Texture mapping - Opengl

OpenGL OpenGL: Basic Coding
1

Hi,

I have started to explore Opengl and I’m facing a problem with texture mapping. I have created a simple program just to see how texture mapping is working(and then I will hopefully create a solar system with texture on planets) and then having the lines of code below I getting the folowing errors

…

GLubyte rgb = {255, 255, 255, 0, 0, 0, 0, 0, 0, 255, 255,255};

glTexImage2D(GL_TEXTURE_2D, 0, 3, teximageWidth,teximageHeight,0, GL_RGB, GL_UNSIGNED_BYTE, rgb);

…

Error 1 too many initializers
Error 2’glTexImage2D’ : cannot convert parameter 9 from ‘GLubyte’ to ‘const GLvoid *’

The error 1 is for the rgb and error 2 for the glTexImage2D. I don’t know if you want any other code or all the code if you want just tell me…

Thanks

2

Make rgb an array. Second error even says it’s not an array, but of GLubyte type.

3

I have make it an array…but I think I have bigger errors now which I don’t understand them :slight_smile:

Error 1 error LNK2019: unresolved external symbol “unsigned char * __cdecl TextureLoadBitmap(char *,int *,int *)” (?TextureLoadBitmap@@YAPAEPADPAH1@Z) referenced in function “void __cdecl myinit(void)” (?myinit@@YAXXZ)

Error 2 fatal error LNK1120: 1 unresolved externals

4

Looks like you only included the header file for TextureLoadBitmap in your project. Try including the source file and/or linking with a library that implements it.

N.

5

I’m sorry but I don’t understand you well. Can you explain me in more details please.

Thanks

6

If you receive an error code that you don’t understand, the best way to solve it is by doing a google search for the error code or check the msdn documentation.

An unresolved symbol means that you have provided a function ( most likely in a header file like texture.h) but you didn’t provide a definition/implementation for it (this should be in your texture.cpp or texture.c file).

Make sure that you included the source file for compilation in the project or that you linked to a dll file that implements the
TextureLoadBitmap function.

N.

7

I understand, you mean to have all the classes (glut.h…) in the include folder of the visual studio. I have them…Ok this is my code…I may have some unnecessary things is ok…

#include <GL/glut.h>
#include <stdio.h>
#include <windows.h>

int y=500;
int x=500;

GLubyte rgb[12] = {255, 255, 255, 0, 0, 0, 0, 0, 0, 255, 255, 255};
GLubyte* TextureLoadBitmap(char* filename, int *w, int *h);
int teximageWidth = 2, teximageHeight = 2;
GLubyte *teximage;

void display(void){

glEnable(GL_TEXTURE_2D);
glTexImage2D(GL_TEXTURE_2D, 0, 3, teximageWidth,teximageHeight, 0, GL_RGB, GL_UNSIGNED_BYTE, rgb);
glBegin(GL_POLYGON);
	glTexCoord2f(0.0, 0.0); glVertex2f(0,0);
	glTexCoord2f(1.0, 0.0); glVertex2f(1,0);
	glTexCoord2f(1.0, 1.0); glVertex2f(0,1);
	glTexCoord2f(0.0, 1.0); glVertex2f(1,1);
glEnd();
glDisable(GL_TEXTURE_2D);

glEnable(GL_TEXTURE);
	glTexImage2D(GL_TEXTURE_2D, 0, 3,teximageWidth, teximageHeight, 0,GL_RGB, GL_UNSIGNED_BYTE, teximage);
glDisable(GL_TEXTURE);

}

void myinit()
{
teximage = TextureLoadBitmap(“test.bmp”,&teximageWidth, &teximageHeight);
glPixelStorei(GL_UNPACK_ALIGNMENT, 1);
glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_REPEAT);
glTexEnvf(GL_TEXTURE_ENV,GL_TEXTURE_ENV_MODE, GL_MODULATE);

}

int main(int argc, char **argv)
{
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DOUBLE | GLUT_DEPTH);
glutInitWindowSize(y,x);
glutCreateWindow(“TEXTURE”);
glEnableClientState(GL_VERTEX_ARRAY);
myinit();
glutDisplayFunc(display);
glEnable(GL_DEPTH_TEST);
glutMainLoop();
}

8

There’s just too much wrong with this code:

glutInitWindowSize(y,x); -> why not (x,y) unless you have some weird coordinate system?

glEnableClientState(GL_VERTEX_ARRAY); -> why?

glEnable(GL_DEPTH_TEST); -> you never clear it…

GLubyte* TextureLoadBitmap(char* filename, int *w, int *h); -> you didn’t implement it, you can’t expect the application to magically produce an image object just because you wrote this line of code.

glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_REPEAT); -> GL_TEXTURE_WRAP_T not repeating?

void display(void) -> you never generated an opengl texture, nor did you bind it to the GL_TEXTURE_2D state. Also, you should load a texture only once, not everytime something needs to be drawn on screen.

It’s best to start with some basic OpenGL examples such as these. Good luck! :wink:

N.

9

I’m very Sorry NiCo :)…

I’m a beginner I just copy paste codes just to see how they work and try to understand them

Thanks

10

No need to be sorry… I hope you get the hang of it soon.
Happy coding :slight_smile:

N.