I have a lunar lander type game. I don't use any physics engines.
My lander keeps falling if you do not use thruster and eventually lands on the ground. Ground is hand drawn, it is not a line, more like curve, and the land can be of any configuration or color.
How do I properly use collision detection and its results?
Well it depends on what you want to do. I would recommend one of the following:
Use physics engines. They are there for something. You could create different shapes what was drawn. You could mix in a rectangle if theres a straight line, or a lot of circles for curves, etc.
Use your own custom circle collision detector. You represent the lander with a bounding box sized circle. Then, for each of the handdrawn lines, create a bunch of adjacent circles representing the line. When you check your lander position, you are just basically looping through the circles representing the lines and checking for collisions. Incoming pseudocode
for (CollisionCircle* circle in collisions)
{
if (circle.collidesWith(lander.collisionCircle))
{
// 1. Calculate edge distance from lander to circle (position + radius distance)
// 2. Remove distance from lander position to fix position.
}
}
Related
I'm trying to convert a polygonal 3D mesh into a series of topographic curves that represent the part of the mesh at a specific height for every interval. So far, I've come up with the idea to intersect a horizontal plane with the mesh and get the intersection curve(s). So for this mesh:
I'd intersect a plane repeatedly at a set interval of precision:
and etc.
While this is straightforward to do visually and in a CAD application, I'm completely lost doing this programmatically. How could I achieve calculating this in a programming environment/ what algorithms can I look into to achieve this?
I'm programming in an STL C++ environment (with Boost), loading .obj meshes with this simple loader, and need simple cartesian 2D points to define the output curve.
An option is to process all the faces in turn and for every face determine the horizontal planes that traverses them. For a given plane and face, check all four vertexes in turn and find the changes of sign (of Zvertex - Zplane). There will be exactly two such changes, defining an edge that belongs to a level curve. (Exceptionally you can find four changes of sign, which occurs when the facet isn't planar - join the points in pairs.)
Every time you find an intersection point, you tag it with the (unique) index of the plane and the (unique) index of the edge that was intersected; you also tag it with the index of the other edge that was intersected in that face.
By sorting on the plane index, you can group the intersections per plane.
For a given plane, using a hash table, you can follow the chain of intersections, from edge to edge.
This gives you the desired set of curves.
I plan on making a game, and I want to create some background animations for said game. One of these animations is a rotating rectangle. I've looked all over, and I cannot find any form of math or logic that allows me to rotate a rectangle (SDL_Rect to be specific, but you might have already known that).
I can't figure out the math for myself, I really don't have any working code for this, so I can't show anything.
Essentially I'm looking for some type of logic that I can apply the rectangle's coordinates so that whenever the main game loop loops, it will rotate the rectangle some amount of degrees.
You can't rotate an SDL_Rect. If you look at its definition, it's made of coordinates for the top-left corner, the width and the height. There's no way to represent a rectangle with sides that aren't parallel to the coordinate system's axes.
SDL_RenderCopyEx supports drawing rotated textures, though.
Suppose the polygon is a hexagon.
To fill it gradiently, assume there are many smaller hexagons inside.
The smaller the hexagon, the pixel on that hexagon has a brighter color.
However, after I finish it, I find that there are spurious star edges between the center and the corners, like in the attached image (ignore the two discs inside).
How should I design an algorithm to make the filling more smoothly?
As the title describes, I want to make a tiny circle that circulates on the edge of the sector of the another big circle. I have implemented sector of the circle, now only issue here is how to make small circle circulate on the edge of this sector. I have tried various ways, however, none of them was proved to be successful, therefore I plead you to give me some tips of how to implement it.
Thanks in advance.
You just have to consider that, for a circle of radius 1 centered on the origin, every point on the circle can be described as:
P = [sin(alpha); cos(alpha)]
With 0<=alpha<2*pi
Now, if you change the radius and the center you will have:
P = [(radius * sin(alpha))+x_center; (radius*cos(alpha))+y_center]
So, just have a loop for alpha going from 0 to 2*pi (or whatever section of circle you need) and use the above equation to calculate the position of the center of the small circle.
I presume you have a a function that can draw a circle at a given position in cartesian co-ordinates and radius.
Use polar co-ordinates (angle / radius), set the radius to the radius of the big circle minus the small circle. Set the angle to wherever you want to start the circle. Then set a loop up to increment the angle by a given amount. After each increment, clear the screen, draw the big circle. Then convert the polar co-orindates into cartesian, add on the centre of the big circle and draw the small circle. Hold for as long as you want.
I want to detect if ellipse collides with another ellipse and rectangle. How I can do it?
I'm writing in C++. I want to use it for a game.
If this is for a game, then exactness should not be an issue.
Treat your ellipse as a polygon, that is, choose N evenly distributed points on your ellipse and treat is as a polygon. Adjuct N to the level of the desired correctness.
Now you need to test if a convex polygon collides with a rectangle. And the latter is a convex polygon as well. Here's a link for convex polygon collision detection
If you need precise answer, than you have to describe your figures as functions and use Newton's method for finding intersection points