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MylesEvans

OpenGL
Texture wont show on quad.

7 posts in this topic

I made this thread in For Beginners, but noone there was able to help.

 

 

I was having trouble loading the image, but have since fixed that. Now I cant seem to get the image to actually show on the screen. Instead its just the blue rectangle I have drawn with no texture on it.

 

#include "SDL.h"
#include "SDL_image.h"
#include "SDL_opengl.h"
#include <math.h>
#include <stdio.h>

int loadImage();
void drawImage();

extern SDL_Event event;

GLuint texture = NULL;
GLenum texture_format=NULL;
GLint nofcolors;

bool initGL()
{
    //Initialize Projection Matrix
    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();

    //Initialize Modelview Matrix
    glOrtho(0, 1200, 700, 0, -1, 1);
	glMatrixMode( GL_MODELVIEW );
    glLoadIdentity();

    //Initialize clear color
   glClearColor(1.0,.4,0.0,0.0);
   glEnable( GL_TEXTURE_2D);
    //Check for error
    GLenum error = glGetError();
    if( error != GL_NO_ERROR )
    {
        printf( "Error initializing OpenGL! %s\n", gluErrorString( error ) );
        return false;
    }

    return true;
}

bool init()
{
    //Initialize SDL
    if( SDL_Init( SDL_INIT_EVERYTHING ) < 0 )
    {
        return false;
    }

	SDL_GL_SetAttribute(SDL_GL_DOUBLEBUFFER,1);

    //Create Window
    if( SDL_SetVideoMode( SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP, SDL_OPENGL ) == NULL )
    {
        return false;
    }

    //Enable unicode
    SDL_EnableUNICODE( SDL_TRUE );

	


    //Initialize OpenGL
    if( initGL() == false )
    {
        return false;
    }

    //Set caption
    SDL_WM_SetCaption( "Project Birth Game Window. Guns&Player.", NULL );

    return true;
}




int main( int argc, char *argv[] )
{
    //Quit flag
    bool quit = false;

    //Initialize
    if( init() == false )
    {
        return 1;
    }

    //The frame rate regulator
    Timer fps;
	fps.start();
	loadImage(); 


	int x = 0, y = 0;
	//Wait for user exit
	while( quit == false )
	{
        //Start the frame timer
        
		
        //While there are events to handle
		while( SDL_PollEvent( &event ) )
		{
			if( event.type == SDL_QUIT )
			{
                quit = true;
            }
			
			else if( event.type == SDL_KEYDOWN )
            {
                //Handle keypress with current mouse position
                
				SDL_GetMouseState( &x, &y );
                
			}
		}

	
		drawImage(); 

       
        update(); 
		
		SDL_GL_SwapBuffers();
		
        //Cap the frame rate
        if( fps.get_ticks() < 1000 / FRAMES_PER_SECOND )
        {
            SDL_Delay( ( 1000 / FRAMES_PER_SECOND ) - fps.get_ticks() );
        }
	}

	//Clean up
	clean_up();

	return 0;
}




int loadImage()
{


	SDL_Surface* surface;
	
	
	if((surface = IMG_Load("Avatar Basic Character Model.jpg")))
	{
	
		

	//get number of channels in the SDL surface
	nofcolors = surface -> format -> BytesPerPixel;
	
   //contains an alpha channel
	if(nofcolors == 4)
	{
		if ( surface -> format -> Rmask == 0x000000ff)
			texture_format = GL_RGBA;
		else
			texture_format = GL_BGRA;
	}
	else if ( nofcolors == 3) //no alpha channel
	{
		if(surface ->format->Rmask==0x000000ff)
			texture_format=GL_RGB;
		else
			texture_format=GL_BGR;
	}

	//Have Opengl generate a texture object handle for us
	glGenTextures(1, &texture);

	//Bind the texture object
	glBindTexture( GL_TEXTURE_2D, texture);

	//Set the texture's stretching properties
	glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glPixelStorei(GL_UNPACK_ALIGNMENT,1);

	
	glTexImage2D( GL_TEXTURE_2D, 0, nofcolors, surface -> w, surface ->h, 0, texture_format, GL_UNSIGNED_BYTE, surface -> pixels );
	
	}
	else //could not load image
		return -1;


if (surface)
{
	SDL_FreeSurface(surface);
}

return 1; 

}


void drawImage()
{

	//Clear the screen before drawing 
	glClear( GL_COLOR_BUFFER_BIT);

	//Bind the texture to which subsequent calls refer to
	glBindTexture( GL_TEXTURE_2D, texture);

	glPushMatrix();
	glTranslatef(300,300,0.0f);
	glBegin(GL_QUADS);
	//Set color
	glColor4f(0.0,0.0,1.0,0.0);

	
	glTexCoord2i(1,1);
	glVertex2f(150.0,0);//bottom right
	
	glTexCoord2i(0,1);
	glVertex2f(150.0,-50);//top right
	
	glTexCoord2i(0,0);
	glVertex2f(0.0,-50);//top left
	
	glTexCoord2i(1,0);
	glVertex2f(0.0,0);//bottom left
    

	glEnd();
	
	glPopMatrix();

	
}

 

At first I was having issues with loading the image, but thats no longer an issue. Any idea on why the image wont show on the quad? Perhaps an issue with binding?

 

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The code works as it is for me. Check for OpenGL errors in your code.

The image shows on screen for you? How can that be?

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Probably because there's nothing wrong with the code itself, but the environment in which you run it. For example, you may be trying to load a non-power of two texture in an environment that can only handle power of two textures. As I said, check for errors.

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Also this is not related to your question but you may find it helpful anyway to know that when using C++ you should use the C++ headers instead of the C headers.

 

#include <math.h> #include <cmath>

#include <stdio.h> #include <cstdio>

 

 

L. Spiro

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Also this is not related to your question but you may find it helpful anyway to know that when using C++ you should use the C++ headers instead of the C headers.
 
#include <math.h> #include <cmath>
#include <stdio.h> #include <cstdio>
 
 
L. Spiro

while fair enough, it is not made clear here that the code in question is C++, rather than C99 (clarification: C code looking like that given will generally be accepted by GCC, which implements C99 support, well, along with much of C11). (this comment is N/A if in-fact the OP is using C++). Edited by cr88192
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Something else to mention to the original topic-poster: Fixed your random-style indentations. You have random indentations all over the place. Why? It is just shooting yourself in the foot.
There are guidelines for indenting that, time-tested and mother-approved, will help both you and anyone else read your code. You should adhere to indentation guidelines strictly.


L. Spiro
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