Terrain Generation

^^create a 64 x 64 block, no need to place in room. keep default room dimensions 1024 x 768. this all means we have a grid of 1024 / 64 = 16 block spaces x 768 / 64 = 12 block spaces to work with

Creation Code (for room0):

//max / min height (in blocks):
maxHeight = 9;
minHeight = 3;
	
//to calculate height and width of grid, got to
//spawn an instance of the block first:
temp = instance_create_layer(0,0,"Instances",objBlock); 
  blockHeight = objBlock.sprite_height;
  blockWidth = objBlock.sprite_width;
  gridHeight = room_height / blockHeight;
  gridWidth = room_width / blockWidth;
instance_destroy(temp);

//co-ords for our first block:
randomize();
xx = 0;
yy = irandom_range(gridHeight - maxHeight, gridHeight - minHeight);
	
//go across the screen...
for(columnToFill = xx; columnToFill <= gridWidth; columnToFill += 1){
	//... work out up one, same height or down one for each column...
	upSameDown = irandom_range(1,3); //1 up, 2 same height, 3 down
	switch(upSameDown){
	  case 1: if(yy > (gridHeight - maxHeight))yy -= 1; break;
	  case 2: break; //do nothing - same height!
	  case 3: if(yy < (gridHeight - minHeight))yy += 1; break;
	}
		
	//...and fill each column to the ground:
	for(columnPos = yy; columnPos <= gridHeight; columnPos += 1){
	 instance_create_layer(columnToFill * blockWidth, columnPos * blockHeight, "Instances", objBlock);
	}
}

Creation Code (for game maker 8.1 lite users):

//max / min height (in blocks):
maxHeight = 9;
minHeight = 3;

//to calculate height and width of grid, got to
//spawn an instance of the block first:
temp = instance_create(0,0,objBlock); 
  blockHeight = objBlock.sprite_height;
  blockWidth = objBlock.sprite_width;
  gridHeight = room_height / blockHeight;
  gridWidth = room_width / blockWidth;
with (temp) instance_destroy();

//co-ords for our first block:
randomize();
xx = 0;
yy = irandom_range(gridHeight - maxHeight, gridHeight - minHeight);

//go across the screen...
for(columnToFill = xx; columnToFill <= gridWidth; columnToFill += 1){
//... work out up one, same height or down one for each column...
  upSameDown = irandom_range(1,3); //1 up, 2 same height, 3 down
  switch(upSameDown){
    case 1: if(yy > (gridHeight - maxHeight))yy -= 1; break;
    case 2: break; //do nothing - same height!
    case 3: if(yy < (gridHeight - minHeight))yy += 1; break;
  }

  //...and fill each column to the ground:
  for(columnPos = yy; columnPos <= gridHeight; columnPos += 1){
   instance_create(columnToFill * blockWidth, columnPos * blockHeight, objBlock);
  }
}