71² – The ramblings of two 30-something developers

mike  on June 4th, 2009

I’ve managed to work out why the volume was dropping off so quickly as well now. There are a number of settings which can define the type of operation you want to use for distance attenuation. I’ve not investigated them all yet, but you can add the following line of code to set a reference distance for a sound source and control how quickly the volume drops off as the sound source moves away from the listener.

alSourcef(sourceID, AL_REFERENCE_DISTNACE, 50.0f);

If you play with the value you will see how it effects the volume drop off.

From the documentation it would seem that for most needs in a 2D game the linear distance rolloff model would seem to be valid. This is where the volume drops off in a linear manner based on the distance from the source to the listener.

The command to set the model you want to use is

alDistanceModel(ALenum modelName);

Possible model names are:

AL_NONE
AL_INVERSE_DISTANCE
AL_INVERSE_DISTANCE_CLAMPED
AL_LINEAR_DISTANCE
AL_LINEAR_DISTANCE_CLAMPED
AL_EXPONENT_DISTANCE
AL_EXPONENT_DISTANCE_CLAMPED

There are also other options that can be set such as

AL_MAX_DISTANCE

which can be used to help tune the OpenAL model to your needs.

I’m making changes to the SoundManager at the moment and I’ll post the changes. The documentation at the following location has of course been useful ;o)

http://connect.creativelabs.co.....cation.pdf

Mike

A Person  on June 9th, 2009

Hey mike i gotten a lot of my collision detection class done and most of its working great except for layer collision detection so i can make layers a solid object if i want, i have object to object collision working great so here is my layer code which can get the collision for the second tile it hits (for some reason it skips the first) and it starts to move all jittery, the jiterryness can be fixed by giving a very very low speed but i still am not satisfied. So now the code.

- (void)detectCollisionForLayerNumber:(int)number rectObject:(Image*)objectOne speed:(CGPoint)speed delta:(float)delta direction:(int)direction {
	tileY = 0;
	tileX = 0;
	Layer *layer = [tiledMap.layers objectAtIndex:number];
	while(tileY < layer.layerHeight) {
		while(tileX < layer.layerWidth) {
			int globalID = [layer getGlobalTileIDAtX:tileX y:tileY];
			if(globalID != 0) {
				if([self rectObject:objectOne collisionWithRect:CGRectMake((tileX + 1) * [tiledMap tileWidth] - [tiledMap tileWidth], (tileY + 1) * [tiledMap tileHeight] - [tiledMap tileHeight], tiledMap.tileWidth, tiledMap.tileHeight)]) {
					if(direction == kDirection_Forward) {
						objectOne.origin = CGPointMake(objectOne.origin.x - speed.x * delta, objectOne.origin.y - speed.y * delta);
					} else if(direction == kDirection_Backwards) {
						objectOne.origin = CGPointMake(objectOne.origin.x + speed.x * delta, objectOne.origin.y + speed.y * delta);
					}
				}
			}
			tileX++;
		}
		tileY++;
		tileX = 0;
	}
}

This isn’t how i normally do this but i dont really care about doing anything else but stoping the object from going through that layer. Normally i return a yes or no and then i do what i what (that works). I’ve also tried getting info from the xml file without much success. I also made changes to the image class and tiledmap class to support what i’m doing for example origin and the layers array. These changes work and i’ve tried them multiple ways and it works but it keeps coming back to this method. No errors are given to me on build so if there is a ; missing or something its not that it was my copy and paste error.

Hope you can help mike and thanks for the great work you already been doing

A Person  on June 9th, 2009

sorry mike i don’t know what happened but i used the code but it didn’t work

A Person  on June 9th, 2009

i meant the code tag (i typed and it dissapeared)

A Person  on June 9th, 2009

I think I see my mistake I have to use the actually map point in there some where not to hard to figure out.

mike  on June 9th, 2009

@A Person, thanks for the comment. I’ve not had a chance to look through your code in detail yet, but I’ll check it out later.

What I tend to do with the tile map is set a property on tile images which should block the player, something like blocked = true.

When I load up the tile map I then run through the properties for each tile in the map and creation a collision map which is just an array that stores either a 0 or 1 for each tile in the map. If the map tile blocks then the array is 1 else it is 0.

When I am then moving the player, I convert the players pixel coordinates into a tile map, simply by dividing the pixel location by the tilewidth/height etc. If that shows that moving the player would place them in a blocked tile I reverse the movement and leave them where they were.

Doing this is very simple and has worked well in the past. I’ll take a look at your code a little later.

Mike

A Person  on June 10th, 2009

Thanks mike that’s actually what I did on my first go at this so I’ll revisit it and see what wasn’t working.

A Person  on June 13th, 2009

Hey mike its me again and same for the same thing.

I still can’t get the tiledMap layer collision detection to work and i’ve tried many ways but it seems to be that the tile map is rendered by a mapX and mapY and a width and height along with a mapoint which makes finding out where the tiles are and if they are solid hard and i was wondering how your progress is with this.

Hope you can help and thanks for all your work so far

mike  on June 13th, 2009

Hi A Person

This is something I am putting into Tutorial 10 now. It can be hard to work this stuff through so I’m adding it to the next tutorial which will be out ASAP.

Hopefully that will be in time to help you.

Mike

MarsMan  on July 8th, 2009

Mike- So many of us would dearly love to see an openAL tutorial on the creation of a musical instrument (like an electric guitar (using audio samples) with pitch bend capability.

Your tutorials ROCK my friend!