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ragzzy-R
04-04-2013, 01:14 AM
Hi,
Im new to openGL.I've been following NEHE's tutorial and getting good grasp of OpenGL.previously I was using linux to practice NEHE lessons and i was happy with that.I was using SDL with OpenGL.recently i moved to windows 8.i know SDL is cross platform and with a little struggle i made SDL and OpenGL work with windows also.recently i was re-practicing all the lessons of NEHE from square 1 in windows and now the texture is not mapping to my cube.I stepped into the function that loads texture and for this line of code


if ( ( TextureImage[0] = SDL_LoadBMP( "nehe.bmp" ) ) )

I got this:


+ TextureImage[0] 0x00b74620 {flags=0 format=0x00b74678 w=256 ...} SDL_Surface *

i guess that means the texture is loaded correctly.but i see only a white cube.It was the same code that i used in linux which worked like a charm.I couldn't figure out what i did wrong.please help me with this.this is the function



int LoadGLTextures( )
{
/* Status indicator */
int Status = FALSE;

/* Create storage space for the texture */
SDL_Surface *TextureImage[1];

/* Load The Bitmap, Check For Errors, If Bitmap's Not Found Quit */
if ( ( TextureImage[0] = SDL_LoadBMP( "nehe.bmp" ) ) )
{

/* Set the status to true */
Status = TRUE;
;
/* Create The Texture */
glGenTextures( 1, &texture[0] );

/* Typical Texture Generation Using Data From The Bitmap */
glBindTexture( GL_TEXTURE_2D, texture[0] );

/* Generate The Texture */
glTexImage2D( GL_TEXTURE_2D, 0, 3, TextureImage[0]->w,
TextureImage[0]->h, 0, GL_RGB,
GL_UNSIGNED_BYTE, TextureImage[0]->pixels );


/* Linear Filtering */
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
}

/* Free up any memory we may have used */
if ( TextureImage[0] )
SDL_FreeSurface( TextureImage[0] );

return Status;
}


The image i use for texture is the default which nehe gives so it cant be an invalid image.also i guess SDL is loading the image perfectly but OpenGL is messing in mapping.though im not sure.please help me.thanks!!!

mobeen
04-04-2013, 02:57 AM
Hi,
I think the third parameter is the internal format which should be GL_RGB for your case. Replace this glTexImage2D call to this.


glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, TextureImage[0]->w, TextureImage[0]->h, 0, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[0]->pixels );


See if this helps,

ragzzy-R
04-04-2013, 03:31 AM
Hi,
I think the third parameter is the internal format which should be GL_RGB for your case. Replace this glTexImage2D call to this.


glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, TextureImage[0]->w, TextureImage[0]->h, 0, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[0]->pixels );


See if this helps,

still white cube bro! :(

mobeen
04-04-2013, 05:13 AM
still white cube bro! :(
Two things
1) Slight correction change the third param to GL_RGB8 instead of GL_RGB
2) Add this call after glGenTexture
glPixelStorei(GL_UNPACK_ALIGNMENT, 1)​

ragzzy-R
04-04-2013, 09:00 AM
Two things
1) Slight correction change the third param to GL_RGB8 instead of GL_RGB
2) Add this call after glGenTexture
glPixelStorei(GL_UNPACK_ALIGNMENT, 1)​

that didnt work. :( any other suggestions bro??

mobeen
04-04-2013, 09:09 AM
that didnt work. :( any other suggestions bro??
could u share your render function?
Another thing are u setting any initial opengl states for e.g. lighting etc.?

ragzzy-R
04-04-2013, 09:14 AM
could u share your render function?
Another thing are u setting any initial opengl states for e.g. lighting etc.?



here is the total code.As I said earlier its just the Lesson 6 from NEHE.




#include <stdio.h>
#include <stdlib.h>
#include <Windows.h>
#include <GL/gl.h>
#include <GL/glu.h>
#include "SDL.h"

/* screen width, height, and bit depth */
#define SCREEN_WIDTH 640
#define SCREEN_HEIGHT 480
#define SCREEN_BPP 16

/* Set up some booleans */
#define TRUE 1
#define FALSE 0

/* This is our SDL surface */
SDL_Surface *surface;

GLfloat xrot; /* X Rotation ( NEW ) */
GLfloat yrot; /* Y Rotation ( NEW ) */
GLfloat zrot; /* Z Rotation ( NEW ) */

GLuint texture[1]; /* Storage For One Texture ( NEW ) */

/* function to release/destroy our resources and restoring the old desktop */
void Quit( int returnCode )
{
/* clean up the window */
SDL_Quit( );

/* and exit appropriately */
exit( returnCode );
}

/* function to load in bitmap as a GL texture */
int LoadGLTextures( )
{
/* Status indicator */
int Status = FALSE;

/* Create storage space for the texture */
SDL_Surface *TextureImage[1];

/* Load The Bitmap, Check For Errors, If Bitmap's Not Found Quit */
if ( ( TextureImage[0] = SDL_LoadBMP( "nehe.bmp" ) ) )
{

/* Set the status to true */
Status = TRUE;
OutputDebugStringW(L"My output string.");
/* Create The Texture */
glGenTextures( 1, &texture[0] );
glPixelStorei(GL_UNPACK_ALIGNMENT,1);
/* Typical Texture Generation Using Data From The Bitmap */
glBindTexture( GL_TEXTURE_2D, texture[0] );

/* Generate The Texture
glTexImage2D( GL_TEXTURE_2D, 0, 3, TextureImage[0]->w,
TextureImage[0]->h, 0, GL_RGB,
GL_UNSIGNED_BYTE, TextureImage[0]->pixels );*/
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB8, TextureImage[0]->w, TextureImage[0]->h, 0, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[0]->pixels );
glGetError();

/* Linear Filtering */
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR );
glTexParameteri( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
}

/* Free up any memory we may have used */
if ( TextureImage[0] )
SDL_FreeSurface( TextureImage[0] );

return Status;
}

/* function to reset our viewport after a window resize */
int resizeWindow( int width, int height )
{
/* Height / width ration */
GLfloat ratio;

/* Protect against a divide by zero */
if ( height == 0 )
height = 1;

ratio = ( GLfloat )width / ( GLfloat )height;

/* Setup our viewport. */
glViewport( 0, 0, ( GLint )width, ( GLint )height );

/*
* change to the projection matrix and set
* our viewing volume.
*/
glMatrixMode( GL_PROJECTION );
glLoadIdentity( );

/* Set our perspective */
gluPerspective( 45.0f, ratio, 0.1f, 100.0f );

/* Make sure we're chaning the model view and not the projection */
glMatrixMode( GL_MODELVIEW );

/* Reset The View */
glLoadIdentity( );

return( TRUE );
}

/* function to handle key press events */
void handleKeyPress( SDL_keysym *keysym )
{
switch ( keysym->sym )
{
case SDLK_ESCAPE:
/* ESC key was pressed */
Quit( 0 );
break;
case SDLK_F1:
/* F1 key was pressed
* this toggles fullscreen mode
*/
SDL_WM_ToggleFullScreen( surface );
break;
default:
break;
}

return;
}

/* general OpenGL initialization function */
int initGL( GLvoid )
{

/* Load in the texture */
if ( !LoadGLTextures( ) )
return FALSE;

/* Enable Texture Mapping ( NEW ) */
glEnable( GL_TEXTURE_2D );
glGetError();
/* Enable smooth shading */
glShadeModel( GL_SMOOTH );

/* Set the background black */
glClearColor( 0.0f, 0.0f, 0.0f, 0.5f );

/* Depth buffer setup */
glClearDepth( 1.0f );

/* Enables Depth Testing */
glEnable( GL_DEPTH_TEST );

/* The Type Of Depth Test To Do */
glDepthFunc( GL_LEQUAL );

/* Really Nice Perspective Calculations */
glHint( GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST );

return( TRUE );
}

/* Here goes our drawing code */
int drawGLScene( GLvoid )
{
/* These are to calculate our fps */
static GLint T0 = 0;
static GLint Frames = 0;

/* Clear The Screen And The Depth Buffer */
glClear( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );

/* Move Into The Screen 5 Units */
glLoadIdentity( );
glTranslatef( 0.0f, 0.0f, -5.0f );

glRotatef( xrot, 1.0f, 0.0f, 0.0f); /* Rotate On The X Axis */
glRotatef( yrot, 0.0f, 1.0f, 0.0f); /* Rotate On The Y Axis */
glRotatef( zrot, 0.0f, 0.0f, 1.0f); /* Rotate On The Z Axis */

/* Select Our Texture */
glBindTexture( GL_TEXTURE_2D, texture[0] );

/* NOTE:
* The x coordinates of the glTexCoord2f function need to inverted
* for SDL because of the way SDL_LoadBmp loads the data. So where
* in the tutorial it has glTexCoord2f( 1.0f, 0.0f ); it should
* now read glTexCoord2f( 0.0f, 0.0f );
*/
glBegin(GL_QUADS);
/* Front Face */
/* Bottom Left Of The Texture and Quad */
glTexCoord2f( 0.0f, 1.0f ); glVertex3f( -1.0f, -1.0f, 1.0f );
/* Bottom Right Of The Texture and Quad */
glTexCoord2f( 1.0f, 1.0f ); glVertex3f( 1.0f, -1.0f, 1.0f );
/* Top Right Of The Texture and Quad */
glTexCoord2f( 1.0f, 0.0f ); glVertex3f( 1.0f, 1.0f, 1.0f );
/* Top Left Of The Texture and Quad */
glTexCoord2f( 0.0f, 0.0f ); glVertex3f( -1.0f, 1.0f, 1.0f );

/* Back Face */
/* Bottom Right Of The Texture and Quad */
glTexCoord2f( 0.0f, 0.0f ); glVertex3f( -1.0f, -1.0f, -1.0f );
/* Top Right Of The Texture and Quad */
glTexCoord2f( 0.0f, 1.0f ); glVertex3f( -1.0f, 1.0f, -1.0f );
/* Top Left Of The Texture and Quad */
glTexCoord2f( 1.0f, 1.0f ); glVertex3f( 1.0f, 1.0f, -1.0f );
/* Bottom Left Of The Texture and Quad */
glTexCoord2f( 1.0f, 0.0f ); glVertex3f( 1.0f, -1.0f, -1.0f );

/* Top Face */
/* Top Left Of The Texture and Quad */
glTexCoord2f( 1.0f, 1.0f ); glVertex3f( -1.0f, 1.0f, -1.0f );
/* Bottom Left Of The Texture and Quad */
glTexCoord2f( 1.0f, 0.0f ); glVertex3f( -1.0f, 1.0f, 1.0f );
/* Bottom Right Of The Texture and Quad */
glTexCoord2f( 0.0f, 0.0f ); glVertex3f( 1.0f, 1.0f, 1.0f );
/* Top Right Of The Texture and Quad */
glTexCoord2f( 0.0f, 1.0f ); glVertex3f( 1.0f, 1.0f, -1.0f );

/* Bottom Face */
/* Top Right Of The Texture and Quad */
glTexCoord2f( 0.0f, 1.0f ); glVertex3f( -1.0f, -1.0f, -1.0f );
/* Top Left Of The Texture and Quad */
glTexCoord2f( 1.0f, 1.0f ); glVertex3f( 1.0f, -1.0f, -1.0f );
/* Bottom Left Of The Texture and Quad */
glTexCoord2f( 1.0f, 0.0f ); glVertex3f( 1.0f, -1.0f, 1.0f );
/* Bottom Right Of The Texture and Quad */
glTexCoord2f( 0.0f, 0.0f ); glVertex3f( -1.0f, -1.0f, 1.0f );

/* Right face */
/* Bottom Right Of The Texture and Quad */
glTexCoord2f( 0.0f, 0.0f ); glVertex3f( 1.0f, -1.0f, -1.0f );
/* Top Right Of The Texture and Quad */
glTexCoord2f( 0.0f, 1.0f ); glVertex3f( 1.0f, 1.0f, -1.0f );
/* Top Left Of The Texture and Quad */
glTexCoord2f( 1.0f, 1.0f ); glVertex3f( 1.0f, 1.0f, 1.0f );
/* Bottom Left Of The Texture and Quad */
glTexCoord2f( 1.0f, 0.0f ); glVertex3f( 1.0f, -1.0f, 1.0f );

/* Left Face */
/* Bottom Left Of The Texture and Quad */
glTexCoord2f( 1.0f, 0.0f ); glVertex3f( -1.0f, -1.0f, -1.0f );
/* Bottom Right Of The Texture and Quad */
glTexCoord2f( 0.0f, 0.0f ); glVertex3f( -1.0f, -1.0f, 1.0f );
/* Top Right Of The Texture and Quad */
glTexCoord2f( 0.0f, 1.0f ); glVertex3f( -1.0f, 1.0f, 1.0f );
/* Top Left Of The Texture and Quad */
glTexCoord2f( 1.0f, 1.0f ); glVertex3f( -1.0f, 1.0f, -1.0f );
glEnd( );

/* Draw it to the screen */
SDL_GL_SwapBuffers( );

/* Gather our frames per second */
Frames++;
{
GLint t = SDL_GetTicks();
if (t - T0 >= 5000) {
GLfloat seconds = (t - T0) / 1000.0;
GLfloat fps = Frames / seconds;
//printf("%d frames in %g seconds = %g FPS\n", Frames, seconds, fps);
T0 = t;
Frames = 0;
}
}

xrot += 0.3f; /* X Axis Rotation */
yrot += 0.2f; /* Y Axis Rotation */
zrot += 0.4f; /* Z Axis Rotation */

return( TRUE );
}

int main( int argc, char **argv )
{
/* Flags to pass to SDL_SetVideoMode */
int videoFlags;
/* main loop variable */
int done = FALSE;
/* used to collect events */
SDL_Event event;
/* this holds some info about our display */
const SDL_VideoInfo *videoInfo;
/* whether or not the window is active */
int isActive = TRUE;

/* initialize SDL */
if ( SDL_Init( SDL_INIT_VIDEO ) < 0 )
{
fprintf( stderr, "Video initialization failed: %s\n",
SDL_GetError( ) );
Quit( 1 );
}

/* Fetch the video info */
videoInfo = SDL_GetVideoInfo( );

if ( !videoInfo )
{
fprintf( stderr, "Video query failed: %s\n",
SDL_GetError( ) );
Quit( 1 );
}

/* the flags to pass to SDL_SetVideoMode */
videoFlags = SDL_OPENGL; /* Enable OpenGL in SDL */
videoFlags |= SDL_GL_DOUBLEBUFFER; /* Enable double buffering */
videoFlags |= SDL_HWPALETTE; /* Store the palette in hardware */
videoFlags |= SDL_RESIZABLE; /* Enable window resizing */

/* This checks to see if surfaces can be stored in memory */
if ( videoInfo->hw_available )
videoFlags |= SDL_HWSURFACE;
else
videoFlags |= SDL_SWSURFACE;

/* This checks if hardware blits can be done */
if ( videoInfo->blit_hw )
videoFlags |= SDL_HWACCEL;

/* Sets up OpenGL double buffering */
SDL_GL_SetAttribute( SDL_GL_DOUBLEBUFFER, 1 );

/* get a SDL surface */
surface = SDL_SetVideoMode( SCREEN_WIDTH, SCREEN_HEIGHT, SCREEN_BPP,
videoFlags );

/* Verify there is a surface */
if ( !surface )
{
fprintf( stderr, "Video mode set failed: %s\n", SDL_GetError( ) );
Quit( 1 );
}

/* initialize OpenGL */
initGL( );

/* resize the initial window */
resizeWindow( SCREEN_WIDTH, SCREEN_HEIGHT );

/* wait for events */
while ( !done )
{
/* handle the events in the queue */

while ( SDL_PollEvent( &event ) )
{
switch( event.type )
{
case SDL_ACTIVEEVENT:
/* Something's happend with our focus
* If we lost focus or we are iconified, we
* shouldn't draw the screen
*/
if ( event.active.gain == 0 )
isActive = FALSE;
else
isActive = TRUE;
break;
case SDL_VIDEORESIZE:
/* handle resize event */
surface = SDL_SetVideoMode( event.resize.w,
event.resize.h,
16, videoFlags );
if ( !surface )
{
fprintf( stderr, "Could not get a surface after resize: %s\n", SDL_GetError( ) );
Quit( 1 );
}
resizeWindow( event.resize.w, event.resize.h );
break;
case SDL_KEYDOWN:
/* handle key presses */
handleKeyPress( &event.key.keysym );
break;
case SDL_QUIT:
/* handle quit requests */
done = TRUE;
break;
default:
break;
}
}

/* draw the scene */
if ( isActive )
drawGLScene( );
}

/* clean ourselves up and exit */
Quit( 0 );

/* Should never get here */
return( 0 );
}

mobeen
04-04-2013, 06:39 PM
Hi,
I had a look through your code in detail and I know why it is not working.
When the resize event is raised the GLcontext is deleted and a new context is made. This unfortunately removes all of the previous OpenGL states as well as textures.
The solution is to either remove SDL_VIDEORESIZE event altogether (if you are calling resize and initGL before the msg loop) or calling your initGL function after the resizeWindow function (you will then have to remove the redundant call to resizeWindow initGL before the msg loop.


case SDL_VIDEORESIZE:
//handle resize event
surface = SDL_SetVideoMode( event.resize.w,
event.resize.h,
SCREEN_BPP, videoFlags );
if ( !surface )
{
fprintf( stderr, "Could not get a surface after resize: %s\n", SDL_GetError( ) );
Quit( 1 );
}
resizeWindow( event.resize.w, event.resize.h );
initGL();
break;

ragzzy-R
04-05-2013, 03:49 AM
aaaaaaaaaaaaahhhhhhhhhhhhhhh thank u brother I LOVE U!!!! seriously Ive been scratching my head for days on this!!thank u for helping.its good to have people like u!! BTW i was wondering one thing! if it was abt the GLcontext how could this code work on linux and trouble on windows??

mobeen
04-05-2013, 04:41 AM
That is something SDL should give you a better answer. It seems to me that whenever you call SDL_SetVideoMode a new GL context is created. Beats me why this was working on LINUX.

ragzzy-R
04-06-2013, 09:28 AM
ohh thanks!! :)