Textures Missing

OpenGL OpenGL: Basic Coding
1

Hi!

I’m trying to add texture to a project I’m working on. But somehow no textures appear.
The project is really big so I’m just gonna post the parts I think are important to the textures. Please ask if you need more.


int main(int argc, char* argv[]){
	glutDisplayFunc(HandleDisplayCallback);
	world = new World();
	glutMainLoop();
	delete world;
	return 0;
}

World::World()
{
	cars[0] = new Car("model.3ds");
	terrain = new Terrain("Terrain.bmp");
}

void World::Draw()
{
	HandleKeyboard();
	terrain->Draw();
	cars[0]->Draw();
}

Terrain::Terrain(const char* terrainFileName_)
{
	sprintf(terrainFileName, "%s", terrainFileName_);
	LoadTextures();
	InitializeTerrain();
}


void Terrain::LoadTextures()
{ 
	glGenTextures(1, &t_relva); 
	perror("glGenTextures");
	glBindTexture(GL_TEXTURE_2D, t_relva); 
	perror("glBindTexture");
	sprintf(tPath, "%sgreen.bmp", TEX_PATH);
	imag.LoadBmpFile(tPath); 
	//imag.LoadBmpFile(TEX_PATH+"green.bmp");
	glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL); 
	perror("glTexEnvf");
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); 
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); 
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP); 
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP); 
	perror("glTexParameteri");
	glTexImage2D(GL_TEXTURE_2D, 0, 3,  
				 imag.GetNumCols(), 
				 imag.GetNumRows(), 0, GL_RGB, GL_UNSIGNED_BYTE, 
				 imag.ImageData()); 
	perror("glTexImage2D");
}

void Terrain::Draw(){
	// set the current texture to the land texture
	glBindTexture(GL_TEXTURE_2D, t_relva);
	//printf("Draw
");
	// we are going to loop through all of our terrain's data points,
	// but we only want to draw one triangle strip for each set along the x-axis.
	for (int z = 0; z < MAP_Z-1; z++)
	{
		glBegin(GL_TRIANGLE_STRIP);
		for (int x = 0; x < MAP_X-1; x++)
		{
			// for each vertex, we calculate the grayscale shade color, 
			// we set the texture coordinate, and we draw the vertex.
			/*
			 the vertices are drawn in this order:
			 
			 0  ---> 1
			 /
			 /
			 |/
			 2  ---> 3
			 */
			
			///printf("triangle strip: %d, %d, %d
", terrain[x][z][0], terrain[x][z][1], terrain[x][z][2]);
			// draw vertex 0
			glColor3f(terrain[x][z][1]/255.0f, terrain[x][z][1]/255.0f, terrain[x][z][1]/255.0f);
			glTexCoord2f(0.0f, 0.0f);
			glVertex3f(terrain[x][z][0], terrain[x][z][1], terrain[x][z][2]);
			
			// draw vertex 1
			glTexCoord2f(1.0f, 0.0f);
			glColor3f(terrain[x+1][z][1]/255.0f, terrain[x+1][z][1]/255.0f, terrain[x+1][z][1]/255.0f);
			glVertex3f(terrain[x+1][z][0], terrain[x+1][z][1], terrain[x+1][z][2]);
			
			// draw vertex 2
			glTexCoord2f(0.0f, 1.0f);
			glColor3f(terrain[x][z+1][1]/255.0f, terrain[x][z+1][1]/255.0f, terrain[x][z+1][1]/255.0f);
			glVertex3f(terrain[x][z+1][0], terrain[x][z+1][1], terrain[x][z+1][2]);
			
			// draw vertex 3
			glColor3f(terrain[x+1][z+1][1]/255.0f, terrain[x+1][z+1][1]/255.0f, terrain[x+1][z+1][1]/255.0f);
			glTexCoord2f(1.0f, 1.0f);
			glVertex3f(terrain[x+1][z+1][0], terrain[x+1][z+1][1], terrain[x+1][z+1][2]);
		}
		glEnd();
	}
	// enable blending
	glEnable(GL_BLEND);

}

I want to leave here a disclaimer, I did not do everything by myself but I understand all that is here.

2

The glEnable(GL_TEXTURE_2D); is missing from this snippet.

3

Thank you, thank you, thank you, thank you, thank you, thank you, thank you . . .

I put glEnable(GL_TEXTURE_2D); in the LoadTextures method and in the Terrain::Draw method. So now it’s like



void Terrain::LoadTextures()
{ 
	errno = 0;
	glEnable(GL_TEXTURE_2D);
	glGenTextures(1, &t_relva); 
	perror("glGenTextures");
	glBindTexture(GL_TEXTURE_2D, t_relva); 
	perror("glBindTexture");
	sprintf(tPath, "%sgreen.bmp", TEX_PATH);
	imag.LoadBmpFile(tPath); 
	//imag.LoadBmpFile(TEX_PATH+"green.bmp");
	glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL); 
	perror("glTexEnvf");
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR); 
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR); 
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP); 
	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP); 
	perror("glTexParameteri");
	glTexImage2D(GL_TEXTURE_2D, 0, 3,  
				 imag.GetNumCols(), 
				 imag.GetNumRows(), 0, GL_RGB, GL_UNSIGNED_BYTE, 
				 imag.ImageData()); 
	perror("glTexImage2D");
	glDisable(GL_TEXTURE_2D);
}

void Terrain::Draw(){
	glEnable(GL_TEXTURE_2D);
	// set the current texture to the land texture
	glBindTexture(GL_TEXTURE_2D, t_relva);
	//printf("Draw
");
	// we are going to loop through all of our terrain's data points,
	// but we only want to draw one triangle strip for each set along the x-axis.
	for (int z = 0; z < MAP_Z-1; z++)
	{
		glBegin(GL_TRIANGLE_STRIP);
		for (int x = 0; x < MAP_X-1; x++)
		{
			// for each vertex, we calculate the grayscale shade color, 
			// we set the texture coordinate, and we draw the vertex.
			/*
			 the vertices are drawn in this order:
			 
			 0  ---> 1
			 /
			 /
			 |/
			 2  ---> 3
			 */
			
			///printf("triangle strip: %d, %d, %d
", terrain[x][z][0], terrain[x][z][1], terrain[x][z][2]);
			// draw vertex 0
			glColor3f(terrain[x][z][1]/255.0f, terrain[x][z][1]/255.0f, terrain[x][z][1]/255.0f);
			glTexCoord2f(0.0f, 0.0f);
			glVertex3f(terrain[x][z][0], terrain[x][z][1], terrain[x][z][2]);
			
			// draw vertex 1
			glTexCoord2f(1.0f, 0.0f);
			glColor3f(terrain[x+1][z][1]/255.0f, terrain[x+1][z][1]/255.0f, terrain[x+1][z][1]/255.0f);
			glVertex3f(terrain[x+1][z][0], terrain[x+1][z][1], terrain[x+1][z][2]);
			
			// draw vertex 2
			glTexCoord2f(0.0f, 1.0f);
			glColor3f(terrain[x][z+1][1]/255.0f, terrain[x][z+1][1]/255.0f, terrain[x][z+1][1]/255.0f);
			glVertex3f(terrain[x][z+1][0], terrain[x][z+1][1], terrain[x][z+1][2]);
			
			// draw vertex 3
			glColor3f(terrain[x+1][z+1][1]/255.0f, terrain[x+1][z+1][1]/255.0f, terrain[x+1][z+1][1]/255.0f);
			glTexCoord2f(1.0f, 1.0f);
			glVertex3f(terrain[x+1][z+1][0], terrain[x+1][z+1][1], terrain[x+1][z+1][2]);
		}
		glEnd();
	}
	glDisable(GL_TEXTURE_2D);
	// enable blending
	glEnable(GL_BLEND);

}

Is this correct?
It works but am I putting too many times or maybe in strange places?

4

Just enabling once is enough (Obviously if you don’t call function glDisable with GL_TEXTURE_2D as param).

Remember OpenGL is a machine state, so if you change the state to enable GL_TEXTURE_2D the state won’t change until you change it.

5

And it is not needed in LoadTextures.
Only needed before actually drawing stuff.