skybox.cpp

c++程序

// SkyBox.cpp: Implementierung der Klasse CSkyBox.
//
//////////////////////////////////////////////////////////////////////

#include "stdafx.h"
#include "SkyBox.h"

//////////////////////////////////////////////////////////////////////
// Konstruktion/Destruktion
//////////////////////////////////////////////////////////////////////

CSkyBox::CSkyBox()
{

}

CSkyBox::~CSkyBox()
{

}

void CSkyBox::DrawSkyBox(float fXRotation, float fYRotation, 
						 unsigned int iFOV, float fSkyBrightness, float fAspect)
{
	// Draw skybox

	// Convert degrees to texture coordinates
	fYRotation /= 150.0f;
	fXRotation /= 100.0f;

	// Use skybox texture
	m_SkyBoxTexture.Use();
	
	// Brightness
	glColor3f(fSkyBrightness, fSkyBrightness, fSkyBrightness);

	// Save fog, depth buffer, lighting and texture bit
	glPushAttrib(GL_FOG_BIT | GL_DEPTH_BUFFER_BIT | GL_TEXTURE_BIT |
		         GL_LIGHTING_BIT);

		// Disable fog
		glDisable(GL_FOG);

		// Disable lighting
		glDisable(GL_LIGHTING);

		// Disable updating and testing the depth buffer
		glDisable(GL_DEPTH_TEST);

		// Set correct texture parameters for moving skybox
		glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S, GL_REPEAT);
		glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_T, GL_REPEAT);

		// Distance of the skybox to the camera
		const float fDistance = -1.0f;

		// Project the quad into a 2D plane that covers the whole screen

		float fLowerLeft[3];
		float fLowerRight[3];
		float fUpperLeft[3];
		float fUpperRight[3];

		Project2D(-1.0f, -1.0f, fDistance, iFOV, fAspect, fLowerLeft);
		Project2D(1.0f, -1.0f, fDistance, iFOV, fAspect, fLowerRight);
		Project2D(-1.0f, 1.0f, fDistance, iFOV, fAspect, fUpperLeft);
		Project2D(1.0f, 1.0f, fDistance, iFOV, fAspect, fUpperRight);
	
		// Draw quad for the skybox
		glBegin(GL_QUADS);
			glTexCoord2f(0.0f - fYRotation, 0.0f - fXRotation);
			glVertex3fv(fLowerLeft);
			glTexCoord2f(1.0f - fYRotation, 0.0f - fXRotation);
			glVertex3fv(fLowerRight);
			glTexCoord2f(1.0f - fYRotation, 1.0f - fXRotation);
			glVertex3fv(fUpperRight);
			glTexCoord2f(0.0f - fYRotation, 1.0f - fXRotation);
			glVertex3fv(fUpperLeft);
		glEnd();

	glPopAttrib();
}

void CSkyBox::Project2D(const float fU, const float fV, const float fPlane,
						const unsigned int iFOV, float fAspect, float fVertex3DOut[3])
{
	// Project a point in 2D space. The point in 2D space is normalized. 
	// Lower-left corner is -1,-1 and upper-right is +1,+1

	fVertex3DOut[2]= fPlane;
	fVertex3DOut[1] =- tanf(iFOV * 0.5f * 6.283185f / 360.0f ) * fVertex3DOut[2];
	fVertex3DOut[0]= fVertex3DOut[1] * fAspect * fU;
	fVertex3DOut[1] *= fV;
}