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zeeman86

OpenGL Wrong size of a cube

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zeeman86    122
Hi! I'm new to OpenGL but it works :) I've build a small scene with a rotation cube in the middle. The cube moves away, turn 90° and return to its starting position. This move and the loading of the textures works great. My problem is, that the size of the cube itself is a little bit crazy. As you can see in the code, I build it with a width of 4 and a height of 3. This result in an cube with an aspect rotation of 4:3 (Top and bottom 3:3). The strange thing is that I get a cube with an aspect rotation of ~1.2 or ~1.44, regarding my openglwindow. (And not the estimated 1.33) I guess the problem is the glViewport. As far as I can guess (I tried around a little bit), the Viewport is reset by LoadIdentity. I also tried a glViewport after the LoadIdentity with differen parameters. Always (with a viewport after loadidentity) I get a black screen with no cube (heaven knows where it is). Only with glViewPort(0.0f,0.0f,...) after the LoadIdentity I get the cube. But it is scaled to fill the whole window. Maybe someone can give me a hind or something like this. Here's the code:
void TSlideshow3D::initializeGL() {
/*Build everything up*/
	rtZ = -11.50f;
	rtX = 0.0f;
	rtY = 0.0f;
	rtOffsetZ = -0.10f * config->use3DSpeed;   //use3DSpeed is atm always 1.0f
	rtOffsetX = 0.50f * config->use3DSpeed;
	rtOffsetY = 1.05f * config->use3DSpeed;
}

void TSlideshow3D::resizeGL( int w, int h ) {
	if (h==0)			// Prevent A Divide By Zero By
	{
		h=1;		        // Making Height Equal One
	}

	glViewport(0, 0, w, h);		// Reset The Current Viewport
	glMatrixMode(GL_PROJECTION);	// Select The Projection Matrix
	glLoadIdentity();		// Reset The Projection Matrix

	// Calculate The Aspect Ratio Of The Window
	gluPerspective(45.0f,(GLfloat)w/(GLfloat)h,0.1f,100.0f);   //doesn't affect anything

	glMatrixMode(GL_MODELVIEW);		// Select The Modelview Matrix
	glLoadIdentity();			// Reset The Modelview Matrix
}

//Der Foto-Klotz wird erstellt
void TSlideshow3D::buildCube() {
	float width =4.0f;
	float height=3.0f;
	glBindTexture(GL_TEXTURE_2D, texture[ front ]);		// Select Our Texture
	glBegin(GL_QUADS);
	// Front Face					x	y	z
		glTexCoord2f(0.0f, 0.0f); glVertex3f(-width, -height,  width);	// Bottom Left Of The Texture and Quad
		glTexCoord2f(1.0f, 0.0f); glVertex3f( width, -height,  width);	// Bottom Right Of The Texture and Quad
		glTexCoord2f(1.0f, 1.0f); glVertex3f( width,  height,  width);	// Top Right Of The Texture and Quad
		glTexCoord2f(0.0f, 1.0f); glVertex3f(-width,  height,  width);	// Top Left Of The Texture and Quad
	glEnd();
/*and so on*/
	glBindTexture(GL_TEXTURE_2D, texture[ left ]);				// Select Our Texture
	glBegin(GL_QUADS);
	// Left Face
		glTexCoord2f(0.0f, 0.0f); glVertex3f(-width, -height, -width);	// Bottom Left Of The Texture and Quad
		glTexCoord2f(1.0f, 0.0f); glVertex3f(-width, -height,  width);	// Bottom Right Of The Texture and Quad
		glTexCoord2f(1.0f, 1.0f); glVertex3f(-width,  height,  width);	// Top Right Of The Texture and Quad
		glTexCoord2f(0.0f, 1.0f); glVertex3f(-width,  height, -width);	// Top Left Of The Texture and Quad
	glEnd(); 

}


void TSlideshow3D::paintGL() {

   glClear(GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT);

  glLoadIdentity();                             // Reset The View

 	glTranslatef(0.0f ,0.0f, rtZ);               // Move Camera
 		
 	glRotatef(rtX, 0.0f,1.0f,0.0f);               // Rotate
 	glRotatef(rtY, 1.0f,0.0f,0.0f);
	this->buildCube();
 
/*Some controlling of the position of the cube.
Adjusting the rtOffsets depending on the position*/


	rtZ += rtOffsetZ;
	rtX += rtOffsetX;
	rtY += rtOffsetY;
}


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MARS_999    1627
I am not sure what you are after but the only thing I can think of is change your gluPerspective angle from 45 to 90.0 and see what happens...

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