How to render an isometric tile-based world in Python?

Question

I'm having a bit of trouble rendering an isometric 2D tile-based world using Python and Pygame with the following code:

'''
Map Rendering Demo
rendermap.py
By James Walker (trading as Ilmiont Software).
Copyright (C)Ilmiont Software 2013. All rights reserved.

This is a simple program demonstrating rendering a 2D map in Python with Pygame from a list of map data.
Support for isometric or flat view is included.
'''

import pygame
from pygame.locals import *

pygame.init()

DISPLAYSURF = pygame.display.set_mode((640, 480), DOUBLEBUF)    #set the display mode, window title and FPS clock
pygame.display.set_caption('Map Rendering Demo')
FPSCLOCK = pygame.time.Clock()

map_data = [
[1, 1, 1, 1, 1],
[1, 0, 0, 0, 1],
[1, 0, 0, 0, 1],
[1, 0, 0, 0, 1],
[1, 0, 0, 0, 1],
[1, 1, 1, 1, 1]
]               #the data for the map expressed as [row[tile]].

wall = pygame.image.load('wall.png').convert()  #load images
grass = pygame.image.load('grass.png').convert()

tileWidth = 64  #holds the tile width and height
tileHeight = 64

currentRow = 0  #holds the current map row we are working on (y)
currentTile = 0 #holds the current tile we are working on (x)

for row in map_data:    #for every row of the map...
    for tile in row:
        tileImage = wall

        cartx = currentTile * 64    #x is the index of the currentTile * the tile width
        print(cartx)
        carty = currentRow * 64     #y is the index of the currentRow * the tile height
        print(carty)
        x = cartx - carty
        print(x)
        y = (cartx + carty) / 2
        print(y)
        print('\n\n')
        currentTile += 1    #increase the currentTile holder so we know that we are starting rendering a new tile in a moment

        DISPLAYSURF.blit(tileImage, (x, y)) #display the actual tile
    currentTile = 0 #reset the current working tile to 0 (we're starting a new row remember so we need to render the first tile of that row at index 0)
    currentRow += 1 #increment the current working row so we know we're starting a new row (used for calculating the y coord for the tile)

while True:
    for event in pygame.event.get():
        if event.type == QUIT:
            pygame.quit()
            sys.exit()
        if event.type == KEYUP:
            if event.key == K_ESCAPE:
                pygame.quit()
                sys.exit()

    pygame.display.flip()
    FPSCLOCK.tick(30)

The tile size used is 64x64; the above code when run generates the following output: The tiles all have transparent edges and only the 'wall' tile is featured in this example but obviously something is going wrong as the tiles are all too far apart.

I have tried reading some tutorials online but I can't seem to find one actually written in Python so please advise me as to where I am going wrong.

Thanks in advance, Ilmiont

Answer 1

Try this:

  print(carty)
  x = (cartx - carty) / 2
  print(x)
  y = (cartx + carty)/4*3

And, after test, modify convert() to convert_alpha(), because optimisation kill alpha on convert()

I also modify y ( /4*3 ), to take in account your image. It's work for me.

Answer 2

You can get rid of the black triangles by setting the colorkey to black, I copied your example and was able to fix it by changing:

for row in map_data:    #for every row of the map...
for tile in row:
    tileImage = wall

to

for row in map:
  for tile in row:
    tileImage = wall
    tileImage.set_colorkey((0,0,0))

Found from: https://www.pygame.org/docs/ref/surface.html#pygame.Surface.set_colorkey

There is probably a better way to set the colorkey for all, but I tried this and it seems to work. I see the comment about about alpha, I'm sure that works better too.

In regards to positioning, You would just need to start rendering from the middle of the screen. I was able to do this with your code by simple changing:

x = cartx - carty
print(x)
y = (cartx + carty) / 2

to

x = 320 + ((cartx - carty) / 2)
y = ((cartx+carty) / 4 * 3)

I hope this helps any newcomers to this thread!