how to draw 2d image over 3d scene in processing
In this tutorial, I'll give you a broad overview of what y'all need to know to create isometric worlds. You'll acquire what the isometric projection is, and how to stand for isometric levels as second arrays. We'll codify relationships between the view and the logic, so that we can easily manipulate objects on screen and handle tile-based collision detection. We'll too wait at depth sorting and character animation.
To help speed your game development, y'all can observe a range of isometric game assets on Envato Market, prepare to employ in your game.
i. The Isometric World
Isometric view is a brandish method used to create an illusion of 3D for an otherwise 2D game - sometimes referred to as pseudo 3D or two.5D. These images (taken from Diablo 2 and Historic period of Empires) illustrate what I mean:
Implementing an isometric view tin can be done in many means, just for the sake of simplicity I'll focus on a tile-based approach, which is the almost efficient and widely used method. I've overlaid each screenshot above with a diamond grid showing how the terrain is divide up into tiles.
two. Tile-Based Games
In the tile-based approach, each visual element is broken downwardly into smaller pieces, called tiles, of a standard size. These tiles will exist arranged to form the game globe according to pre-determined level data - usually a 2nd array.
For case allow united states consider a standard top-downward second view with 2 tiles - a grass tile and a wall tile - every bit shown here:
These tiles are each the aforementioned size equally each other, and are each square, so the tile height and tile width are the same.
For a level with grassland enclosed on all sides by walls, the level data'southward 2nd array will look like this:
[[one,1,1,one,1,1], [1,0,0,0,0,1], [1,0,0,0,0,ane], [1,0,0,0,0,1], [one,0,0,0,0,one], [1,1,i,ane,one,one]]
Hither, 0 denotes a grass tile and one denotes a wall tile. Arranging the tiles co-ordinate to the level information will produce the beneath level image:
We can enhance this by adding corner tiles and carve up vertical and horizontal wall tiles, requiring five additional tiles:
[[3,1,1,one,1,4], [2,0,0,0,0,ii], [2,0,0,0,0,2], [ii,0,0,0,0,2], [2,0,0,0,0,ii], [6,1,1,i,1,5]]
I hope the concept of the tile-based approach is now clear. This is a straightforward 2D grid implementation, which nosotros could code similar and so:
for (i, loop through rows) for (j, loop through columns) x = j * tile width y = i * tile height tileType = levelData[i][j] placetile(tileType, x, y)
Here we assume that tile width and tile height are equal (and the aforementioned for all tiles), and match the tile images' dimensions. So, the tile width and tile pinnacle for this example are both 50px, which makes upward the total level size of 300x300px - that is, half dozen rows and six columns of tiles measuring 50x50px each.
In a normal tile-based approach, we either implement a top-downward view or a side view; for an isometric view we need to implement the isometric projection.
three. Isometric Projection
The best technical explanation of what "isometric projection" ways, as far as I'one thousand aware, is from this article by Clint Bellanger:
Nosotros angle our camera along two axes (swing the camera 45 degrees to ane side, then thirty degrees down). This creates a diamond (rhombus) shaped grid where the grid spaces are twice equally wide as they are tall. This style was popularized past strategy games and action RPGs. If we look at a cube in this view, 3 sides are visible (pinnacle and two facing sides).
Although it sounds a bit complicated, actually implementing this view is straightforward. What we demand to understand is the relation betwixt 2D infinite and the isometric space - that is, the relation between the level data and view; the transformation from pinnacle-downwardly "Cartesian" coordinates to isometric coordinates.
(We are non considering a hexagonal tile based technique, which is another manner of implementing isometric worlds.)
Placing Isometric Tiles
Let me endeavor to simplify the human relationship between level information stored as a 2d assortment and the isometric view - that is, how we transform Cartesian coordinates to isometric coordinates.
We will try to create the isometric view for our wall-enclosed grassland level data:
[[one,one,1,1,1,ane], [1,0,0,0,0,1], [1,0,0,0,0,i], [1,0,0,0,0,ane], [ane,0,0,0,0,1], [1,1,1,1,1,1]]
In this scenario nosotros tin determine a walkable area past checking whether the array element is 0 at that coordinate, thereby indicating grass. The second view implementation of the above level was a straightforward iteration with two loops, placing square tiles offsetting each with the stock-still tile meridian and tile width values.
for (i, loop through rows) for (j, loop through columns) 10 = j * tile width y = i * tile height tileType = levelData[i][j] placetile(tileType, 10, y)
For the isometric view, the code remains the same, but the placeTile() part changes.
For an isometric view we demand to calculate the corresponding isometric coordinates within the loops.
The equations to do this are as follows, where isoX and isoY represent isometric 10- and y-coordinates, and cartX and cartY correspond Cartesian x- and y-coordinates:
//Cartesian to isometric: isoX = cartX - cartY; isoY = (cartX + cartY) / 2;
//Isometric to Cartesian: cartX = (2 * isoY + isoX) / 2; cartY = (2 * isoY - isoX) / ii;
These functions show how you can convert from one system to another:
function isoTo2D(pt:Point):Signal{ var tempPt:Signal = new Point(0, 0); tempPt.x = (ii * pt.y + pt.x) / 2; tempPt.y = (2 * pt.y - pt.x) / 2; return(tempPt); } function twoDToIso(pt:Indicate):Signal{ var tempPt:Point = new Bespeak(0,0); tempPt.x = pt.x - pt.y; tempPt.y = (pt.x + pt.y) / two; return(tempPt); } The pseudocode for the loop then looks similar this:
for(i, loop through rows) for(j, loop through columns) x = j * tile width y = i * tile height tileType = levelData[i][j] placetile(tileType, twoDToIso(new Signal(10, y)))
As an example, let's see how a typical 2d position gets converted to an isometric position:
2D point = [100, 100]; // twoDToIso(2nd bespeak) will be calculated as below isoX = 100 - 100; // = 0 isoY = (100 + 100) / ii; // = 100 Iso point == [0, 100];
Similarly, an input of [0, 0] will result in [0, 0], and [ten, v] will give [5, 7.5].
The in a higher place method enables us to create a directly correlation between the 2d level data and the isometric coordinates. Nosotros can find the tile's coordinates in the level data from its Cartesian coordinates using this part:
function getTileCoordinates(pt:Point, tileHeight:Number):Signal{ var tempPt:Point = new Betoken(0, 0); tempPt.x = Math.flooring(pt.x / tileHeight); tempPt.y = Math.flooring(pt.y / tileHeight); return(tempPt); } (Here, we essentially assume that tile elevation and tile width are equal, equally in most cases.)
Hence, from a pair of screen (isometric) coordinates, we can detect tile coordinates by calling:
getTileCoordinates(isoTo2D(screen bespeak), tile height);
This screen point could be, say, a mouse click position or a option-up position.
Tip: Another method of placement is the Zigzag model, which takes a unlike approach altogether.
Moving in Isometric Coordinates
Movement is very easy: you manipulate your game world information in Cartesian coordinates and just utilize the above functions for updating information technology on the screen. For example, if you want to move a character forward in the positive y-direction, y'all can just increment its y holding and then convert its position to isometric coordinates:
y = y + speed; placetile(twoDToIso(new Point(x, y)))
Depth Sorting
In add-on to normal placement, nosotros will need to have care of depth sorting for drawing the isometric world. This makes sure that items closer to the thespian are fatigued on top of items farther away.
The simplest depth sorting method is simply to use the Cartesian y-coordinate value, as mentioned in this Quick Tip: the farther up the screen the object is, the earlier it should be drawn. This work well as long as nosotros do non have whatever sprites that occupy more a unmarried tile infinite.
The most efficient style of depth sorting for isometric worlds is to break all the tiles into standard single-tile dimensions and non to allow larger images. For example, here is a tile which does non fit into the standard tile size - see how nosotros can split it into multiple tiles which each fit the tile dimensions:
4. Creating the Art
Isometric art can be pixel fine art, but it doesn't have to be. When dealing with isometric pixel art, RhysD's guide tells you almost everything yous need to know. Some theory can be institute on Wikipedia as well.
When creating isometric fine art, the general rules are
- Start with a blank isometric grid and adhere to pixel perfect precision.
- Try to break art into single isometric tile images.
- Try to make sure that each tile is either walkable or not-walkable. Information technology will exist complicated if we need to adapt a single tile that contains both walkable and non-walkable areas.
- Most tiles will demand to seamlessly tile in one or more directions.
- Shadows tin be catchy to implement, unless we use a layered approach where nosotros draw shadows on the ground layer and and then draw the hero (or trees, or other objects) on the peak layer. If the approach you lot use is not multi-layered, brand sure shadows fall to the front so that they won't fall on, say, the hero when he stands behind a tree.
- In example you need to use a tile image larger than the standard isometric tile size, try to use a dimension which is a multiple of the iso tile size. Information technology is better to take a layered arroyo in such cases, where we can split the art into unlike pieces based on its height. For example, a tree can be split into three pieces: the root, the trunk, and the foliage. This makes it easier to sort depths as nosotros tin can depict pieces in corresponding layers which corresponds with their heights.
Isometric tiles that are larger than the single tile dimensions volition create issues with depth sorting. Some of the issues are discussed in these links:
5. Isometric Characters
Implementing characters in isometric view is non complicated every bit it may sound. Character art needs to exist created according to certain standards. Start nosotros will demand to fix how many directions of move are permitted in our game - commonly games volition provide iv-manner move or eight-way move.
For a height-down view, we could create a set of grapheme animations facing in one management, and but rotate them for all the others. For isometric grapheme art, we demand to re-render each animation in each of the permitted directions - and then for 8-way motility we need to create viii animations for each action. For ease of agreement nosotros commonly denote the directions as N, North-West, Westward, South-Due west, Southward, South-East, East, and North-Due east, anti-clockwise, in that society.
Nosotros place characters in the same fashion that we place tiles. The movement of a character is accomplished by calculating the movement in Cartesian coordinates and and so converting to isometric coordinates. Let's assume nosotros are using the keyboard to control the character.
We will set up two variables, dX and dY, based on the directional keys pressed. By default these variables will be 0, and volition be updated every bit per the chart below, where U, D, R and Fifty announce the Upwardly, Down, Correct and Left arrow keys, respectively. A value of 1 under a cardinal represents that key being pressed; 0 implies that the central is not being pressed.
Key Pos U D R L dX dY ================ 0 0 0 0 0 0 1 0 0 0 0 i 0 1 0 0 0 -1 0 0 one 0 1 0 0 0 0 ane -one 0 1 0 ane 0 one 1 1 0 0 1 -ane one 0 1 1 0 1 -i 0 i 0 i -1 -ane
Now, using the values of dX and dY, we can update the Cartesian coordinates as so:
newX = currentX + (dX * speed); newY = currentY + (dY * speed);
So dX and dY represent the alter in the 10- and y-positions of the character, based on the keys pressed.
We can easily summate the new isometric coordinates, as we've already discussed:
Iso = twoDToIso(new Bespeak(newX, newY))
Once nosotros have the new isometric position, we need to move the character to this position. Based on the values we accept for dX and dY, we can determine which direction the character is facing and use the corresponding character art.
Standoff Detection
Collision detection is done by checking whether the tile at the calculated new position is a non-walkable tile. And so, once we observe the new position, we don't immediately move the graphic symbol there, but first bank check to see what tile occupies that space.
tile coordinate = getTileCoordinates(isoTo2D(iso indicate), tile top); if (isWalkable(tile coordinate)) { moveCharacter(); } else { //do nada; } In the function isWalkable(), nosotros check whether the level data array value at the given coordinate is a walkable tile or not. Nosotros must take care to update the direction in which the character is facing - even if he does not motility, as in the case of him hitting a not-walkable tile.
Depth Sorting With Characters
Consider a character and a tree tile in the isometric world.
For properly agreement depth sorting, we must sympathise that whenever the character'southward x- and y-coordinates are less than those of the tree, the tree overlaps the character. Whenever the character's ten- and y-coordinates are greater than that of the tree, the character overlaps the tree.
When they have the same x-coordinate, then nosotros make up one's mind based on the y-coordinate alone: whichever has the higher y-coordinate overlaps the other. When they have aforementioned y-coordinate so we decide based on the x-coordinate lonely: whichever has the higher x-coordinate overlaps the other.
A simplified version of this is to just sequentially draw the levels starting from the farthest tile - that is, tile[0][0] - then describe all the tiles in each row one by 1. If a graphic symbol occupies a tile, nosotros draw the ground tile first and then render the graphic symbol tile. This volition piece of work fine, because the character cannot occupy a wall tile.
Depth sorting must be done every time any tile changes position. For case, we demand to do it whenever characters move. We and so update the displayed scene, after performing the depth sort, to reverberate the depth changes.
6. Have a Go!
Now, put your new knowledge to skilful use by creating a working prototype, with keyboard controls and proper depth sorting and collision detection. Here's my demo:
Click to give the SWF focus, then use the pointer keys. Click hither for the full-sized version.
You may discover this utility class useful (I've written it in AS3, but you lot should exist able to understand it in any other programming language):
parcel com.csharks.juwalbose { import flash.display.Sprite; import flash.geom.Point; public class IsoHelper { /** * convert an isometric signal to 2D * */ public static function isoTo2D(pt:Point):Point{ //gx=(two*isoy+isox)/2; //gy=(2*isoy-isox)/2 var tempPt:Bespeak=new Point(0,0); tempPt.x=(2*pt.y+pt.10)/ii; tempPt.y=(2*pt.y-pt.x)/2; return(tempPt); } /** * convert a 2d betoken to isometric * */ public static function twoDToIso(pt:Signal):Point{ //gx=(isox-isoxy; //gy=(isoy+isox)/two var tempPt:Point=new Point(0,0); tempPt.ten=pt.10-pt.y; tempPt.y=(pt.10+pt.y)/2; return(tempPt); } /** * convert a 2d point to specific tile row/cavalcade * */ public static function getTileCoordinates(pt:Point, tileHeight:Number):Point{ var tempPt:Bespeak=new Betoken(0,0); tempPt.10=Math.floor(pt.x/tileHeight); tempPt.y=Math.floor(pt.y/tileHeight); return(tempPt); } /** * convert specific tile row/column to 2d point * */ public static function get2dFromTileCoordinates(pt:Point, tileHeight:Number):Point{ var tempPt:Signal=new Point(0,0); tempPt.x=pt.x*tileHeight; tempPt.y=pt.y*tileHeight; render(tempPt); } } } If yous get actually stuck, hither'south the total lawmaking from my demo (in Wink and AS3 timeline code form):
// Uses senocular's KeyObject class // http://www.senocular.com/flash/actionscript/?file=ActionScript_3.0/com/senocular/utils/KeyObject.as import flash.display.Sprite; import com.csharks.juwalbose.IsoHelper; import flash.display.MovieClip; import flash.geom.Point; import wink.filters.GlowFilter; import flash.events.Event; import com.senocular.utils.KeyObject; import flash.ui.Keyboard; import flash.display.Bitmap; import flash.display.BitmapData; import wink.geom.Matrix; import wink.geom.Rectangle; var levelData=[[ane,ane,i,1,1,one], [ane,0,0,2,0,1], [one,0,1,0,0,one], [i,0,0,0,0,1], [1,0,0,0,0,1], [one,one,1,1,ane,1]]; var tileWidth:uint = fifty; var borderOffsetY:uint = 70; var borderOffsetX:uint = 275; var facing:String = "south"; var currentFacing:Cord = "due south"; var hero:MovieClip=new herotile(); hero.clip.gotoAndStop(facing); var heroPointer:Sprite; var fundamental:KeyObject = new KeyObject(stage);//Senocular KeyObject Class var heroHalfSize:uint=xx; //the tiles var grassTile:MovieClip=new TileMc(); grassTile.gotoAndStop(1); var wallTile:MovieClip=new TileMc(); wallTile.gotoAndStop(2); //the canvas var bg:Bitmap = new Bitmap(new BitmapData(650,450)); addChild(bg); var rect:Rectangle=bg.bitmapData.rect; //to handle depth var overlayContainer:Sprite=new Sprite(); addChild(overlayContainer); //to handle management movement var dX:Number = 0; var dY:Number = 0; var idle:Boolean = true; var speed:uint = 5; var heroCartPos:Indicate=new Point(); var heroTile:Point=new Point(); //add items to start level, add together game loop part createLevel() { var tileType:uint; for (var i:uint=0; i<levelData.length; i++) { for (var j:uint=0; j<levelData[0].length; j++) { tileType = levelData[i][j]; placeTile(tileType,i,j); if (tileType == ii) { levelData[i][j] = 0; } } } overlayContainer.addChild(heroPointer); overlayContainer.alpha=0.5; overlayContainer.scaleX=overlayContainer.scaleY=0.v; overlayContainer.y=290; overlayContainer.10=ten; depthSort(); addEventListener(Result.ENTER_FRAME,loop); } //place the tile based on coordinates function placeTile(id:uint,i:uint,j:uint) { var pos:Point=new Point(); if (id == two) { id = 0; pos.x = j * tileWidth; pos.y = i * tileWidth; pos = IsoHelper.twoDToIso(pos); hero.10 = borderOffsetX + pos.10; hero.y = borderOffsetY + pos.y; //overlayContainer.addChild(hero); heroCartPos.x = j * tileWidth; heroCartPos.y = i * tileWidth; heroTile.x=j; heroTile.y=i; heroPointer=new herodot(); heroPointer.x=heroCartPos.10; heroPointer.y=heroCartPos.y; } var tile:MovieClip=new cartTile(); tile.gotoAndStop(id+1); tile.ten = j * tileWidth; tile.y = i * tileWidth; overlayContainer.addChild(tile); } //the game loop part loop(due east:Effect) { if (key.isDown(Keyboard.Upwards)) { dY = -ane; } else if (primal.isDown(Keyboard.Downwards)) { dY = 1; } else { dY = 0; } if (central.isDown(Keyboard.RIGHT)) { dX = i; if (dY == 0) { facing = "east"; } else if (dY==one) { facing = "southeast"; dX = dY=0.v; } else { facing = "northeast"; dX=0.5; dY=-0.v; } } else if (fundamental.isDown(Keyboard.LEFT)) { dX = -i; if (dY == 0) { facing = "west"; } else if (dY==i) { facing = "southwest"; dY=0.5; dX=-0.5; } else { facing = "northwest"; dX = dY=-0.v; } } else { dX = 0; if (dY == 0) { //facing="westward"; } else if (dY==1) { facing = "s"; } else { facing = "due north"; } } if (dY == 0 && dX == 0) { hero.prune.gotoAndStop(facing); idle = true; } else if (idle||currentFacing!=facing) { idle = fake; currentFacing = facing; hero.clip.gotoAndPlay(facing); } if (! idle && isWalkable()) { heroCartPos.10 += speed * dX; heroCartPos.y += speed * dY; heroPointer.x=heroCartPos.x; heroPointer.y=heroCartPos.y; var newPos:Point = IsoHelper.twoDToIso(heroCartPos); //standoff bank check hero.x = borderOffsetX + newPos.x; hero.y = borderOffsetY + newPos.y; heroTile=IsoHelper.getTileCoordinates(heroCartPos,tileWidth); depthSort(); //trace(heroTile); } tileTxt.text="Hero is on ten: "+heroTile.ten +" & y: "+heroTile.y; } //check for collision tile function isWalkable():Boolean{ var able:Boolean=true; var newPos:Betoken =new Betoken(); newPos.x=heroCartPos.x + (speed * dX); newPos.y=heroCartPos.y + (speed * dY); switch (facing){ case "n": newPos.y-=heroHalfSize; break; case "s": newPos.y+=heroHalfSize; break; case "east": newPos.x+=heroHalfSize; break; example "west": newPos.x-=heroHalfSize; pause; case "northeast": newPos.y-=heroHalfSize; newPos.x+=heroHalfSize; intermission; instance "southeast": newPos.y+=heroHalfSize; newPos.ten+=heroHalfSize; intermission; case "northwest": newPos.y-=heroHalfSize; newPos.x-=heroHalfSize; break; example "southwest": newPos.y+=heroHalfSize; newPos.10-=heroHalfSize; interruption; } newPos=IsoHelper.getTileCoordinates(newPos,tileWidth); if(levelData[newPos.y][newPos.x]==1){ able=false; }else{ //trace("new",newPos); } return able; } //sort depth & draw to canvas part depthSort() { bg.bitmapData.lock(); bg.bitmapData.fillRect(rect,0xffffff); var tileType:uint; var mat:Matrix=new Matrix(); var pos:Signal=new Point(); for (var i:uint=0; i<levelData.length; i++) { for (var j:uint=0; j<levelData[0].length; j++) { tileType = levelData[i][j]; //placeTile(tileType,i,j); pos.x = j * tileWidth; pos.y = i * tileWidth; pos = IsoHelper.twoDToIso(pos); mat.tx = borderOffsetX + pos.10; mat.ty = borderOffsetY + pos.y; if(tileType==0){ bg.bitmapData.draw(grassTile,mat); }else{ bg.bitmapData.draw(wallTile,mat); } if(heroTile.ten==j&&heroTile.y==i){ mat.tx=hero.10; mat.ty=hero.y; bg.bitmapData.describe(hero,mat); } } } bg.bitmapData.unlock(); //add together graphic symbol rectangle } createLevel(); Registration Points
Requite special consideration to the registration points of the tiles and the hero. (Registration points can be thought of as the origin points for each particular sprite.) These mostly won't fall within the image, but rather will be the top left corner of the sprite's bounding box.
Nosotros volition have to alter our drawing code to fix the registration points correctly, mainly for the hero.
Collision Detection
Another interesting point to note is that we calculate collision detection based on the signal where the hero is.
But the hero has volume, and cannot exist accurately represented by a unmarried bespeak, so we need to represent the hero as a rectangle and check for collisions against each corner of this rectangle so that there are no overlaps with other tiles and hence no depth artifacts.
Shortcuts
In the demo, I simply redraw the scene over again each frame based on the new position of the hero. We detect the tile which the hero occupies and depict the hero on height of the basis tile when the rendering loops reach those tiles.
Simply if we look closer, we will find that there is no need to loop through all the tiles in this instance. The grass tiles and the summit and left wall tiles are always drawn before the hero is drawn, so nosotros don't ever need to redraw them at all. As well, the bottom and correct wall tiles are e'er in front of the hero and hence fatigued later the hero is fatigued.
Essentially, then, we just need to perform depth sorting betwixt the wall inside the agile area and the hero - that is, two tiles. Noticing these kinds of shortcuts will help you save a lot of processing fourth dimension, which tin be crucial for performance.
Conclusion
Past now, yous should accept a bully basis for building isometric games of your own: you can render the world and the objects in it, stand for level data in uncomplicated 2d arrays, convert between Cartesian and isometric coordiates, and deal with concepts like depth sorting and graphic symbol animation. Enjoy creating isometric worlds!
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Source: https://gamedevelopment.tutsplus.com/tutorials/creating-isometric-worlds-a-primer-for-game-developers--gamedev-6511
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