Game Programming - Episode 35 - Level Render

Key Takeaways

hey what's up guys my name is aern welcome to episode 35 of game programming so last time we took a look at this screen do set offset method that we made here and how that how that actually controlled the offsets of our tiles on our screens now what we're actually going to do today is render those tiles so if I go over here to level we've got these four corner pins that we actually talked about a few episodes back and we actually need to um apply them so in other words if I open if I open my um my game you notice that they're the four corner pins right so in other words what what we sort of want to do is render from this side of the screen to this side of the screen for x and from that from this side of the screen to this uh part of the screen um for y so obviously that's going to be just a full loop so let's talk about this now so four and we'll we'll manage y first four in y equals now before you type zero we're not actually going to be we're not actually going to type zero because that's you know not necessarily going to be zero we're going to type y0 because y0 is the top part of the screen so for y = y0 y is less than the bottom part of the screen y1 Y ++ and we're going to do the same thing for X so for in and remember this is inside whoops that this this x that that I'm about to type right here it is inside the Y um the wide Loop so it's a nested for Loop for in x = x0 x is less than X1 x++ now I'm going to explain this code real quick um if I open up our window we know that y0 is up here y1 is down here right x0 is this left side and X1 is this whoops and X1 is this right side here so what I'm saying here is I'm saying that we want to render from the top part of the screen to the bottom part of the screen so every number in between this very top pixel up here to this very bottom pixel over here and I also want to render every every single um pixel from this this left most pixel to the right most pixel all right that is what that code is doing it's cycling through every number between the top and bottom and the right and left or the left and right technically um okay sweet so what I want to do now is actually you know get the right tile to render so we can do that very simply simply by calling this get tile method and then accessing if I go back into our tile class you'll see that we've got this render method in our tile and if I go into the grass Tile For example you'll see that what that render method actually does is it renders it CLA the screens render tile method and actually renders a tile onto the screen that's what we want to do right we want to render a tile onto the screen so we'll simply call this get tile method by typing get tile now this is important because we want to be able to get the right tile to render um now it's not actually very hard all we do is we Type X comma Y and that's it because we need to input the X position of the tile and the Y position of the tile but remember this is these are those positions all right we're dividing remember we're dividing everything by 16 so we're getting it into tile precision and I talked a bit about pixel pixel precision versus tile Precision a few episodes ago and so what we're doing here is by dividing this x scl value by 16 we're actually you know being like all right every 16 pixels equals one tile so in other words when we actually look up this in this array here um on a specific index you know we're saying that at at these two coordinates what tile is there and then we find out that if in that array the tile at these this x comma y coordinate equals zero then yeah we're returning a grass tile otherwise will just return aoid tile so that is all we need to do because remember these values are getting getting their this y here in this x they're getting their values from these Corner pins and that those Corner pins are intile Precision so that's it that's it's as simple as that you know we've we've managed to get every pixel on the screen into tile Precision so that our program actually knows what tile is where and which tile ends where and starts where so in other words it knows that the first 16 pixel for example is one tile so now that we've called the get tile method which is brilliant what we need to do now is actually render them and rendering them is very simple because you know normally when you're calling a method you just end it like that and that's all fine but remember this method isn't just a void method it actually returns a tile you can see here that it returns a tile and so we can actually use it to access our tile class um like this tile. render class um as if as if it was just you know as if as if it was just tile do whatever so let's get rid of the semicolon and we'll simply type get tile XY which will return us some kind of tile object and then simply do render and now we need to actually fill out these details which are extremely easy as well they're actually all there on the screen for us already so we're going to render them at these positions and that's it that is actually going to render a tile onto the screen um now one thing I want to quickly mention here is why we can do this now you'll notice here that in the tile class which is right over here um we've got this random method and it's not actually doing anything you can see there it just sort of exists there but there's no code inside it and you guys might be like you know why is it there then it doesn't really do anything why is it there because the thing is if we actually you know do this so if we remove it I'm just commenting it out which is the same as removing it really you'll see that we're actually getting error here and you guys might be like but hang on a minute I'm trying to render a grass tile if I go to my grass tile the render method exists but the thing is we're returning a tile we're not returning a grass tile we're returning a grass tile yeah that method will work but we're returning a tile so in other words even if it's returning a grass tile object the actual method needs to be in the tile object because the thing is Java can't just assume that we're going to return a grass tile every time what if we're returning a void tile and what if void tile doesn't actually have a render method because for example I don't know it might not render like it does in this case but if it didn't have a if it didn't have a random method and we returned it it would crash because we just get method not found so Java actually says that all right if you're if you're using classes that extend other classes the actual super class which is in this case tile it has to have a random method it has to have a method it has to have that base method so that you know worst comes to worst I'll just run nothing I'll just run what's in this code if I don't find it in our sub classes so I hope that makes sense um it's not actually uh very easy to understand but you know if you think about it a lot I think you will be able to understand it but um yeah so this line of code over here get tile XY render it's going to get the um the appropriate tile at that particular location and it's going to render it also at this location on the screen and that is it so I hope you enjoyed this episode of game programming guys and I will see you guys next time [Music] goodbye