,                0, GL_RGB, GL_UNSIGNED_BYTE, bitmap.rgb_data);    //set up texture filtering   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);   glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);    //free the bitmap   glbmp_FreeBitmap(&bitmap);    return true;} void skybox::Init() {	OFFSET = 1/512.0; //set offset value for skybox	rot_x = 0.0; rot_y = 0.0;  	LoadTexture(texture[0], "images/left1.bmp");	LoadTexture(texture[1], "images/front1.bmp");	LoadTexture(texture[2], "images/right1.bmp");	LoadTexture(texture[3], "images/back1.bmp");	LoadTexture(texture[4], "images/down1.bmp");	LoadTexture(texture[5], "images/up1.bmp");}//This is where the magic happensvoid skybox::draw() {		glPushMatrix();	glRotated(rot_x, 1.0, 0.0, 0.0);	//Rotate around the x axis	glRotated(rot_y, 0.0, 1.0, 0.0);	//Rotate around the y axis	glColor3f(1.0f,1.0f,1.0f);			//Set colour to White	glEnable(GL_TEXTURE_2D);			//Enable texture mapping	glDisable (GL_DEPTH_TEST);			//Disable depth testing		//before you can use a texture you have to bind it		glBindTexture(GL_TEXTURE_2D, texture[0 + text_offset]);		glBegin (GL_QUADS);							glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET,0.0 + OFFSET);	glVertex3d (-10.0,-10.0,10.0);				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET,0.0 + OFFSET);	glVertex3d (-10.0,-10.0,-10.0);				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET,1.0 - OFFSET);	glVertex3d (-10.0,10.0,-10.0);				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET,1.0 - OFFSET);	glVertex3d (-10.0,10.0,10.0);		glEnd ();						glBindTexture(GL_TEXTURE_2D, texture[1 + text_offset]);		glBegin (GL_QUADS);						glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET,0.0 + OFFSET);	glVertex3d (-10.0,-10.0,-10.0);				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET,0.0 + OFFSET);	glVertex3d (10.0,-10.0,-10.0);				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET,1.0 - OFFSET);	glVertex3d (10.0,10.0,-10.0);				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET,1.0 - OFFSET);	glVertex3d (-10.0,10.0,-10.0);		glEnd ();		glBindTexture(GL_TEXTURE_2D, texture[2 + text_offset]);		glBegin (GL_QUADS);						glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,0.0 + OFFSET); glVertex3d (10.0,-10.0,-10.0);				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,0.0 + OFFSET); glVertex3d (10.0,-10.0,10.0);				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,1.0 - OFFSET); glVertex3d (10.0,10.0,10.0);				glNormal3d (0.0,0.0,10.0); glTexCoord2d (0.0 + OFFSET ,1.0 - OFFSET); glVertex3d (10.0,10.0,-10.0);		glEnd ();		glBindTexture(GL_TEXTURE_2D, texture[3 + text_offset]);			glBegin (GL_QUADS);						glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,0.0 + OFFSET); glVertex3d (10.0,-10.0,10.0);			glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,0.0 + OFFSET); glVertex3d (-10.0,-10.0,10.0);			glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,1.0 - OFFSET); glVertex3d (-10.0,10.0,10.0);			glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,1.0 - OFFSET); glVertex3d (10.0,10.0,10.0);				glEnd ();		glBindTexture(GL_TEXTURE_2D, texture[4 + text_offset]);			glBegin (GL_QUADS);						glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,0.0 + OFFSET); glVertex3d (-10.0,-10.0,10.0);			glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,0.0 + OFFSET); glVertex3d (10.0,-10.0,10.0);			glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,1.0 - OFFSET); glVertex3d (10.0,-10.0,-10.0);			glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,1.0 - OFFSET); glVertex3d (-10.0,-10.0,-10.0);				glEnd ();		glBindTexture(GL_TEXTURE_2D, texture[5 + text_offset]);		glBegin (GL_QUADS);						glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,0.0 + OFFSET); glVertex3d (-10.0,10.0,-10.0);				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,0.0 + OFFSET); glVertex3d (10.0,10.0,-10.0);				glNormal3d (0.0,0.0,1.0); glTexCoord2d (1.0 - OFFSET ,1.0 - OFFSET); glVertex3d (10.0,10.0,10.0);				glNormal3d (0.0,0.0,1.0); glTexCoord2d (0.0 + OFFSET ,1.0 - OFFSET); glVertex3d (-10.0,10.0,10.0);						glEnd ();	//Re-Enable the depth test	glEnable(GL_DEPTH_TEST);	//disable texture mapping	glDisable(GL_TEXTURE_2D);	glPopMatrix();	}


but for some odd reason, still black. Do you see what could be causing this?
now you are never setting your aTexture to the texture generated in LoadTexture...

Take it slower, look before you post :D.
"Imagination is more important than knowledge" - A. Einstein
I am trying to follow this
bool skybox::Load_Texture(unsigned int & aTexture, char * fileName) {	if(!fileName) return false;					//if no file name is given return	FILE *aFile = NULL;	AUX_RGBImageRec *image_record = NULL;	if((aFile = fopen(fileName, "rb")) == NULL) return false;	image_record = auxDIBImageLoadA(fileName);	//Function to load BMP	if(!image_record) return false;				//check that BMP loaded	glGenTextures(1, &aTexture);				//generates 1 texture name	glPixelStorei (GL_UNPACK_ALIGNMENT, 1);		//sets how the pixels of the texture are stored	glBindTexture(GL_TEXTURE_2D, aTexture);		//binds the name to the target													//build prefiltered textures at different resolutions	gluBuild2DMipmaps(GL_TEXTURE_2D, 3, image_record->sizeX, 					  image_record->sizeY, GL_RGB, GL_UNSIGNED_BYTE, image_record->data);												//give the texture its attributes	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR_MIPMAP_NEAREST);	glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);	// Now we need to free the image data that we loaded since openGL stored it as a texture	if (image_record) {							//if we stored data then free the memory		if (image_record->data) {				//check if there is any data			free(image_record->data);			//free the memory		}		free(image_record);						//free the image record	}	return true; //everything should have worked so return true}


But this is hard to follow as it is using the glaux library which i can no longer use. As a replacemet, i am using this code which is really long and complicated. Is there anything simular i can use which is simular to the above code?

This topic is closed to new replies.

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