I'm making a racecar game in OpenGL (just a small project) and I'm having problems trying to make my car follow the camera view.
It wasn't hard to make it follow the camera as the camera moves forward and/or backward, but as I rotate the camera (look right or left) the car remais still. I mean, it still moves forward and backward but it's not in front of the camera (it's on the side).
Here is my code (the part where I try to implement it):
void updateCam() {
gluLookAt(posX,posY + 0.025 * std::abs(sin(headPosAux*PI/180)),posZ,
posX + sin(roty*PI/180),posY + 0.025 * std::abs(sin(headPosAux*PI/180)) + cos(rotx*PI/180),posZ -cos(roty*PI/180),
0.0,1.0,0.0);
listenerPos[0] = posX;
listenerPos[1] = posY;
listenerPos[2] = posZ;
source0Pos[0] = posX;
source0Pos[1] = posY;
source0Pos[2] = posZ;
GLfloat distD;
distD = posZ - 3.3;
//makes the car "follow" the camera
modelPOR.Translate(posX,posY,distD);
}
I think the problem is that you change the center location in gluLookAt and not in the modelPOR.Translate
the 3 middle parameters of gluLookAt set the center of the view, so the car should be at the exact same position but you modify the center without modifying the car's position.
gluLookAt(posX,posY + 0.025 * std::abs(sin(headPosAux*PI/180)),posZ,
// center x
posX + sin(roty*PI/180),
// center y
posY + 0.025 * std::abs(sin(headPosAux*PI/180)) + cos(rotx*PI/180),
// center z
posZ -cos(roty*PI/180),
0.0,1.0,0.0);
you should probably translate the car by those same values. then it will be centered.
another problem that seems to be in that code is that you rotate the camera and not the car, so the car probably will not stay pointing in the same direction as the camera. (is that desired or do you do it elswhere?)
but are you really sure you want to make the car follow the camera? it would probably be better the other way around.
Related
I'm making a sniper shooter arcade style game in Gamemaker Studio 2 and I want the position of targets outside of the viewport to be pointed to by chevrons that move along the circumference of the scope when it moves. I am using trig techniques to determine the coordinates but the chevron is jumping around and doesn't seem to be pointing to the target. I have the code broken into two: the code to determine the coordinates in the step event of the enemies class (the objects that will be pointed to) and a draw event in the same class. Additionally, when I try to rotate the chevron so it also points to the enemy, it doesn't draw at all.
Here's the coordinate algorithm and the code to draw the chevrons, respectively
//determine the angle the target makes with the player
delta_x = abs(ObjectPlayer.x - x); //x axis displacement
delta_y = abs(ObjectPlayer.y - y); //y axis displacement
angle = arctan2(delta_y,delta_x); //angle in radians
angle *= 180/pi //angle in radians
//Determine the direction based on the larger dimension and
largest_distance = max(x,y);
plusOrMinus = (largest_distance == x)?
sign(ObjectPlayer.x-x) : sign(ObjectPlayer.y-y);
//define the chevron coordinates
chevron_x = ObjectPlayer.x + plusOrMinus*(cos(angle) + 20);
chevron_y = ObjectPlayer.y + plusOrMinus*(sign(angle) + 20);
The drawing code
if(object_exists(ObjectEnemy)){
draw_text(ObjectPlayer.x, ObjectPlayer.y-10,string(angle));
draw_sprite(Spr_Chevron,-1,chevron_x,chevron_y);
//sSpr_Chevron.image_angle = angle;
}
Your current code is slightly more complex that it needs to be for this, if you want to draw chevrons pointing towards all enemies, you might as well do that on spot in Draw. And use degree-based functions if you're going to need degrees for drawing anyway
var px = ObjectPlayer.x;
var py = ObjectPlayer.y;
with (ObjectEnemy) {
var angle = point_direction(px, py, x, y);
var chevron_x = px + lengthdir_x(20, angle);
var chevron_y = py + lengthdir_y(20, angle);
draw_sprite_ext(Spr_Chevron, -1, chevron_x, chevron_y, 1, 1, angle, c_white, 1);
}
(also see: an almost-decade old blog post of mine about doing this while clamping to screen edges instead)
Specific problems with your existing code are:
Using a single-axis plusOrMinus with two axes
Adding 20 to sine/cosine instead of multiplying them by it
Trying to apply an angle to sSpr_Chevron (?) instead of using draw_sprite_ext to draw a rotated sprite.
Calculating largest_distance based on executing instance's X/Y instead of delta X/Y.
I am a beginner in C++ and know SFML. I have read a lot of articles about Sprite rotation towards Mouse and have been able to calculate proper angle of rotation of Sprite using this code:
void Player::changeAngle(double Mx, double My) { // This is for making Player point towards Mouse
double dX = x - Mx; // x and y are global Varibales declared outside
double dY = y - My;
double magnitude = sqrt((dX*dX) + (dY*dY));
double normalizedX = dX / magnitude;
double normalizedY = dY / magnitude;
// This part is for Making Player move to Mouse
Xvelocity = normalizedX * speed; // Xvelocity, Yvelocity and speed are global variables
Yvelocity = normalizedY * speed;
// Rotate towards the Mouse
double angle = ( atan2(dY, dX) ) * 180 / M_PI;
entity.setRotation(angle); // entity is a sf::RectangleShape
}
And, this bit actually worked and the Sprite was rotating properly only before a few days. Now the Sprite is just frozen on the screen, nothing happens. I had not made any changes in that code but I had added a View from the main.cpp.
So here is how I call changeAngle() from the main.cpp :
case Event::MouseMoved : {
Vector2f worldPos = window.mapPixelToCoords(Mouse::getPosition(window), view);
double x = worldPos.x;
double y = worldPos.y;
player.changeAngle(x, y);
break;
}
I tried running the debugger and stepped through the code. I found that the angle is properly calculated and my mouse coordinates are also right. And, to my surprise, the sprite was Rotating now !
I could not understand why, but every time its in debugging mode, the Sprite will rotate. But, it won't rotate while running normally.
Can anyone tell me why and how to fix it so it rotates every time ? Tell me if there is any problem with my code.
Thanks !
So I nearly implemented a free-flight camera using vectors and something like gluLookAt.
The movement in all 4 directions and rotation around the Y-axis work fine.
For the rotation around the Y-axis I calculate the vector between the eye and center vector and then rotate it with the rotation matrix like this:
Vector temp = vecmath.vector(center.x() - eye.x(),
center.y() - eye.y(), center.z() - eye.z());
float vecX = (temp.x()*(float) Math.cos(-turnSpeed)) + (temp.z()* (float)Math.sin(-turnSpeed));
float vecY = temp.y();
float vecZ = (temp.x()*(float) -Math.sin(-turnSpeed))+ (temp.z()*(float)Math.cos(-turnSpeed));
center = vecmath.vector(vecX, vecY, vecZ);
At the end I just set center to the newly calculated vector.
Now when I try to do the same thing for rotation around the X-axis it DOES rotate the vector but in a very strange way, kind of like it would be moving in a wavy line.
I use the same logic as for the previous rotation, just with the x rotation matrix:
Vector temp = vecmath.vector(center.x() - eye.x(),
center.y() - eye.y(), center.z() - eye.z());
float vecX = temp.x();
float vecY = (temp.y()*(float) Math.cos(turnSpeed)) + (temp.z()* (float)-Math.sin(turnSpeed));
float vecZ = (temp.y()*(float) Math.sin(turnSpeed)) + (temp.z()*(float)Math.cos(turnSpeed));
center = vecmath.vector(vecX, vecY, vecZ);
But why does this not work? Maybe I do something else somewhere wrong?
The problem you're facing is the exact same that I had trouble with the first time I tried to implement the camera movement. The problem occurs because if you first turn so that you are looking straight down the X axis and then try to "tilt" the camera by rotating around the X axis, you will effectively actually spin around the direction you are looking.
I find that the best way to handle camera movement is to accumulate the angles in separate variables and every time rotate completely from origin. If you do this you can first "tilt" by rotating around the X-axis then turn by rotating around the Y-axis. By doing it in this order you make sure that the tilting will always be around the correct axis relative to the camera. Something like this:
public void pan(float turnSpeed)
{
totalPan += turnSpeed;
updateOrientation();
}
public void tilt(float turnSpeed)
{
totalTilt += turnSpeed;
updateOrientation();
}
private void updateOrientation()
{
float afterTiltX = 0.0f; // Not used. Only to make things clearer
float afterTiltY = (float) Math.sin(totalTilt));
float afterTiltZ = (float) Math.cos(totalTilt));
float vecX = (float)Math.sin(totalPan) * afterTiltZ;
float vecY = afterTiltY;
float vecZ = (float)Math.cos(totalPan) * afterTiltZ;
center = eye + vecmath.vector(vecX, vecY, vecZ);
}
I don't know if the syntax is completely correct. Haven't programmed in java in a while.
I'm implementing a first person camera using the GLM library that provides me with some useful functions that calculate perspective and 'lookAt' matrices. I'm also using OpenGL but that shouldn't make a difference in this code.
Basically, what I'm experiencing is that I can look around, much like in a regular FPS, and move around. But the movement is constrained to the three axes in a way that if I rotate the camera, I would still move in the same direction as if I had not rotated it... Let me illustrate (in 2D, to simplify things).
In this image, you can see four camera positions.
Those marked with a one are before movement, those marked with a two are after movement.
The red triangles represent a camera that is oriented straight forward along the z axis. The blue triangles represent a camera that hasbeen rotated to look backward along the x axis (to the left).
When I press the 'forward movement key', the camera moves forward along the z axis in both cases, disregarding the camera orientation.
What I want is a more FPS-like behaviour, where pressing forward moves me in the direction the camera is facing. I thought that with the arguments I pass to glm::lookAt, this would be achieved. Apparently not.
What is wrong with my calculations?
// Calculate the camera's orientation
float angleHori = -mMouseSpeed * Mouse::x; // Note that (0, 0) is the center of the screen
float angleVert = -mMouseSpeed * Mouse::y;
glm::vec3 dir(
cos(angleVert) * sin(angleHori),
sin(angleVert),
cos(angleVert) * cos(angleHori)
);
glm::vec3 right(
sin(angleHori - M_PI / 2.0f),
0.0f,
cos(angleHori - M_PI / 2.0f)
);
glm::vec3 up = glm::cross(right, dir);
// Calculate projection and view matrix
glm::mat4 projMatrix = glm::perspective(mFOV, mViewPortSizeX / (float)mViewPortSizeY, mZNear, mZFar);
glm::mat4 viewMatrix = glm::lookAt(mPosition, mPosition + dir, up);
gluLookAt takes 3 parameters: eye, centre and up. The first two are positions while the last is a vector. If you're planning on using this function it's better that you maintain only these three parameters consistently.
Coming to the issue with the calculation. I see that the position variable is unchanged throughout the code. All that changes is the look at point I.e. centre only. The right thing to do is to first do position += dir, which will move the camera (position) along the direction pointed to by dir. Now to update the centre, the second parameter can be left as-is: position + dir; this will work since the position was already updated to the new position and from there we've a point farther in dir direction to look at.
The issue was actually in another method. When moving the camera, I needed to do this:
void Camera::moveX(char s)
{
mPosition += s * mSpeed * mRight;
}
void Camera::moveY(char s)
{
mPosition += s * mSpeed * mUp;
}
void Camera::moveZ(chars)
{
mPosition += s * mSpeed * mDirection;
}
To make the camera move across the correct axes.
I'm trying to figure out how to make the camera in directx move based on the direction it's facing.
Right now the way I move the camera is by passing the camera's current position and rotation to a class called PositionClass. PositionClass takes keyboard input from another class called InputClass and then updates the position and rotation values for the camera, which is then passed back to the camera class.
I've written some code that seems to work great for me, using the cameras pitch and yaw I'm able to get it to go in the direction I've pointed the camera.
However, when the camera is looking straight up (pitch=90) or straight down (pitch=-90), it still changes the cameras X and Z position (depending on the yaw).
The expected behavior is while looking straight up or down it will only move along the Y axis, not along the X or Z axis.
Here's the code that calculates the new camera position
void PositionClass::MoveForward(bool keydown)
{
float radiansY, radiansX;
// Update the forward speed movement based on the frame time
// and whether the user is holding the key down or not.
if(keydown)
{
m_forwardSpeed += m_frameTime * m_acceleration;
if(m_forwardSpeed > (m_frameTime * m_maxSpeed))
{
m_forwardSpeed = m_frameTime * m_maxSpeed;
}
}
else
{
m_forwardSpeed -= m_frameTime * m_friction;
if(m_forwardSpeed < 0.0f)
{
m_forwardSpeed = 0.0f;
}
}
// ToRadians() just multiplies degrees by 0.0174532925f
radiansY = ToRadians(m_rotationY); //yaw
radiansX = ToRadians(m_rotationX); //pitch
// Update the position.
m_positionX += sinf(radiansY) * m_forwardSpeed;
m_positionY += -sinf(radiansX) * m_forwardSpeed;
m_positionZ += cosf(radiansY) * m_forwardSpeed;
return;
}
The significant portion is where the position is updated at the end.
So far I've only been able to deduce that I have horrible math skills.
So, can anyone help me with this dilemma? I've created a fiddle to help test out the math.
Edit: The fiddle uses the same math I used in my MoveForward function, if you set pitch to 90 you can see that the Z axis is still being modified
Thanks to Chaosed0's answer, I was able to figure out the correct formula to calculate movement in a specific direction.
The fixed code below is basically the same as above but now simplified and expanded to make it easier to understand.
First we determine the amount by which the camera will move, in my case this was m_forwardSpeed, but here I will define it as offset.
float offset = 1.0f;
Next you will need to get the camera's X and Y rotation values (in degrees!)
float pitch = camera_rotationX;
float yaw = camera_rotationY;
Then we convert those values into radians
float pitchRadian = pitch * (PI / 180); // X rotation
float yawRadian = yaw * (PI / 180); // Y rotation
Now here is where we determine the new position:
float newPosX = offset * sinf( yawRadian ) * cosf( pitchRadian );
float newPosY = offset * -sinf( pitchRadian );
float newPosZ = offset * cosf( yawRadian ) * cosf( pitchRadian );
Notice that we only multiply the X and Z positions by the cosine of pitchRadian, this is to negate the direction and offset of your camera's yaw when it's looking straight up (90) or straight down (-90).
And finally, you need to tell your camera the new position, which I won't cover because it largely depends on how you've implemented your camera. Apparently doing it this way is out of the norm, and possibly inefficient. However, as Chaosed0 said, it's what makes the most sense to me!
To be honest, I'm not entirely sure I understand your code, so let me try to provide a different perspective.
The way I like to think about this problem is in spherical coordinates, basically just polar in 3D. Spherical coordinates are defined by three numbers: a radius and two angles. One of the angles is yaw, and the other should be pitch, assuming you have no roll (I believe there's a way to get phi if you have roll, but I can't think of how currently). In conventional mathematics notation, theta is your yaw and phi is your pitch, with radius being your move speed, as shown below.
Note that phi and theta are defined differently, depending on where you look.
Basically, the problem is to obtain a point m_forwardSpeed away from your camera, with the right pitch and yaw. To do this, we set the "origin" to your camera position, obtain a spherical coordinate, convert it to cartesian, and then add it to your camera position:
float radius = m_forwardSpeed;
float theta = m_rotationY;
float phi = m_rotationX
//These equations are from the wikipedia page, linked above
float xMove = radius*sinf(phi)*cosf(theta);
float yMove = radius*sinf(phi)*sinf(theta);
float zMove = radius*cosf(phi);
m_positionX += xMove;
m_positionY += yMove;
m_positionZ += zMove;
Of course, you can condense a lot of this code, but I expanded it for clarity.
You can think about this like drawing a sphere around your camera. Each of the points on the sphere is a potential position in the next timestep, depending on the camera's rotation.
This is probably not the most efficient way to do it, but in my opinion it's certainly the easiest way to think about it. It actually looks like this is nearly exactly what you're trying to do in your code, but the operations on the angles are just a little bit off.