How to draw a line based on an angle with a defined size?

[Genesys Generation]

I have a game where the player shoots a projectile based on the mouse direction when clicking, which travels 500 pixels.

I wish I could draw a line exactly where the projectile will be destroyed.

What I can do is draw a line from where the projectile is created to where the mouse is when it is clicked.

That is, the line may be longer or shorter than the path taken by the projectile.

The code is something like this:

draw_line(x,y,mouse_x,mouse_y);

Result in game:



Below an image explaining:



These blue dots would be the click of the mouse. That no matter where it went, the line drawn (green) would be the same (ending in pink x).

I know how to get the direction and how to calculate the distance, but I don't know how to implement it in line drawing.

 

[Catastrophe]

lengthdir_x
lengthdir_y

Spoiler

dir = point_direction(x,y,mouse_x,mouse_y)
draw_line(x,y,x + lengthdir_x(500,dir), y+ lengthdir_y(500,dir))

should do the trick

 

[Yal]

lengthdir_x
lengthdir_y

Spoiler

dir = point_direction(x,y,mouse_x,mouse_y)
draw_line(x,y,x + lengthdir_x(500,dir), y+ lengthdir_y(500,dir))

should do the trick

It might look more natural to end the line at mouse coordinates if it's less than 500, so it's effectively capped off at 500 but will otherwise go to the mouse but not any longer:

Spoiler

dist = point_distance(x,y,mouse_x,mouse_y)
if(dist > 500){
dir = point_direction(x,y,mouse_x,mouse_y)
draw_line(x,y,x + lengthdir_x(500,dir), y+ lengthdir_y(500,dir))
}
else{
draw_line(x,y,mouse_x,mouse_y)
}

(You might wanna replace all the "500"s with the name of the variable you store the distance in, of course... just using a 500 here since that's what the distance is in your gorgeous explanatory graph)

 

[CloseRange]

It might look more natural to end the line at mouse coordinates if it's less than 500, so it's effectively capped off at 500 but will otherwise go to the mouse but not any longer:

Spoiler

dist = point_distance(x,y,mouse_x,mouse_y)
if(dist > 500){
dir = point_direction(x,y,mouse_x,mouse_y)
draw_line(x,y,x + lengthdir_x(500,dir), y+ lengthdir_y(500,dir))
}
else{
draw_line(x,y,mouse_x,mouse_y)
}

it would look much better but neither are exactly what they asked. He wants the point where the projectile is destroyed. This means at most 500 pixels away and at least when it hits an object. That means implementing ray casting, now's the time where I put in my code on how to do that:

Spoiler: My code

nah, I'm too lazy

 

[Catastrophe]

xD Well TBF he didn't strictly ask for that, he just talked about effective range.

In that case, you'll need to do collision_line_list (ordered set to true) on anything that your bullet can collide with and then just the line to the first thing. Easy if everything a bullet collides with is parented to a single object, annoying if not.

 

[Yal]

He does say this at the very end of the post, though.

I know how to get the direction and how to calculate the distance, but I don't know how to implement it in line drawing.

I suppose clamping the line to 500 instead of a variable was taking the images too literally (I'll go fix that now), but he's actually asking about only the line-drawing bit.

 

[Genesys Generation]

Using trigonometry I was able to solve my problem.

Calcle:

seno=dsin(point_direction(x,y,mouse_x,mouse_y));
cose=dcos(point_direction(x,y,mouse_x,mouse_y));

Draw:

draw_line(x,y,x+(500*cose),y+(-500*seno));

 

[Joe Ellis]

You can just use a vector instead of needing to deal with angles\trigonometry:

var d = 500 / point_distance(x, y, mouse_x, mouse_y);

draw_line(x, y, x +( (mouse_x - x) * d), y + ((mouse_y - y) * d)

The vector is: mouse_pos - pos

Then you can get the normal by normalizing it (dividing the vector by the length\distance of it)

Then multiply it by 500 or however long you want the line to be.

(The 500 / point_distance part is shortening the process, cus normally it would be 1 / length of vector, but would then get multiplied by 500 after, so you can just do it then and there instead)