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[FIXED] Isometric View + Texturing? (OpenGL)


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#1 Jungletoe   Members   -  Reputation: 225

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Posted 27 November 2011 - 06:18 PM

FIXED, THANKS!
(SOURCE INCLUDED @ LAST POST)



INTRODUCTION


I've begun work on a 3D OpenGL isometric game engine. Lately I've attempted two things:
1) Texturing a Cube with a .BMP
2) Setting up an Isometric View


PROBLEM

I found the code for the isometric view on GameDev.net and the code for the texturing here. When using the two snippets separately, they work. When using them together, they don't and look like like this:
Posted Image



As you can see, it is textured properly, yet it's not isometric. I think this is due to the isometric code messing up the view.

Here is the isometric code that I put in my init() function:

void init()
{
	glClearColor(0.0, 0.0, 0.0, 1.0); //RGB + Alpha
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(45, 640 / 480, 1.0, 500.0); //sets camera params
	glMatrixMode(GL_MODELVIEW);
	SDL_WM_SetCaption( "OpenGL Game", NULL );
	glShadeModel(GL_SMOOTH);
	glEnable(GL_DEPTH_TEST);

	// ISOMETRIC VIEW CODE
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(-100.0f, 100.0f, -100.0f, 100.0f, -500.0f, 500.0f);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	glRotatef(35.264f, 1.0f, 0.0f, 0.0f);
	glRotatef(-45.0f, 0.0f, 1.0f, 0.0f);
	glScalef(1.0f, 1.0f, -1.0f);

	Image* image = loadBMP("vtr.bmp");
	_textureId = loadTexture(image);
	delete image;
}


When I take out the isometric code part it works perfectly, but isn't isometric (this is just some extra coloring stuff I did too, it won't affect the texturing):

Posted Image



CONCLUSION


I need to figure out how to make my objects show up isometrically while also allowing me to use textures. Do any of you know any isometric code that would work to set up an isometric camera? I've tried a couple of codes from different people without success.

Sponsor:

#2 Kyall   Members   -  Reputation: 287

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Posted 27 November 2011 - 07:52 PM

You shouldn't be transforming your geometry like that to achieve an isometric effect. To achieve an isometric effect you only need to set your camera in the correct position and use an isometric projection.


// Set projection transform
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
void glOrtho(GLdouble left, GLdouble right, GLdouble bottom, GLdouble top, GLdouble nearVal, GLdouble farVal);

// Set view transform
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
gluLookAt(GLdouble eyeX, GLdouble eyeY, GLdouble eyeZ, GLdouble centerX, GLdouble centerY, GLdouble centerZ, GLdouble upX, GLdouble upY, GLdouble upZ);


// When drawing an object or a set of objects
glMatrixMode(GL_MODELVIEW);
glPushMatrix();


-- Use transforms here to set an object or set of objects in the correct position in world space
-- Draw geometry for such here


glPopMatrix();




I say Code! You say Build! Code! Build! Code! Build! Can I get a woop-woop? Woop! Woop!

#3 Jungletoe   Members   -  Reputation: 225

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Posted 28 November 2011 - 10:53 PM

What are the values inside glLookAt(); ?

When I use your code with the supposed inputs:

	// Set projection transform 
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity(); 
	glOrtho(-1.0,1.0,-1.0,1.0,-1.0,1.0);

	// Set view transform 
	glMatrixMode(GL_MODELVIEW); 
	glLoadIdentity(); 
	gluLookAt(1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0., 1.0, 0.0);


It gives me this:

Posted Image



EDIT:
Hell, I'll just post all my source code...

TEXTURED ATTEMPT: (gives me a blank screen)

//*******************************************************************************************************************//
//********************************************* 	HEADERS    ******************************************************//
//*******************************************************************************************************************//

// specific headers
#include "SDL.h"
#include "SDL_opengl.h"
#include "GL/glut.h"
#include "imageloader.h"
#include <iostream>
#include <stdio.h>


const int triangle = 1;
float angle = 0.0;
GLuint _textureId; //The id of the texture

//Makes the image into a texture, and returns the id of the texture
GLuint loadTexture(Image* image) {
	GLuint textureId;
	glGenTextures(1, &textureId); //Make room for our texture
	glBindTexture(GL_TEXTURE_2D, textureId); //Tell OpenGL which texture to edit
	//Map the image to the texture
	glTexImage2D(GL_TEXTURE_2D,                //Always GL_TEXTURE_2D
			     0,                            //0 for now
			     GL_RGB,                   	//Format OpenGL uses for image
			     image->width, image->height,  //Width and height
			     0,                            //The border of the image
			     GL_RGB, //GL_RGB, because pixels are stored in RGB format
			     GL_UNSIGNED_BYTE, //GL_UNSIGNED_BYTE, because pixels are stored
			                       //as unsigned numbers
			     image->pixels);           	//The actual pixel data
	return textureId; //Returns the id of the texture
}




void drawCube(float size)
{
	glEnable(GL_TEXTURE_2D);
	glBindTexture(GL_TEXTURE_2D, _textureId);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	glColor3f(1.0f, 1.0f, 1.0f);
	
	glBegin(GL_QUADS);
		//front face
		glColor3f(1.0, 1.0, 1.0);
		glVertex3f(size/2, size/2, size/2);		//glTexCoord2f(0.0f, 0.0f);
		glVertex3f(-size/2, size/2, size/2);	//glTexCoord2f(1.0f, 0.0f);
		glVertex3f(-size/2, -size/2, size/2);	//glTexCoord2f(1.0f, 1.0f);
		glVertex3f(size/2, -size/2, size/2);	//glTexCoord2f(0.0f, 1.0f);

		//left face
		glColor3f(0.0, 1.0, 0.0);
		glVertex3f(-size/2, size/2, size/2);
		glVertex3f(-size/2, size/2, -size/2);
		glVertex3f(-size/2, -size/2, -size/2);
		glVertex3f(-size/2, -size/2, size/2);

		//back face
		glColor3f(1.0, 0.0, 1.0);
		glVertex3f(size/2, size/2, -size/2);
		glVertex3f(-size/2, size/2, -size/2);
		glVertex3f(-size/2, -size/2, -size/2);
		glVertex3f(size/2, -size/2, -size/2);

		//right face
		glColor3f(0.5, 0.5, 0.5);
		glVertex3f(size/2, size/2, -size/2);
		glVertex3f(size/2, size/2, size/2);
		glVertex3f(size/2, -size/2, size/2);
		glVertex3f(size/2, -size/2, -size/2);

		//top face	
		glColor3f(1.0, 0.5, 1.0);
		glVertex3f(size/2, size/2, size/2);
		glVertex3f(-size/2, size/2, size/2);
		glVertex3f(-size/2, size/2, -size/2);
		glVertex3f(size/2, size/2, -size/2);

		//bottom face
		glColor3f(1.0, 1.0, 1.0);
		glVertex3f(size/2, -size/2, size/2);
		glVertex3f(-size/2, -size/2, size/2);
		glVertex3f(-size/2, -size/2, -size/2);
		glVertex3f(size/2, -size/2, -size/2);
	glEnd();
}

void init()
{
	// Set projection transform 
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity(); 
	glOrtho(-1.0,1.0,-1.0,1.0,-1.0,1.0);

	// Set view transform 
	glMatrixMode(GL_MODELVIEW); 
	glLoadIdentity(); 
	gluLookAt(1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0., 1.0, 0.0);

	Image* image = loadBMP("vtr.bmp");
	_textureId = loadTexture(image);
	delete image;
}

void display(){
	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
	glLoadIdentity();

	//glTranslatef(0.0, 0.0, -5.0);
	//glRotatef(angle, 1.0, 1.0, 1.0);
	drawCube(10.0);
}


int main( int agrc, char* args[] )
{
	SDL_Init(SDL_INIT_EVERYTHING);
	SDL_Surface* screen=SDL_SetVideoMode(600,400,32, SDL_SWSURFACE|SDL_OPENGL );
	bool running = true;
	Uint32 start;
	SDL_Event event;
	init();

	while(running)
	{
		start=SDL_GetTicks();
		while(SDL_PollEvent(&event))
		{
			switch(event.type)
			{
				case SDL_QUIT:
					running = false;
					break;
			}
		}
		display();
		SDL_GL_SwapBuffers();
		angle+=0.1;
		if(angle > 360)
			angle -= 360;
		if(1000/30>(SDL_GetTicks()-start))
			SDL_Delay(1000/30>(SDL_GetTicks()-start));
	}

	SDL_FreeSurface(screen);
	SDL_Quit();
	return 0;
}



NON-TEXTURED ATTEMPT: (gives me picture above)

/* ************************************************************************************************ */
/* ******************************            INCLUDES       	*********************************** */
/* ************************************************************************************************ */


#include "SDL.h"
#include "SDL_opengl.h"
#include "stdio.h"
#include <string>
#include "CubeTypes.h"

const int triangle = 1;
float currentX = 0.0;
float currentY = 0.0;
float currentZ = 0.0;

/* ************************************************************************************************ */
/* *********************                      INIT              *********************************** */
/* ************************************************************************************************ */
void init()
{
	/*
	glClearColor(0.0, 0.0, 0.0, 1.0); //RGB + Alpha
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	gluPerspective(45, 640 / 480, 1.0, 500.0); //sets camera params
	glMatrixMode(GL_MODELVIEW);
	SDL_WM_SetCaption( "OpenGL Game", NULL );
	glShadeModel(GL_SMOOTH);
	glEnable(GL_DEPTH_TEST);
	glEnable(GL_TEXTURE_2D);
	glEnable(GL_ALPHA_TEST);
	glAlphaFunc(GL_GREATER, 0.5);
	*/

	// Set projection transform 
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity(); 
	glOrtho(-1.0,1.0,-1.0,1.0,-1.0,1.0);

	// Set view transform 
	glMatrixMode(GL_MODELVIEW); 
	glLoadIdentity(); 
	gluLookAt(1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0., 1.0, 0.0);
}

/* ************************************************************************************************ */
/* *********************                 	DISPLAY            *********************************** */
/* ************************************************************************************************ */

void display(){
	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
	glLoadIdentity();

	//glTranslatef(0.0, 0.0, -5.0);
	//glRotatef( 0.0 , 1.0, 1.0, 1.0);

	glMatrixMode(GL_PROJECTION);
	glLoadIdentity();
	glOrtho(-100.0f, 100.0f, -100.0f, 100.0f, -500.0f, 500.0f);
	glMatrixMode(GL_MODELVIEW);
	glLoadIdentity();
	glRotatef(35.264f, 1.0f, 0.0f, 0.0f);
	glRotatef(-45.0f, 0.0f, 1.0f, 0.0f);
	glScalef(1.0f, 1.0f, -1.0f);

	//current cube position
	//drawSand(currentX, currentY, currentZ);

	//drawDirt(1.0, 0.0, 0.0);
	drawSand(0.0, 0.0, 0.0);
	//drawSand(1.0, 0.0, 1.0);
	//drawSand(1.0, 1.0, 1.0);
	//drawDirt(2.0, 0.0, 1.0);
	//drawDirt(2.0, 0.0, 0.0);

}

/* ************************************************************************************************ */
/* *********************                    MAIN                *********************************** */
/* ************************************************************************************************ */

int main( int agrc, char* args[] )
{
	SDL_Init(SDL_INIT_EVERYTHING);
	SDL_Surface* screen=SDL_SetVideoMode(600,400,32, SDL_SWSURFACE|SDL_OPENGL );
	bool running = true;
	Uint32 start;
	SDL_Event event;
	init();

	while(running)
	{
		start=SDL_GetTicks();
		if (SDL_PollEvent(&event))
		{
			if (event.type == SDL_QUIT){
				running = false;
			}

			if (event.type == SDL_KEYDOWN){
				SDLKey keyPressed = event.key.keysym.sym;
   
				switch (keyPressed)
				{
					case SDLK_ESCAPE:
						running = false;
						break;
				}
			}
		}
		display();
		SDL_GL_SwapBuffers();
		if(1000/30>(SDL_GetTicks()-start))
			SDL_Delay(1000/30>(SDL_GetTicks()-start));
	}

	SDL_Quit();
	return 0;
}


#4 Kyall   Members   -  Reputation: 287

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Posted 28 November 2011 - 11:33 PM

From the looks of things, you're using glLookAt properly, the first 3 values are the world space position of the camera eye, the next three values are the world space position of where the eye is looking, and the last 3 values are an up vector to determine the roll of the camera.
You need to give openGL texture coordinates for each of the vertices as well as position.

http://www.opengl.or.../glTexCoord.xml

I noticed that you had glTexCoord2f commented out. Your texture binding looks fine, also:


glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri
(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri
(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri
(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);

You can move that code to the loadTexture function if you want, you don't have to set it before drawing if it's already set for the texture you're binding.
I say Code! You say Build! Code! Build! Code! Build! Can I get a woop-woop? Woop! Woop!

#5 Jungletoe   Members   -  Reputation: 225

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Posted 30 November 2011 - 11:11 PM

I changed the code and got the same result as the "Textured-Attempt" picture above. Here's the code again:




//*******************************************************************************************************************//
//*********************************************     HEADERS    ******************************************************//
//*******************************************************************************************************************//

// specific headers
#include "SDL.h"
#include "SDL_opengl.h"
#include "GL/glut.h"
#include "imageloader.h"
#include <iostream>
#include <stdio.h>


const int triangle = 1;
float angle = 0.0;
GLuint _textureId; //The id of the texture

//Makes the image into a texture, and returns the id of the texture
GLuint loadTexture(Image* image) {
	GLuint textureId;
	glGenTextures(1, &textureId); //Make room for our texture
	glBindTexture(GL_TEXTURE_2D, textureId); //Tell OpenGL which texture to edit
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	//Map the image to the texture
	glTexImage2D(GL_TEXTURE_2D,                //Always GL_TEXTURE_2D
				 0,                            //0 for now
				 GL_RGB,                       //Format OpenGL uses for image
				 image->width, image->height,  //Width and height
				 0,                            //The border of the image
				 GL_RGB, //GL_RGB, because pixels are stored in RGB format
				 GL_UNSIGNED_BYTE, //GL_UNSIGNED_BYTE, because pixels are stored
				                   //as unsigned numbers
				 image->pixels);               //The actual pixel data
	return textureId; //Returns the id of the texture
}




void drawCube(float size)
{
	glEnable(GL_TEXTURE_2D);
	glBindTexture(GL_TEXTURE_2D, _textureId);
	glColor3f(1.0f, 1.0f, 1.0f);
	
	glBegin(GL_QUADS);
		// Front Face
		glTexCoord2f(0.0f, 0.0f); glVertex3f(-.5f, -.5f,  .5f);  // Bottom Left Of The Texture and Quad
		glTexCoord2f(1.0f, 0.0f); glVertex3f( .5f, -.5f,  .5f);  // Bottom Right Of The Texture and Quad
		glTexCoord2f(1.0f, 1.0f); glVertex3f( .5f,  .5f,  .5f);  // Top Right Of The Texture and Quad
		glTexCoord2f(0.0f, 1.0f); glVertex3f(-.5f,  .5f,  .5f);  // Top Left Of The Texture and Quad

		// Back Face
		glTexCoord2f(1.0f, 0.0f); glVertex3f(-.5f, -.5f, -.5f);  // Bottom Right Of The Texture and Quad
		glTexCoord2f(1.0f, 1.0f); glVertex3f(-.5f,  .5f, -.5f);  // Top Right Of The Texture and Quad
		glTexCoord2f(0.0f, 1.0f); glVertex3f( .5f,  .5f, -.5f);  // Top Left Of The Texture and Quad
		glTexCoord2f(0.0f, 0.0f); glVertex3f( .5f, -.5f, -.5f);  // Bottom Left Of The Texture and Quad

		// Top Face
		glTexCoord2f(0.0f, 1.0f); glVertex3f(-.5f,  .5f, -.5f);  // Top Left Of The Texture and Quad
		glTexCoord2f(0.0f, 0.0f); glVertex3f(-.5f,  .5f,  .5f);  // Bottom Left Of The Texture and Quad
		glTexCoord2f(1.0f, 0.0f); glVertex3f( .5f,  .5f,  .5f);  // Bottom Right Of The Texture and Quad
		glTexCoord2f(1.0f, 1.0f); glVertex3f( .5f,  .5f, -.5f);  // Top Right Of The Texture and Quad

		// Bottom Face
		glTexCoord2f(1.0f, 1.0f); glVertex3f(-.5f, -.5f, -.5f);  // Top Right Of The Texture and Quad
		glTexCoord2f(0.0f, 1.0f); glVertex3f( .5f, -.5f, -.5f);  // Top Left Of The Texture and Quad
		glTexCoord2f(0.0f, 0.0f); glVertex3f( .5f, -.5f,  .5f);  // Bottom Left Of The Texture and Quad
		glTexCoord2f(1.0f, 0.0f); glVertex3f(-.5f, -.5f,  .5f);  // Bottom Right Of The Texture and Quad

		// Right face
		glTexCoord2f(1.0f, 0.0f); glVertex3f( .5f, -.5f, -.5f);  // Bottom Right Of The Texture and Quad
		glTexCoord2f(1.0f, 1.0f); glVertex3f( .5f,  .5f, -.5f);  // Top Right Of The Texture and Quad
		glTexCoord2f(0.0f, 1.0f); glVertex3f( .5f,  .5f,  .5f);  // Top Left Of The Texture and Quad
		glTexCoord2f(0.0f, 0.0f); glVertex3f( .5f, -.5f,  .5f);  // Bottom Left Of The Texture and Quad

		// Left Face
		glTexCoord2f(0.0f, 0.0f); glVertex3f(-.5f, -.5f, -.5f);  // Bottom Left Of The Texture and Quad
		glTexCoord2f(1.0f, 0.0f); glVertex3f(-.5f, -.5f,  .5f);  // Bottom Right Of The Texture and Quad
		glTexCoord2f(1.0f, 1.0f); glVertex3f(-.5f,  .5f,  .5f);  // Top Right Of The Texture and Quad
		glTexCoord2f(0.0f, 1.0f); glVertex3f(-.5f,  .5f, -.5f);  // Top Left Of The Texture and Quad
	glEnd();
}

void init()
{
	// Set projection transform 
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity(); 
	glOrtho(-1.0,1.0,-1.0,1.0,-1.0,1.0);

	// Set view transform 
	glMatrixMode(GL_MODELVIEW); 
	glLoadIdentity(); 
	gluLookAt(1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0., 1.0, 0.0);

	Image* image = loadBMP("vtr.bmp");
	_textureId = loadTexture(image);
	delete image;
}

void display(){
	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);
	glLoadIdentity();

	//glTranslatef(0.0, 0.0, -5.0);
	//glRotatef(angle, 1.0, 1.0, 1.0);
	drawCube(10.0);
}


int main( int agrc, char* args[] )
{
	SDL_Init(SDL_INIT_EVERYTHING);
	SDL_Surface* screen=SDL_SetVideoMode(600,400,32, SDL_SWSURFACE|SDL_OPENGL );
	bool running = true;
	Uint32 start;
	SDL_Event event;
	init();

	while(running)
	{
		start=SDL_GetTicks();
		while(SDL_PollEvent(&event))
		{
			switch(event.type)
			{
				case SDL_QUIT:
					running = false;
					break;
			}
		}
		display();
		SDL_GL_SwapBuffers();
		angle+=0.1;
		if(angle > 360)
			angle -= 360;
		if(1000/30>(SDL_GetTicks()-start))
			SDL_Delay(1000/30>(SDL_GetTicks()-start));
	}

	SDL_FreeSurface(screen);
	SDL_Quit();
	return 0;
}


And here is the pic of what it does:
Posted Image

I've literally followed every single tutorial for isometric views on the internet and all give the exact same code you gave, so I'm very curious as to why this wont work. I've also tried commenting out various chunks/line of the code to see if it would work but to no success.

Any more ideas? You've been great so far!

#6 Syranide   Members   -  Reputation: 375

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Posted 01 December 2011 - 04:16 AM

Aren't you setting the modelview matrix to identity every time you render a new frame? It sure seems so to me.



#7 Jungletoe   Members   -  Reputation: 225

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Posted 01 December 2011 - 08:04 PM

Aren't you setting the modelview matrix to identity every time you render a new frame? It sure seems so to me.


THANK YOU SO MUCH!

I commented out glLoadIdentity and it now gives me this:
Posted Image


I'm still kind of curious as to why it only prints that pyramid-looking shape though... My code hasn't changed from my above post besides commenting out glLoadIdentity.

#8 Jungletoe   Members   -  Reputation: 225

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Posted 01 December 2011 - 08:51 PM


FIXED


For the sake of helping the community, here is all my source code along with the product. Thanks so much!



//*******************************************************************************************************************//
//********************************************* 	HEADERS    ******************************************************//
//*******************************************************************************************************************//

// specific headers
#include "SDL.h"
#include "SDL_opengl.h"
#include "GL/glut.h"
#include "imageloader.h"
#include <iostream>
#include <stdio.h>


const int triangle = 1;
float angle = 0.0;
GLuint _textureId; //The id of the texture

//Makes the image into a texture, and returns the id of the texture
GLuint loadTexture(Image* image) {
	GLuint textureId;
	glGenTextures(1, &textureId); //Make room for our texture
	glBindTexture(GL_TEXTURE_2D, textureId); //Tell OpenGL which texture to edit
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
	//Map the image to the texture
	glTexImage2D(GL_TEXTURE_2D,                //Always GL_TEXTURE_2D
			     0,                            //0 for now
			     GL_RGB,                   	//Format OpenGL uses for image
			     image->width, image->height,  //Width and height
			     0,                            //The border of the image
			     GL_RGB, //GL_RGB, because pixels are stored in RGB format
			     GL_UNSIGNED_BYTE, //GL_UNSIGNED_BYTE, because pixels are stored
			                       //as unsigned numbers
			     image->pixels);           	//The actual pixel data
	return textureId; //Returns the id of the texture
}




void drawCube(float size)
{
	glEnable(GL_TEXTURE_2D);
	glBindTexture(GL_TEXTURE_2D, _textureId);
	glColor3f(1.0f, 1.0f, 1.0f);
	
	glBegin(GL_QUADS);
		// Front Face
		glTexCoord2f(0.0f, 0.0f); glVertex3f(-.5f, -.5f,  .5f);  // Bottom Left Of The Texture and Quad
		glTexCoord2f(1.0f, 0.0f); glVertex3f( .5f, -.5f,  .5f);  // Bottom Right Of The Texture and Quad
		glTexCoord2f(1.0f, 1.0f); glVertex3f( .5f,  .5f,  .5f);  // Top Right Of The Texture and Quad
		glTexCoord2f(0.0f, 1.0f); glVertex3f(-.5f,  .5f,  .5f);  // Top Left Of The Texture and Quad

		// Back Face
		glTexCoord2f(1.0f, 0.0f); glVertex3f(-.5f, -.5f, -.5f);  // Bottom Right Of The Texture and Quad
		glTexCoord2f(1.0f, 1.0f); glVertex3f(-.5f,  .5f, -.5f);  // Top Right Of The Texture and Quad
		glTexCoord2f(0.0f, 1.0f); glVertex3f( .5f,  .5f, -.5f);  // Top Left Of The Texture and Quad
		glTexCoord2f(0.0f, 0.0f); glVertex3f( .5f, -.5f, -.5f);  // Bottom Left Of The Texture and Quad

		// Top Face
		glTexCoord2f(0.0f, 1.0f); glVertex3f(-.5f,  .5f, -.5f);  // Top Left Of The Texture and Quad
		glTexCoord2f(0.0f, 0.0f); glVertex3f(-.5f,  .5f,  .5f);  // Bottom Left Of The Texture and Quad
		glTexCoord2f(1.0f, 0.0f); glVertex3f( .5f,  .5f,  .5f);  // Bottom Right Of The Texture and Quad
		glTexCoord2f(1.0f, 1.0f); glVertex3f( .5f,  .5f, -.5f);  // Top Right Of The Texture and Quad

		// Bottom Face
		glTexCoord2f(1.0f, 1.0f); glVertex3f(-.5f, -.5f, -.5f);  // Top Right Of The Texture and Quad
		glTexCoord2f(0.0f, 1.0f); glVertex3f( .5f, -.5f, -.5f);  // Top Left Of The Texture and Quad
		glTexCoord2f(0.0f, 0.0f); glVertex3f( .5f, -.5f,  .5f);  // Bottom Left Of The Texture and Quad
		glTexCoord2f(1.0f, 0.0f); glVertex3f(-.5f, -.5f,  .5f);  // Bottom Right Of The Texture and Quad

		// Right face
		glTexCoord2f(1.0f, 0.0f); glVertex3f( .5f, -.5f, -.5f);  // Bottom Right Of The Texture and Quad
		glTexCoord2f(1.0f, 1.0f); glVertex3f( .5f,  .5f, -.5f);  // Top Right Of The Texture and Quad
		glTexCoord2f(0.0f, 1.0f); glVertex3f( .5f,  .5f,  .5f);  // Top Left Of The Texture and Quad
		glTexCoord2f(0.0f, 0.0f); glVertex3f( .5f, -.5f,  .5f);  // Bottom Left Of The Texture and Quad

		// Left Face
		glTexCoord2f(0.0f, 0.0f); glVertex3f(-.5f, -.5f, -.5f);  // Bottom Left Of The Texture and Quad
		glTexCoord2f(1.0f, 0.0f); glVertex3f(-.5f, -.5f,  .5f);  // Bottom Right Of The Texture and Quad
		glTexCoord2f(1.0f, 1.0f); glVertex3f(-.5f,  .5f,  .5f);  // Top Right Of The Texture and Quad
		glTexCoord2f(0.0f, 1.0f); glVertex3f(-.5f,  .5f, -.5f);  // Top Left Of The Texture and Quad
	glEnd();
}

void init()
{
	// Set projection transform 
	glMatrixMode(GL_PROJECTION);
	glLoadIdentity(); 
	//glOrtho(-1.0,1.0,-1.0,1.0,-1.0,1.0);
	glOrtho(-10.0f, 10.0f, -10.0f, 10.0f, -10.0f, 10.0f);

	// Set view transform 
	glMatrixMode(GL_MODELVIEW); 
	glLoadIdentity(); 
	gluLookAt(1.0, 1.0, 1.0, 0.0, 0.0, 0.0, 0.0, 1.0, 0.0);

	Image* image = loadBMP("vtr.bmp");
	_textureId = loadTexture(image);
	delete image;
}

void display(){
	glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

	//glTranslatef(0.0, 0.0, -5.0);
	//glRotatef(angle, 1.0, 1.0, 1.0);
	drawCube(10.0);
}


int main( int agrc, char* args[] )
{
	SDL_Init(SDL_INIT_EVERYTHING);
	SDL_Surface* screen=SDL_SetVideoMode(600,400,32, SDL_SWSURFACE|SDL_OPENGL );
	bool running = true;
	Uint32 start;
	SDL_Event event;
	init();

	while(running)
	{
		start=SDL_GetTicks();
		while(SDL_PollEvent(&event))
		{
			switch(event.type)
			{
				case SDL_QUIT:
					running = false;
					break;
			}
		}
		display();
		SDL_GL_SwapBuffers();
		angle+=0.1;
		if(angle > 360)
			angle -= 360;
		if(1000/30>(SDL_GetTicks()-start))
			SDL_Delay(1000/30>(SDL_GetTicks()-start));
	}

	SDL_FreeSurface(screen);
	SDL_Quit();
	return 0;}


RESULT:
Posted Image


WARNING: You need the required "vtr.bmp" to make this code work. You can use any size as long as it's a power of two.


What I did wrong:
I changed glOrtho and I got it work now. The values I used previously were wrong.






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