As an avid Game Maker user for 1.5 years now, I've run into quite a few problems that are rarely if ever addressed by tutorials or documentation. This post will hopefully be the first of many to address some of the problems I've come across and how I've solved them. If you're using Game Maker to craft your own game, or even if you are using another engine, I hope you find this helpful. Now, on to today's problem...
Problem:
I want my character to walk up and down angled slopes, but my character just collides with things and then stops, even if it's only a 1 degree incline! Help!
This problem can be handled in many ways, but the easiest I've found is to use what I've dubbed an "angle sweep". In simple terms, your character will, every step, check a number of points at various angles in front of it to determine where it can walk.
How do we do that? Luckily for you, I've written a script to take care of it! I've included two versions. One has a ton of comments to explain exactly what the script is doing, and the other doesn't.
I've written out the script below so you can see what you're getting yourself into before you download, and I've included a video so you can see the script in action. Have fun!
/////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////
// Script: Walking up/down slopes.
// Written by Seth Coster of Stoz Studios (www.stozstudios.com)
// Paste this into a script named something like "scr_Walk".
// Call this script in the key presses of your character which are for movement.
// When calling the script, use scr_Walk("left") to move left, and scr_Walk("right") to move right.
// Note: This script assumes the character has a variable called "movespeed" which determines how many pixels the character moves at a time. Use 10 as your base movespeed and tweak it from there.
// First we check which direction to walk.
if argument0 = "left" {
dir = -1
}
else if argument0 = "right" {
dir = 1
}
// Now that we have the direction, it's time to do the angle sweep. Since this will occur in a loop, it sweeps over a crapload of angles every step.
anglesweep = -90+40*dir; // This is the starting point of the sweep, in degrees.
anglerem = 100; // We're going to use a 100-degree sweep.
pathclear = 0; // "pathclear" is a toggle switch. If we find a path to walk, it gets set to "1" and we break the loop.
while (anglerem >= 0 && pathclear = 0){
anglesweep += 5*dir; // We're doing 5-degree jumps in our sweep.
anglerem -= 5; // Decrease "anglerem" by the degrees in each angle interval.
// Using the lengthdir function, we grab the x,y coordinates of the target location found for the current angle.
groundspotx = x+lengthdir_x(movespeed,anglesweep)
groundspoty = y+lengthdir_y(movespeed,anglesweep)
// Then, we check if the spot is free and if there's ground beneath it.
if place_free(groundspotx,groundspoty) && !place_free(groundspotx,groundspoty+5)
pathclear = 1 // If so, HOORAY! The path is clear for walking. If not, "pathclear" will stay at 0 and the loop will end after checking its 100 degree sweep.
}
// The loop is now finished. Time to check if we have clear ground to walk on, and if we are already on the ground.
if (pathclear == 1 && !place_free(x,y+1)){
// First, change the character's X and Y coordinates to the destination.
x+=lengthdir_x(movespeed,anglesweep)
y+=lengthdir_y(movespeed,anglesweep)
move_contact_solid(270,15) // This will drop the character to contact with the ground if he ended up a few pixels above it.
vspeed = 0 // Not required, but useful at times.
hspeed = 0 // Not required , but useful at times.
}
// If we failed the "path clear" test, we check to see if we're airborne. If so, we just move right/left in midair.
else if place_free(x+lengthdir_x(movespeed, 90-90*dir), y)
x += dir*max(movespeed-abs(hspeed), 0)
// Last if we aren't airborne and have no clear path to walk, we'll just move to contact the closest solid obstacle.
else{
move_contact_solid(90-90*dir, max(movespeed-abs(hspeed), 0))
movingleft = 0
movingright = 0
}
/////////////////////////////////////////////////////////
/////////////////////////////////////////////////////////
// COMMENT-FREE VERSION
// Script: Walking up/down slopes.
// Written by Seth Coster of Stoz Studios (www.stozstudios.com)
// Paste this into a script named something like "scr_Walk".
// Call this script in the key presses of your character which are for movement.
// When calling the script, use scr_Walk("left") to move left, and scr_Walk("right") to move right.
// Note: This script assumes the character has a variable called "movespeed" which determines how many pixels the character moves at a time. Use 10 as your base movespeed and tweak it from there.
if argument0 = "left" {
dir = -1
}
else if argument0 = "right" {
dir = 1
}
anglesweep = -90+40*dir;
anglerem = 100;
pathclear = 0;
while (anglerem >= 0 && pathclear = 0){
anglesweep += 5*dir;
anglerem -= 5;
groundspotx = x+lengthdir_x(movespeed,anglesweep)
groundspoty = y+lengthdir_y(movespeed,anglesweep)
if place_free(groundspotx,groundspoty) && !place_free(groundspotx,groundspoty+5)
pathclear = 1
}
if (pathclear == 1 && !place_free(x,y+1)){
x+=lengthdir_x(movespeed,anglesweep)
y+=lengthdir_y(movespeed,anglesweep)
move_contact_solid(270,15)
vspeed = 0
hspeed = 0
}
else if place_free(x+lengthdir_x(movespeed, 90-90*dir), y)
x += dir*max(movespeed-abs(hspeed), 0)
else{
move_contact_solid(90-90*dir, max(movespeed-abs(hspeed), 0))
movingleft = 0
movingright = 0
}
