SimpleEarth/src/Atmosphere.cpp at master · MAPSWorks/SimpleEarth · GitHub

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* The Simple Earth Project

* Author: Hector Mendoza, hector.mendoza@huesoftllc.com

* This file is part of the Simple Earth Project.

* The Simple Earth Project is free software: you can redistribute it

* and/or modify it under the terms of the GNU Lesser General Public

* License as published by the Free Software Foundation, either version

* 3 of the License, or (at your option) any later version.

* This program is distributed in the hope that it will be useful,

* but WITHOUT ANY WARRANTY; without even the implied warranty of

* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

* Lesser General Public License for more details.

* You should have received a copy of the GNU Lesser General Public

* License along with this program. If not, see

* <http://www.gnu.org/licenses/>.

#include <QtOpenGL>

#include "Atmosphere.h"

#include "Camera.h"

#include "Constants.h"

#include "Utilities.h"

static Camera* camera = NULL;

//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

/**

* Constructor. Initializes attributes.

Atmosphere::Atmosphere()

//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

{

camera = Camera::getInstance();

mTextureHandle = 0;

}

//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

/**

* Destructor.

Atmosphere::~Atmosphere()

//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

{

}

//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

/**

* Sets the atmosphere texture.

* @param handle OpenGL handle to texture

void Atmosphere::setTexture(unsigned int handle)

//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

{

mTextureHandle = handle;

}

//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

/**

* Builds the geometry and renders the atmosphere. The way we render the

* atmosphere could not be more simple. It is just a semi-transparent texture

* that gets drawn in front of the Earth and that provides the visual effect of

* atmospheric scattering.

void Atmosphere::render()

//++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

{

glPushMatrix();

GeodeticPosition cameraPosition = camera->getGeodeticPosition();

SimpleVector cameraXYZPosition = Utilities::geodeticToXYZ(cameraPosition);

float cameraRadius = cameraPosition.altitude + Constants::EARTH_MEAN_RADIUS;

//calculate image position so that it is always in front of the earth

float x = (cameraXYZPosition.x/cameraRadius) * 7000.0f;

float y = (cameraXYZPosition.y/cameraRadius) * 7000.0f;

float z = (cameraXYZPosition.z/cameraRadius) * 7000.0f;

glTranslatef(x, y, z);

//rotate image so that it always faces the camera

glRotatef(cameraPosition.longitude, 0.0f, 0.0f, 1.0f);

glRotatef(-cameraPosition.latitude, 0.0f, 1.0f, 0.0f);

//calculate image radius based on camera distance from

//center of the earth (camera radius)

float theta = atan(Constants::EARTH_MEAN_RADIUS/cameraRadius);

float adjacent = cameraRadius - Constants::EARTH_MEAN_RADIUS + 330.0f;

float textureSize = adjacent * tan(theta);//texture size is equal to the opposite side in a right triangle

textureSize *= 1.21f;//increment a little to account for image size

//enable texture transparency

glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_REPLACE);

glEnable(GL_BLEND);

glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);

glEnable(GL_TEXTURE_2D);

//get texture object id

glBindTexture(GL_TEXTURE_2D, mTextureHandle);

glBegin(GL_QUADS);

glTexCoord2f(0.0f, 0.0f);

glVertex3f(0.0f, -textureSize, -textureSize);

glTexCoord2f(1.0f, 0.0f);

glVertex3f(0.0f, textureSize, -textureSize);

glTexCoord2f(1.0f, 1.0f);

glVertex3f(0.0f, textureSize, textureSize);

glTexCoord2f(0.0f, 1.0f);

glVertex3f(0.0f, -textureSize, textureSize);

glEnd();

glDisable(GL_TEXTURE_2D);

glDisable(GL_BLEND);

glTexEnvi(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);

glPopMatrix();

}

SimpleEarth/src/Atmosphere.cpp at master · MAPSWorks/SimpleEarth · GitHub

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