glm::vec2 WorldToScreen(glm::mat4 viewMatrix,
      glm::mat4 projectionMatrix, glm::vec3 point)
{
 glm::mat4 mvpmatrix = projectionMatrix * viewMatrix;
 const float *pSource = (const float *)glm::value_ptr(mvpmatrix);
 glm::vec4 clipCoords;
 clipCoords.x = point.x * pSource[0] + point.y * pSource[4] + point.z * pSource[8] + pSource[12];
 clipCoords.y = point.x * pSource[1] + point.y * pSource[5] + point.z * pSource[9] + pSource[13];
 clipCoords.z = point.x * pSource[2] + point.y * pSource[6] + point.z * pSource[10] + pSource[14];
 clipCoords.w = point.x * pSource[3] + point.y * pSource[7] + point.z * pSource[11] + pSource[15];

 glm::vec3 normalizedDeviceCoordinates;
 normalizedDeviceCoordinates.x = clipCoords.x / clipCoords.w;
 normalizedDeviceCoordinates.y = clipCoords.y / clipCoords.w;
 normalizedDeviceCoordinates.z = clipCoords.z / clipCoords.w;

 GLint viewport[4] = {0};
 glGetIntegerv(GL_VIEWPORT, viewport); // viewport = (0, 0, width, height)

 glm::vec3 winPos;
 winPos.x = (viewport[2] / 2 * normalizedDeviceCoordinates.x) + (normalizedDeviceCoordinates.x + viewport[2] / 2);
 winPos.y = -(viewport[3] / 2 * normalizedDeviceCoordinates.y) + (normalizedDeviceCoordinates.y + viewport[3] / 2);
 winPos.z = 0;

 return winPos;
}

glm::vec3 ScreenToWorld(glm::mat4 viewMatrix, glm::mat4 projectionMatrix, glm::vec2 point)
{
 GLfloat winX, winY, winZ;
 GLint viewport[4] = {0};
 glGetIntegerv(GL_VIEWPORT, viewport); // viewport = (0, 0, width, height)

 winX = (float)point.x;
 winY = (float)viewport[3] - (float)point.y;
 glReadPixels(point.x, int(winY), 1, 1, GL_DEPTH_COMPONENT, GL_FLOAT, &winZ);

 glm::vec3 ret = glm::unProject(glm::vec3(winX, winY, winZ), viewMatrix, projectionMatrix, glm::vec4(viewport[0], viewport[1], viewport[2], viewport[3]));
 return ret;
}