Right down to business, basically I am making a small mini game which has characters running on top of a flat clock with the clock hand rotating around, the characters have to avoid it by jumping.
the part im struggling with is coding the collision, the clock hand is just a set model that is rotated applying matrices and for whatever reason box collision will not work.
So my theory is because i know the angle that the clock hand is currently being multiplied by, is there some mathematical way to calculate the angle of the player in relation to the centre point of the circle so that this can be checked against the clock hand angle?
Sure.
float angle = atan2(y_handle - y_center, x_handle - x_center);
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I am trying to make a game in space with Newtonian physics. I am trying to make an object (spaceship) increase its rotation speed when WASD keys are pressed. I used a vec3 to represent rotation speed for each axis. My problem is, how to calculate the rotation speed in respect to the coordinate system when I only know the speed I want in relation to my object (spaceship)?
In other words, my player is looking through the object. I want to go rotate left relative to him when he presses A, but I don't know how to calculate it in relation to the universe (coordinate system).
So, I'm a high school student and the lead programmer on my local robotics team, and this year I decided to try out OpenCV and do some vision processing on our robot.
From my vision code, I need to know a few things about some objects on our competition field. These things are: distance (ft), horizontal angle from camera, and horizontal distance from camera (ft). Essentially, one large right triangle.
I already have the camera successfully detecting these objects and putting a boundingRect around them. With a gyroscope on our robot, we should be able to get our robot to ~90 degree angle to the object once it is detected (as it's a set angle on the field). Thus, I can calculate distance just based on an empirically made function of the area of the boundingRect of the object.
The horizontal angle of the object from the camera, however, I'm not exactly sure how to approach. Once I have that, though, I can do some simple trig and get the horizontal distance.
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So here's what we have/know: Distance to object in ft, object is at ~90 degrees to camera, camera has horizontal fov of 67 degrees w/ resolution of 800x600, the real world dimensions of the object, and a boundingRect around the object.
How would I, using all of this information, calculate the horizontal angle from the camera to the object?
I have some questions for correctly implementing a system that add gravity to my player while still detecting and correcting collision with the floor. I understand the basic math for the AABB and adding gravity vector to the players velocity vector then adding it to the position. For some reason when I try the player stops for the first few frames then eventually the velocity builds up to be more than the tile width and it goes through. I guess my real question is how to properly implement the gravity with the collision. Do I make gravity vector 0, 0 when it hits the floor or when I am just standing on the floor my collision detection will constantly move me out of the floor? I really don't know the flow of the logic with this situation.
Edit 1:
I am trying to make the simple engine myself to gain experience with programming. I kind of solved the one problem, I now can stop on the floor. My current logic is:
add gravity to velocity, check for collision, adjust the velocity by the offset of the collision, if any, add velocity to the position then set velocity to 0.
m_velocity += m_gravity;
glm::vec2 mtd = collideWithObject(objectVector);
m_velocity -= mtd;
m_position += m_velocity;
m_velocity.x = 0.0f;
m_velocity.y = 0.0f;
It works but I am not sure if that is the flow, I guess I just want to know what is the most common way to implement this.
For some reason when I try the player stops for the first few frames then eventually the velocity builds up to be more than the tile width and it goes through.
If you are applying physics in increments - such as once every frame - you must account for the infinite increments that exist between each of those points.
For a simple "plane collision", like your floor, don't test if your current AABB collides with the floor. Create the smallest AABB that includes your current AABB and the last AABB. If that box collides, you've collided with the plane.
as #MorphingDragon mentioned, you should consider Box2D, many games use Box2D.
For your question "Do I make gravity vector 0, 0 when it hits the floor or when I am just standing on the floor my collision detection will constantly move me out of the floor? I really don't know the flow of the logic with this situation.". I just assume you know Verlet integration, for calculate your new position, you don't need to change your gravity, [as you know, gravity is everywhere on earth, or you want to do a game in space, ;)] you just need to handle the collision detection logic as "when collision happens, just make the collision point satisfy my constraints", and your constraint should be "all point should not be placed under the floor, otherwise just move it and make it sit on the floor".
The collection detection and constraint solver theory should be very common in modern physical engine and easy to understand and implement.
Hope this help.
Thanks
An
This is separate to a previous question I asked.
To make the collision detection simpler I am now using euclidean distance to work out if objects intersect.
I am working in a 3D environment using openGL with bounding walls around the
edges.
I have a player (just displayed as a quad for now)
There are also several randomly displayed cylinders acting as pillars, created using gluCylinder.
Intersection with the walls is fine, and I know that if there is an intersection with the left wall for example the player should be positioned at an X co ordinate that is 0.5 away from the bounding wall.That way if the player is going to go through the wall then it will have the appearance of being able to walk into the wall but not through it.
I am having trouble with the inner pillars, and what i should do with the player when i detect they are within a certain distance of a pillar.
I am using a euclidean distance calculation to detect collisions when diet is < than a value 1 for example.
double dist = sqrt(pow((playerX - xPosi[i]),2) + pow((playerZ - zPosi[i]),2));
xPosi[i] and zPosi[i] are arrays holding the x and z co ordinates of my pillars, and player X and Z hold the co ordinates of the player. Could anyone suggest how to handle the interaction with the pillars, as i now have the collision detection working.
The player will only be travelling in either a +ve or -ve x direction or +ve or -ve z direction, I would like the player to stop if a collision is detected and no longer be able to move through the pillar.
I am making a simple 3D OpenGL game. At the moment I have four bounding walls, a random distribution of internal walls and a simple quad cube for my player.
I want to set up collision detection between the player and all of the walls. This is easy with the bounding walls as i can just check if the x or z coordinate is less than or greater than a value. The problem is with the interior walls. I have a glGenList which holds small rectangular wall segments, at the initial setup i randomly generate an array of x,z co ordinates and translate these wall segments to this position in the draw scene. I have also added a degree of rotation, either 45 or 90 which complicates the collision detection.
Could anyone assist me with how I might go about detecting collisions here. I have the co ordinates for each wall section, the size of each wall section and also the co ordinates of the player.
Would i be looking at a bounded box around the player and walls or is there a better alternative?
I think your question is largely about detecting collision with a wall at an angle, which is essentially the same as "detecting if a point matches a line", which there is an answer for how you do here:
How can I tell if a point belongs to a certain line?
(The code may be C#, but the math behind it applies in any language). You just have to replace the Y in those formulas for Z, since Y appears to not be a factor in your current design.
There has been MANY articles and even books written on how to do "good" collision detection. Part of this, of course, comes down to a "do you want very accurate or very fast code" - for "perfect" simulations, you may sacrifice speed for accuarcy. In most games, of the players body "dents" the wall just a little bit because the player has gone past the wall intersection, that's perhaps acceptable.
It is also useful to "partition the space". The common way for this is "Binary space partitioning", which is nicely described and illustrated here:
http://en.wikipedia.org/wiki/Binary_space_partition
Books on game programming should cover basic principles of collision detection. There is also PLENTY of articles on the web about it, including an entry in wikipedia: http://en.wikipedia.org/wiki/Collision_detection
Short of making a rigid body physics engine, one could use point to plane distance to see if any of the cubes corner points are less than 0.0f away from the plane (I would use FLT_MIN so the points have a little radius to them). You will need to store a normalized 3d vector (vector of length 1.0f) to represent the normal of the plane. If the dot product between the vector from the center of the plane to the point and the plain normal is less than the radius you have a collision. After that, you can take the velocity (the length of the vector) of the cube, multiply it by 0.7f for some energy absorption and store this as the cubes new velocity. Then reflect the normalized velocity vector of the cube over the normal of the plane, then multiply that by the previously calculated new velocity of the cube.
If you really want to get into game physics, grab a pull from this guys github. I've used his book for a Physics for games class. There are some mistakes in the book so be sure to get all code samples from github. He goes through making a mass aggregate physics engine and a rigid body one. I would also brush up on matrices and tensors.