I am working on a project for my openGL class that is supposed to emulate a Yo-Yo, I am making progress but I have seem to hit a roadblock when it comes to checking the bounds of the screen. I am trying to get it so that once the ball reaches the bottom of the screen it starts to go up and vice verse, and help would be much appreciated!
I have three static floats declared above that are to be incremented by the function, I am trying to check the deltay in order to limit the ball's movement.
Below is my function that translates the ball, the ball moves but will continue to move past the boundaries I have set
void moveYoYo()
{
glClear(GL_COLOR_BUFFER_BIT);
//going up
if(flag == 1)
{
deltay -= .05;
if(deltay <= -.002)
{
flag = 0;
}
}
//going down
if(flag == 0)
{
deltay += .05;
if(deltay >= .002)
{
flag = 1;
}
}
glPushMatrix();
glTranslatef(deltax,deltay,deltaz);
display();
glPopMatrix();
glFlush();
glutSwapBuffers();
}
If you want that ball to bounce between the bottom and the top of the screen, the lower bound where it changes the direction should be <= -0.002 and the upper bound >= 1.002 if you want to use those strange numbers. Anyway much better would be to use less random numbers, like f.e.:
if (flag == 1) {
// Going down
deltay -= 0.05f;
if (deltay == 0)
flag = 0;
} else if (flag == 0) {
// Going up
deltay += 0.05f;
if (deltay == 1)
flag = 1;
}
Also if the flag in only used as 0 or 1 why not use a bool?
Related
I tried making a simple bouncing ball with constant velocity, that is supposed to bounce of the screen edges.
I have succeeded in making the ball move forward and down, but it does not stop and instead keeps moving and goes out of the screen.
Also, I just started c++ graphics yesterday and the program is quite primitive and thus I'd appreciate it if the answer could be simple.
(All Header files are included)
void main()
{
int gdriver = DETECT, gmode, xmax, ymax, Vx=10, Vy=10, Cx=150, Cy=150, t=1;
initgraph(&gdriver, &gmode, "");
xmax = getmaxx();
ymax = getmaxy();
setfillstyle(SOLID_FILL, YELLOW);
a:
while((Cx!=xmax-5 && Cx!=0) || (Cy!=ymax-5 && Cy!=0))
{
Cx += (Vx * t);
Cy += (Vy * t);
clrscr();
pieslice(Cx,Cy,0,360,10);
delay(100);
}
if (Cx==xmax-5 || Cx==0)
{
Vx = - Vx;
}
else if (Cy==ymax-5 || Cy==0)
{
Vy = - Vy;
}
goto a;
}
while(Cx!=xmax-5 || Cx!=0 || Cy!=ymax-5 || Cy!=0)
This is always true!
Whatever the value of Cx, it is always either "not xmax-5" or "not zero" (well, unless xmax-5 itself is zero, which it is probably isn't).
Similarly, your Cy conditions always hold.
So, the ball always moves.
Instead:
while ((Cx!=xmax-5 && Cx!=0) || (Cy!=ymax-5 && Cy!=0))
Now you still have the problem that the horizontal and vertical movement is checked at once, which only works if the ball hits an exact corner. But I'll leave you to work that one out on your own.
I am kinda stuck with my basic voxel physics right now. It's very, very choppy and I am pretty sure my maths is broken somewhere, but let's see what you have to say:
// SOMEWHERE AT CLASS LEVEL (so not being reinstantiated every frame, but persisted instead!)
glm::vec3 oldPos;
// ACTUAL IMPL
glm::vec3 distanceToGravityCenter =
this->entity->getPosition() -
((this->entity->getPosition() - gravityCenter) * 0.005d); // TODO multiply by time
if (!entity->grounded) {
glm::vec3 entityPosition = entity->getPosition();
if (getBlock(floorf(entityPosition.x), floorf(entityPosition.y), floorf(entityPosition.z))) {
glm::vec3 dir = entityPosition - oldPos; // Actually no need to normalize as we check for lesser, bigger or equal to 0
std::cout << "falling dir: " << glm::to_string(dir) << std::endl;
// Calculate offset (where to put after hit)
int x = dir.x;
int y = dir.y;
int z = dir.z;
if (dir.x >= 0) {
x = -1;
} else if (dir.x < 0) {
x = 1;
}
if (dir.y >= 0) {
y = -1;
} else if (dir.y < 0) {
y = 1;
}
if (dir.z >= 0) {
z = -1;
} else if (dir.z < 0) {
z = 1;
}
glm::vec3 newPos = oldPos + glm::vec3(x, y, z);
this->entity->setPosition(newPos);
entity->grounded = true; // If some update happens, grounded needs to be changed
} else {
oldPos = entity->getPosition();
this->entity->setPosition(distanceToGravityCenter);
}
}
Basic idea was to determine from which direction entityt would hit the surface and then just position it one "unit" back into that direction. But obviously I am doing something wrong as that will always move entity back to the point where it came from, effectively holding it at the spawn point.
Also this could probably be much easier and I am overthinking it.
As #CompuChip already pointed out, your ifs could be further simplified.
But what is more important is one logical issue that would explain the "choppiness" you describe (Sadly you did not provide any footage, so this is my best guess)
From the code you posted:
First you check if entity is grounded. If so you continue with checking if there is a collision and lastly, if there is not, you set the position.
You have to invert that a bit.
Save old position
Check if grounded
Set the position already to the new one!
Do collision detection
Reset to old position IF you registered a collision!
So basically:
glm::vec3 distanceToGravityCenter =
this->entity->getPosition() -
((this->entity->getPosition() - gravityCenter) * 0.005d); // TODO multiply by time
oldPos = entity->getPosition(); // 1.
if (!entity->grounded) { // 2.
this->fallingStar->setPosition(distanceToGravityPoint); // 3
glm::vec3 entityPosition = entity->getPosition();
if (getBlock(floorf(entityPosition.x), floorf(entityPosition.y), floorf(entityPosition.z))) { // 4, 5
this->entity->setPosition(oldPos);
entity->grounded = true; // If some update happens, grounded needs to be changed
}
}
This should get you started :)
I want to elaborate a bit more:
If you check for collision first and then set position you create an "infinite loop" upon first collision/hit as you collide, then if there is a collision (which there is) you set back to the old position. Basically just mathematic inaccuracy will make you move, as on every check you are set back to the old position.
Consider the if-statements for one of your coordinates:
if (dir.x >= 0) {
x = -1;
}
if (dir.x < 0) {
x = 1;
}
Suppose that dir.x < 0. Then you will skip the first if, enter the second, and x will be set to 1.
If dir.x >= 0, you will enter the first if and x will be set to -1. Now x < 0 is true, so you will enter the second if as well, and x gets set to 1 again.
Probably what you want is to either set x to 1 or to -1, depending on dir.x. You should only execute the second if when the first one was not entered, so you need an else if:
if (dir.x >= 0) {
x = -1;
} else if (dir.x < 0) {
x = 1;
}
which can be condensed, if you so please, into
x = (dir.x >= 0) ? -1 : 1;
I am trying to make a shooter game, and while trying to code the enemies
to face towards the player, I tried to use trigonometry to find the necessary rotation, but the code didn't work, and the enemy rotated erratically. This is the code:
void face(sf::Sprite& target, sf::Sprite& subject){
int adjacent = subject.getPosition().x - target.getPosition().x;
int opposite = target.getPosition().y - subject.getPosition().y;
if (opposite == 0){
opposite++;
}
if (adjacent == 0){
adjacent++;
}
//if (adjacent < 0){
//adjacent += 180;
//}
float result=atan(/*opposite / adjacent*/adjacent/opposite)*180/PI;
subject.setRotation(result);
}
Any advice would be appreciated!
You must use float with adjacent and opposite. And change result with this:
float angle = atan(adjacent / opposite) * 180 / PI;
if (opposite > 0)
angle += 180;
I have a problem with my 2d platformer. As i have just started out with c++ i'm having trouble with tile collision. I'm able to prevent the player from entering the tile and also being able to move away from it but somehow he cant move along the tile.
This is the function for checking if the new position is inside a solid tile:
void Maps::drawColMap(Player& _player){
for (int i = 0; i < _player.tiles.size(); i++)
{
if (colMap[_player.tiles[i].y][_player.tiles[i].x] == 1) //solid tile = 1
{
_player.willCollide = true;
break;
}
else {
_player.willCollide = false;
}
}
}
And here is the code for moving the player:
void Player::update()
{
sf::Vector2f newPosition;
sf::Vector2f oldPosition;
oldPosition.x = playerImage.getPosition().x; // store the current position
oldPosition.y = playerImage.getPosition().y;
newPosition.x = playerImage.getPosition().x; // store the new position
newPosition.y = playerImage.getPosition().y;
if (sf::Keyboard::isKeyPressed(sf::Keyboard::Left))
{
source.y = Left; //sprite stuff
moving = true;
newPosition.x -= 2;
}
if (sf::Keyboard::isKeyPressed(sf::Keyboard::Right))
{
source.y = Right;
moving = true;
newPosition.x += 2;
}
if (sf::Keyboard::isKeyPressed(sf::Keyboard::Up))
{
source.y = Up;
moving = true;
newPosition.y -= 2;
}
if (sf::Keyboard::isKeyPressed(sf::Keyboard::Down))
{
source.y = Down;
moving = true;
newPosition.y += 2;
}
if (!(sf::Keyboard::isKeyPressed(sf::Keyboard::Left) || sf::Keyboard::isKeyPressed(sf::Keyboard::Right) || sf::Keyboard::isKeyPressed(sf::Keyboard::Up) || sf::Keyboard::isKeyPressed(sf::Keyboard::Down)))
{
moving = false;
}
//create corners to check collision
bottom = newPosition.y + 32; //tile size is 32 px
left = newPosition.x;
right = newPosition.x + 32;
top = newPosition.y;
sf::Vector2i topLeft(sf::Vector2i((int)left / 32, (int)top / 32)); // get the corners of the new position
sf::Vector2i topRight(sf::Vector2i((int)right / 32, (int)top / 32));
sf::Vector2i bottomLeft(sf::Vector2i((int)left / 32, (int)bottom / 32));
sf::Vector2i bottomRight(sf::Vector2i((int)right / 32, (int)bottom / 32));
tiles.clear();
tiles.push_back(topLeft);
if (std::find(tiles.begin(), tiles.end(), topRight) == tiles.end()) tiles.push_back(topRight); //check the corners
if (std::find(tiles.begin(), tiles.end(), bottomLeft) == tiles.end()) tiles.push_back(bottomLeft);
if (std::find(tiles.begin(), tiles.end(), bottomRight) == tiles.end()) tiles.push_back(bottomRight);
//if no collision set the position to the new position
if (!willCollide)
playerImage.setPosition(newPosition);
else
playerImage.setPosition(oldPosition); //if collision then set the position to the previous position
}
Any help is appreciated!
//edit 1
I tried logging the collision and it says that the player is still in the collision area even if i dont press anything. But how do i prevent the player from entering? I cant find the problem.
//edit 2
I think i found another problem.
The collision check should probably be run just before moving the player and after moving the new position.
After the player collides, and you change the positions, move it over by 1 pixel in the away from the collision area (the appropriate direction). It's possible that your corner is still within the collision bounds if it wasn't moved out of of the collision area properly.
I am working on an SFML game and for some reason after spawning the player, the player gets teleported down. On the first tick he is correctly positioned, but after wards, he is moved down. Any idea on how to diagnose this problem? I set up breakpoints in the move mechanism, the only place where the player's co-ordinates change, and it seems to happen right after the function ends. This is the main function:
int main(){
App.ShowMouseCursor(false);
mainch.mainchinventory.read();
while (App.IsOpened())
{
sf::Event Event;
while (App.GetEvent(Event))
{
if (Event.Type == sf::Event::Closed)
App.Close();
}
float time = App.GetFrameTime();
mainch.move(time);
App.Clear();
drawall();
App.Display();
}
return EXIT_SUCCESS;
}
Mainch.move(t):
void cmainchar::move(float t){
if (App.GetInput().IsKeyDown(sf::Key::S)) mainchinventory.save();
if (App.GetInput().IsKeyDown(sf::Key::R)) mainchinventory.read();
if (App.GetInput().IsKeyDown(sf::Key::A)) A = true;
else A = false;
if (App.GetInput().IsKeyDown(sf::Key::D)) D = true;
else D = false;
if(grounded)
if (App.GetInput().IsKeyDown(sf::Key::W)) first = true;
if ((App.GetInput().IsKeyDown(sf::Key::I)) && (keyreleased)){
if (mainchinventory.drawmain){
mainchinventory.drawmain = false;
mainchinventory.press(mainchinventory.selectionx, 3);
}
else{
mainchinventory.drawmain = true;
}
keyreleased = false;
}
else if (!App.GetInput().IsKeyDown(sf::Key::I))
keyreleased = true;
if(!mainchinventory.drawmain){
if(App.GetInput().IsKeyDown(sf::Key::Num1)) mainchinventory.press(0, 3);
else if(App.GetInput().IsKeyDown(sf::Key::Num2)) mainchinventory.press(1, 3);
else if(App.GetInput().IsKeyDown(sf::Key::Num3)) mainchinventory.press(2, 3);
else if(App.GetInput().IsKeyDown(sf::Key::Num4)) mainchinventory.press(3, 3);
else if(App.GetInput().IsKeyDown(sf::Key::Num5)) mainchinventory.press(4, 3);
else if(App.GetInput().IsKeyDown(sf::Key::Num6)) mainchinventory.press(5, 3);
else if(App.GetInput().IsKeyDown(sf::Key::Num7)) mainchinventory.press(6, 3);
else if(App.GetInput().IsKeyDown(sf::Key::Num8)) mainchinventory.press(7, 3);
else if(App.GetInput().IsKeyDown(sf::Key::Num9)) mainchinventory.press(8, 3);
else if(App.GetInput().IsKeyDown(sf::Key::Num0)) mainchinventory.press(9, 3);
if(App.GetInput().IsMouseButtonDown(sf::Mouse::Button::Left)){
mainchinventory.dockitems[mainchinventory.selectionx].use();
spells.push_back(cspell());
}
}
else if ((App.GetInput().IsMouseButtonDown(sf::Mouse::Button::Left)) && (mainchinventory.drawmain) && (buttonreleased)){
mainchinventory.checkmouse();
buttonreleased = false;
}
else if (!App.GetInput().IsMouseButtonDown(sf::Mouse::Button::Left))
buttonreleased = true;
int xmap = (View.GetCenter().x - 320) / 40;
int ymap = (View.GetCenter().y - 240) / 40;
if ((xmap != xmapold) || (ymap != ymapold))
maps.read();
xmapold = xmap;
ymapold = ymap;
collisions();
for(std::list<cspell>::iterator i = mainch.spells.begin(); i != mainch.spells.end(); i++)
if (i->move(t))
spells.erase(i);
if (A && left){
animate(2, t);
you.Move(-160 * t, 0);
}
if (D && right){
animate(1, t);
you.Move(160 * t, 0);
}
if (!D && !A)
animate(0, t);
if (up){
if(grounded && first){
jump = 1.25;
first = false;
}
if (jump > 0){
you.Move (0,-250 * t * jump);
jump = jump - 1 * t;
}
if (jump <= 0){
jump = 0.f;
}
}
else{
first = false;
jump = 0.f;
}
if (down){
fall = fall + 10 * t;
you.Move(0, 25 * fall * t);
grounded = false;
}
else{
fall = 0.f;
grounded = true;
}
if(teleport){
mainchinventory.spawn = true;
fall = 0.f;
jump = 0.f;
maps.changemap(maps.nxtmap);
teleport = false;
}
moveview();
}
You don't show the code where you're manipulating the sf::Sprite object, so I (or anyone else, really) can't say for certain, but...that said, I have a strong guess as to what's happening.
I've been familiarizing myself with SFML recently, too, and I encountered this issue myself. What I think is happening is you're calling sf::Sprite::Move(x,y) to move the sprite to position (x,y). This is incorrect; what you should be calling is sf::Sprite::SetPosition(x,y). (Both these functions take will take a 2d vector as an argument instead, btw).
I'm operating under the assumption you're using SFML 1.6, yes? Looks that way...version 2.0 changes the API somewhat, so in case you're using that Sprite::Move() becomes Sprite::move() and Sprite::SetPosition() becomes Sprite::setPosition().
Anyways, to wrap this up: the difference between Move(x,y) and SetPosition(x,y) is that Move adjusts the sprite's position relative to its current position, whereas SetPosition moves the sprite to a new position regardless of where it was before.
Again, this is a blind guess since the relevant code was not included...so was my shot in the dark correct?
Unfortunately, you haven't provided enough code for a straightforward diagnosis. With what you provided however, my best guess is that your fall variable hasn't been initialized. If it hasn't been initialized, its values can be completely random, likely being much larger than expected. This would explain your 'teleporting' behavior.