Complete draft of spider doc and add code for this.

doc/projects/03-house.md → doc/projects/04-spider.md

@@ -56,7 +56,6 @@ at point(15, 9, 0) and draw 7 blocks down using point(1, -7, 1)
 
 	box(OBSIDIAN, point(15, 9, 0), point(1, -7, 1))
 
-//Testme
 ## Step 3 Make a function for drawing legs
 
 * But you need to draw 8 legs, 4 on each side.  This is where we can use something 
@@ -79,13 +78,13 @@ or just press the "tab" key once:
 Now we can "call" this function by simply adding this to the bottom of your
 program.  Your code should now look something like this:
 
+	sphere(DIAMOND_BLOCK, point(0, 10, 0), 8)
+	sphere(DIAMOND_BLOCK, point(0, 10, 7 + 6), 6)
+	
 	def leg():
 		box(OBSIDIAN, point(8, 10, 0), point(8, 1, 1))
 		box(OBSIDIAN, point(15, 9, 0), point(1, -7, 1))
 
-
-	sphere(DIAMOND_BLOCK, point(0, 10, 0), 8)
-	sphere(DIAMOND_BLOCK, point(0, 10, 7 + 6), 6)
 	leg()	
 	
 * Press F5 - your spider should appear with one leg, now we need to make
@@ -101,7 +100,8 @@ add "pos" to all of the positions of the shapes:
 		box(OBSIDIAN, pos+point(7, -1, 0), point(1, -7, 1))
 
 * We can now pass in the position when we call the function to draw a leg
-in any position. This will draw 4 legs on one side of the body, spaced apart by a block.
+in any position. This will draw 4 legs on one side of the body, spaced apart 
+by a block.  Change the "leg()" line to the following:
 
 	leg(point(8, 10, 1))
 	leg(point(8, 10, 3))
@@ -141,5 +141,203 @@ for loop to do this:
 * Press F5 to test again - your legs should now be positioned either side
 of the vertical centre line of the sphere.
 
+## Step 5 Repeat after me.
+
+So now we need to draw some legs the other side of the spider, we need to
+do two things:
+
+* Position the legs on the other side of the body - this means changing one
+of the parameters for our point to a negative value. We can be lazy and use
+the same loop again, bonus! Copy the code which calls the leg function and 
+repeat it underneath the line you copied:
+
+	for i in range(-2, 2):
+		leg(point(8, 10, i * 2 + 1))
+		leg(point(8, 10, i * 2 + 1))
+
+* Right, now change one of the three parameters to a negative value.  See if
+you can work out the correct one to do before you press F5.
+
+* This code will only move the legs to start at the other side of the spider,
+they will disappear inside it if you are correct.  If you get it
+wrong, try again.  The correct code will be shown later.
+
+## Step 6 Flip it.
+
+* The second thing we need to do is turn the legs around so they stick out
+from the spider.  We can use our function to help us again and pass in a
+Boolean (True or False) parameter which says whether to flip them around 
+the other way.
+
+* Because of the way the sphere is drawn, we need to jiggle our maths a little
+to make the legs draw correctly.  The code below shows the function and the
+for loop which calls it - replace your leg drawing code with this:
+
+	def leg(pos, flip):
+		if(flip):
+			box(GOLD_BLOCK, pos+point(-7, 0, 0), point(8, 1, 1))
+			box(OBSIDIAN, pos+point(-7, -1, 0), point(1, -7, 1))
+		else:
+			box(GOLD_BLOCK, pos, point(8, 1, 1))
+			box(OBSIDIAN, pos+point(7, -1, 0), point(1, -7, 1))
+
+	for i in range(-2, 2):
+		leg(point(8, 10, i * 2 + 1), False)
+		leg(point(-8, 10, i * 2 + 1), True)
+
+## Step 7 Eyes.
+
+* Spiders have 8 eyes, so we will try and give our creature some.  We will
+do this programmatically, but remember how the sphere had an odd diameter?
+This means we'll have to be arrange our eyes so they don't look off centre.
+Computers are good at loops so we will use this to make a check pattern.
+
+* We also want the eyes to be at the front of the head, so we need to move
+them from the centre of the spider forward - how far do you think this is?
+
+* The distance is the radius of the body + the diameter of the head.
+
+* First we will write some code to draw 8 blocks in a 3 x 2 check pattern.
+We will make 2 loops to do 3 rows of 5 columns and draw a block every other loop.
+We use a Boolean "flag" like the flip for the legs to decide whether to
+draw a block.  Each time we go through our loop we "toggle" the flag, to be
+the opposite of what it was last time. This means we can do a check pattern
+quite simply.
+
+* Add the following code to the bottom of your file:
+
+	draw = True
+	for x in range(-2, 3):
+		for y in range(-1, 2):
+			if True == draw:
+				box(GOLD_BLOCK, point(x, y + 10, 20), point(1, 1, 1))
+			draw = ~draw
+
+* Press F5 to test and you should see the eyes appear in a check pattern
+in front of the spiders head. We have a gap between the head and eyes because
+we chose "20" for the z- position just to get it working.
+
+* Right, lets put this in a function so we can tell it where to put the
+eyes easily.  Remove the code you just wrote and replace it with the following:
+
+	def eyes(pos):
+		draw = True
+		for x in range(-2, 3):
+			for y in range(-1, 2):
+				if True == draw:
+					box(GOLD_BLOCK, point(pos.x + x, pos.y + y, pos.z), point(1, 1, 1))
+				draw = ~draw
+
+	eyes(point(0, 10, 19))
+
+## Step 8 Tidy up.
+
+* Right we've got a spider like thing on the screen, but what about those colours?
+
+* Lets make a function to draw the spider with a colour for the body and head
+and another colour for the legs and eyes.
+
+* Whilst we are here, let's make it so you can draw the spider in any position on
+the map.
+
+* We need to move our functions round a little, so some copy and paste might be useful.
+Try to move all your "def" functions above your function calls so your code looks
+like this:
+
+	from dbscode_minecraft import *
+
+	bulldoze()
+	
+	def leg(pos, flip):
+		if(flip):
+			box(GOLD_BLOCK, pos+point(-7, 0, 0), point(8, 1, 1))
+			box(OBSIDIAN, pos+point(-7, -1, 0), point(1, -7, 1))
+		else:
+			box(GOLD_BLOCK, pos, point(8, 1, 1))
+			box(OBSIDIAN, pos+point(7, -1, 0), point(1, -7, 1))
+
+	def eyes(pos):
+		draw = True
+		for x in range(-2, 3):
+			for y in range(-1, 2):
+				if True == draw:
+					box(GOLD_BLOCK, point(pos.x + x, pos.y + y, pos.z), point(1, 1, 1))
+				draw = ~draw
+
+	sphere(DIAMOND_BLOCK, point(0, 10, 0), 8)
+	sphere(DIAMOND_BLOCK, point(0, 10, 7 + 6), 6) 
+	for i in range(-2, 2):
+		leg(point(8, 10, i * 2 + 1), False)
+		leg(point(-8, 10, i * 2 + 1), True)
+
+	eyes(point(0, 10, 19))
+	
+* Now create a spider function which draws the 2 spheres, the legs and eyes.
+This needs to take 3 parameters, the colours and the position.
+
+	def spider(body_colour, leg_colour, pos):
+
+* Which code goes inside the function?
+
+* How would you call the function?
+
+* Can you change the sphere functions to use the body colour?
+
+* Can you change the sphere functions to draw the body and head in the position
+you chose?
+
+* Can you add another parameter to the leg and eye functions so you can
+tell it the colour you want?
+
+* Can you reposition the legs with the position of the spider?
+
+* Here is the whole code that should do all this:
+
+	from dbscode_minecraft import *
+
+	bulldoze()
+
+	def leg(pos, flip, colour):
+		if(flip):
+			box(colour, pos+point(-7, 0, 0), point(8, 1, 1))
+			box(colour, pos+point(-7, -1, 0), point(1, -7, 1))
+		else:
+			box(colour, pos, point(8, 1, 1))
+			box(colour, pos+point(7, -1, 0), point(1, -7, 1))
+
+	def eyes(pos, colour):
+		draw = True
+		for x in range(-2, 3):
+			for y in range(-1, 2):
+				if True == draw:
+					box(colour, point(pos.x + x, pos.y + y, pos.z), point(1, 1, 1))
+				draw = ~draw
+
+	def spider(body_colour, leg_colour, pos):
+		sphere(body_colour, pos, 8)
+		sphere(body_colour, pos+point(0, 0, 13), 6) 
+		for i in range(-2, 2):
+			leg(pos+point(8, 0, i * 2 + 1), False, leg_colour)
+			leg(pos+point(-8, 0, i * 2 + 1), True, leg_colour)
+
+		eyes(pos+point(0, 0, 19), leg_colour)
+		
+	spider(OBSIDIAN, GOLD_BLOCK, point(0, 10, 0))
+
+
+## Step 9 Spidercraft
+
+* So you can make a spider, but can you make more of them?  How might you do
+that?
+
+* Could you make 3 spiders in a line with different colours?
+
+* How might you make things a bit more random, could you make each spider
+have a random size?  If you do this, how do you make the head and legs stay in
+proportion to the body?
+
+* What happens if you try to draw 10 spiders?
 
+* Could you invent some new creatures?
 
+* Could you re-use some of the code to draw a snowman?

experiments/spider-doc.py

+from dbscode_minecraft import *
+
+bulldoze()
+
+def leg(pos, flip, colour):
+	if(flip):
+		box(colour, pos+point(-7, 0, 0), point(8, 1, 1))
+		box(colour, pos+point(-7, -1, 0), point(1, -7, 1))
+	else:
+		box(colour, pos, point(8, 1, 1))
+		box(colour, pos+point(7, -1, 0), point(1, -7, 1))
+
+def eyes(pos, colour):
+	draw = True
+	for x in range(-2, 3):
+		for y in range(-1, 2):
+			if True == draw:
+				box(colour, point(pos.x + x, pos.y + y, pos.z), point(1, 1, 1))
+			draw = ~draw
+
+def spider(body_colour, leg_colour, pos):
+	sphere(body_colour, pos, 8)
+	sphere(body_colour, pos+point(0, 0, 13), 6) 
+	for i in range(-2, 2):
+		leg(pos+point(8, 0, i * 2 + 1), False, leg_colour)
+		leg(pos+point(-8, 0, i * 2 + 1), True, leg_colour)
+
+	eyes(pos+point(0, 0, 19), leg_colour)
+	
+spider(OBSIDIAN, GOLD_BLOCK, point(0, 10, 0))