int Camera::getHorizIntersectionFromScreenSpace(const glm::vec2& ndcClick, glm::vec2& result) {
// this first part finds the intersection of your ray with the horizontal z = 0 plane, whether in front of you
// or behind you.
glm::vec4 rayClip = getProjInv() * glm::vec4(ndcClick.x, ndcClick.y, -1.f, 1.f);
glm::vec4 rayWorld = getViewInv() * glm::vec4(rayClip.x, rayClip.y, -1.f, 0.f);
if (rayWorld.z) {
glm::vec4 ray = glm::normalize(rayWorld);
if (ray.x) {
float slopeX = ray.z / ray.x;
result.x = eye.x + (-eye.z / slopeX);
} else {
result.x = eye.x;
}
if (ray.y) {
float slopeY = ray.z / ray.y;
result.y = eye.y + (-eye.z / slopeY);
} else {
result.y = eye.y;
}
}
// the rest is to make sure the ray actually hits the horizontal plane (not the horizon) and that
// it hits somewhere in the camera's field of view (that it hits in front of you)
int clickedSkyOrGround = (rayWorld.z > 0) - (rayWorld.z < 0); // results 1 for sky, -1 for ground, 0 for horizon
int cameraAboveOrBelow = (eye.z > 0) - (eye.z < 0); // results 1 for above horizon, -1 for below, 0 for horizon
if (cameraAboveOrBelow) {
if (cameraAboveOrBelow == -clickedSkyOrGround) {
return clickedSkyOrGround;
} else {
return 0;
}
} else {
return 0;
}
// so finally, it returns 1 if you hit the horizontal plane from below (meaning the z = 0 plane was your sky)
// or -1 if you hit the same z = 0 plane from above (you hit the ground)
// or 0 if you never hit the z = 0 plane (like if you are above it and also shoot above it,
// or you shoot the horizon line or something.
}
std::vector<glm::vec3> kore::Camera::getWSfrustumCorners() {
glm::mat4 matViewInv = getViewInv();
// calculate frustum corner coordinates
float fFov2 = getFovRad() / 2.0f;
float tanFov2 = glm::tan(fFov2);
float h2Far = tanFov2 * _fFar;
float h2Near = tanFov2 * _fNear;
float hFar = 2.0f * h2Far;
float hNear = 2.0f * h2Near;
const glm::ivec2& res =
kore::RenderManager::getInstance()->getRenderResolution();
float aspect = static_cast<float>(res.x) / static_cast<float>(res.y);
float w2Far = (hFar * aspect) / 2.0f;
float w2Near = (hNear * aspect) / 2.0f;
glm::vec3 v3Corners[8];
v3Corners[0] = glm::vec3(-1.0f * w2Near, -1.0f * h2Near, -_fNear); // lbn
v3Corners[1] = glm::vec3(1.0f * w2Near, -1.0f * h2Near, -_fNear); // rbn
v3Corners[2] = glm::vec3(1.0f * w2Near, 1.0f * h2Near, -_fNear); // rtn
v3Corners[3] = glm::vec3(-1.0f * w2Near, 1.0f * h2Near, -_fNear); // ltn
v3Corners[4] = glm::vec3(-1.0f * w2Far, -1.0f * h2Far, -_fFar); // lbn
v3Corners[5] = glm::vec3(1.0f * w2Far, -1.0f * h2Far, -_fFar); // rbn
v3Corners[6] = glm::vec3(1.0f * w2Far, 1.0f * h2Far, -_fFar); // rtn
v3Corners[7] = glm::vec3(-1.0f * w2Far, 1.0f * h2Far, -_fFar); // ltn
std::vector<glm::vec3> vReturnCorners;
// transform each corner into WS
for (int i = 0; i < 8; ++i) {
glm::vec4 v4Result = matViewInv * glm::vec4(v3Corners[ i ], 1.0f);
vReturnCorners.push_back(glm::vec3(v4Result.x, v4Result.y, v4Result.z));
}
return vReturnCorners;
}
