OpenSpace/src/util/powerscaledsphere.cpp

/*****************************************************************************************
*                                                                                       *
* OpenSpace                                                                             *
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* Copyright (c) 2014                                                                    *
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// open space includes
#include <openspace/util/powerscaledsphere.h>

#include <ghoul/logging/logmanager.h>

#define _USE_MATH_DEFINES
#include <math.h>

namespace {
const std::string _loggerCat = "PowerScaledSphere";
}

namespace openspace {

PowerScaledSphere::PowerScaledSphere(const PowerScaledScalar& radius, int segments)
    : _vaoID(0)
    , _vBufferID(0)
    , _iBufferID(0)
    , _mode(GL_TRIANGLES)
    , _isize(6 * segments * segments)
    , _vsize((segments + 1) * (segments + 1))
    , _varray(new Vertex[_vsize])
    , _iarray(new int[_isize])
{
    static_assert(sizeof(Vertex) == 64,
                  "The size of the Vertex needs to be 64 for performance");

    int nr = 0;
    const float fsegments = static_cast<float>(segments);
    const float r = static_cast<float>(radius[0]);

    for (int i = 0; i <= segments; i++) {
        // define an extra vertex around the y-axis due to texture mapping
        for (int j = 0; j <= segments; j++) {
            const float fi = static_cast<float>(i);
            const float fj = static_cast<float>(j);

            // inclination angle (north to south)
            const float theta = fi * float(M_PI) / fsegments;  // 0 -> PI

            // azimuth angle (east to west)
            const float phi = fj * float(M_PI) * 2.0f / fsegments;  // 0 -> 2*PI

            const float x = r * sin(phi) * sin(theta);  //
            const float y = r * cos(theta);             // up
            const float z = r * cos(phi) * sin(theta);  //

            glm::vec3 normal = glm::vec3(x, y, z);
            if (!(x == 0.f && y == 0.f && z == 0.f))
                normal = glm::normalize(normal);

            const float t1 = fj / fsegments;
            const float t2 = fi / fsegments;

            _varray[nr].location[0] = x;
            _varray[nr].location[1] = y;
            _varray[nr].location[2] = z;
            _varray[nr].location[3] = static_cast<GLfloat>(radius[1]);
            _varray[nr].normal[0] = normal[0];
            _varray[nr].normal[1] = normal[1];
            _varray[nr].normal[2] = normal[2];

            _varray[nr].tex[0] = t1;
            _varray[nr].tex[1] = t2;
            ++nr;
        }
    }

    nr = 0;
    // define indices for all triangles
    for (int i = 1; i <= segments; ++i) {
        for (int j = 0; j < segments; ++j) {
            const int t = segments + 1;
            _iarray[nr] = t * (i - 1) + j + 0;
            ++nr;
            _iarray[nr] = t * (i + 0) + j + 0;
            ++nr;
            _iarray[nr] = t * (i + 0) + j + 1;
            ++nr;

            _iarray[nr] = t * (i - 1) + j + 0;
            ++nr;
            _iarray[nr] = t * (i + 0) + j + 1;
            ++nr;
            _iarray[nr] = t * (i - 1) + j + 1;
            ++nr;
        }
    }
}

PowerScaledSphere::~PowerScaledSphere()
{
    delete[] _varray;
    delete[] _iarray;

    glDeleteBuffers(1, &_vBufferID);
    glDeleteBuffers(1, &_iBufferID);
    glDeleteVertexArrays(1, &_vaoID);
}

bool PowerScaledSphere::initialize()
{
    // Initialize and upload to graphics card
    GLuint errorID;
    if (_vaoID == 0)
        glGenVertexArrays(1, &_vaoID);

    if (_vBufferID == 0) {
        glGenBuffers(1, &_vBufferID);

        if (_vBufferID == 0) {
            LERROR("Could not create vertex buffer");
            return false;
        }
    }

    if (_iBufferID == 0) {
        glGenBuffers(1, &_iBufferID);

        if (_iBufferID == 0) {
            LERROR("Could not create index buffer");
            return false;
        }
    }

    // First VAO setup
    glBindVertexArray(_vaoID);

    glBindBuffer(GL_ARRAY_BUFFER, _vBufferID);
    glBufferData(GL_ARRAY_BUFFER, _vsize * sizeof(Vertex), _varray, GL_STATIC_DRAW);

    glEnableVertexAttribArray(0);
    glEnableVertexAttribArray(1);
    glEnableVertexAttribArray(2);
    glVertexAttribPointer(0, 4, GL_FLOAT, GL_FALSE, sizeof(Vertex),
                          reinterpret_cast<const GLvoid*>(offsetof(Vertex, location)));
    glVertexAttribPointer(1, 2, GL_FLOAT, GL_FALSE, sizeof(Vertex),
                          reinterpret_cast<const GLvoid*>(offsetof(Vertex, tex)));
    glVertexAttribPointer(2, 3, GL_FLOAT, GL_FALSE, sizeof(Vertex),
                          reinterpret_cast<const GLvoid*>(offsetof(Vertex, normal)));

    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _iBufferID);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, _isize * sizeof(int), _iarray, GL_STATIC_DRAW);

    glBindVertexArray(0);

    errorID = glGetError();
    if (errorID != GL_NO_ERROR) {
        LERROR("OpenGL error: " << glewGetErrorString(errorID));
        return false;
    }
    return true;
}

void PowerScaledSphere::render()
{
    glBindVertexArray(_vaoID);  // select first VAO
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, _iBufferID);
    glDrawElements(_mode, _isize, GL_UNSIGNED_INT, 0);
    glBindVertexArray(0);
}

}  // namespace openspace