ttri

ttri(x1, y1, x2, y2, x3, y3, u1, v1, u2, v2, u3, v3, [texsrc=0], [chromakey=-1], z1=0, z2=0, z3=0)

Parameters

x1, y1 : the screen coordinates of the first corner
x2, y2 : the screen coordinates of the second corner
x3, y3 : the screen coordinates of the third corner
u1, v1 : the UV coordinates of the first corner
u2, v2 : the UV coordinates of the second corner
u3, v3 : the UV coordinates of the third corner
texsrc : if 0 (default), the triangle's texture is read from SPRITES RAM. If 1, the texture comes from the MAP RAM.
If 2, the texture comes from the screen RAM in the next VBANK (the one following the VBANK on which the ttri() is set to be displayed) (e.g., a ttri() on vbank(0) with the texsrc=2 will use vbank(1) as its texture at the time of its execution and vice versa).
chromakey : index (or array of indexes 0.80) of the color(s) that will be used as transparent
z1, z2, z3 : depth parameters for perspective correction and depth buffer

A note on UV Coordinates

The letters "U" and "V" denote the axes of the 2D texture because "X", "Y" are already used. These can be thought of as the window inside SPRITES or MAP RAM. Note that the sprite sheet or map in this case is treated as a single large image, with U and V addressing its pixels directly, rather than by sprite ID. So for example the top left corner of sprite #2 would be located at u=16 (horizontal), v=0 (vertical).

Description

This function draws a triangle filled with texture from either SPRITES or MAP RAM or VBANK.

Depth Buffer

A depth buffer is implemented when z1, z2, z3 arguments are set. The depth buffer uses vbank switching vbank(0)/vbank(1) into which you can write/read. It can also be cleared using the cls() function (https://github.com/nesbox/TIC-80/blob/main/src/core/draw.c#L397).

Examples

-- title:  triangle demo
-- author: MonstersGoBoom
-- desc:   wiki demo for ttri
-- script: lua
-- input:  gamepad

usize = 32
vsize = 32
function TIC()
  cls(1)
  if btn(0) then usize=usize-1 end
  if btn(1) then usize=usize+1 end
  if btn(2) then vsize=vsize-1 end
  if btn(3) then vsize=vsize+1 end

-- draw a scaling view into the map ram

  ttri(0,0,
         64,0,
         0,64,
         0,0,
         usize,0,
         0,vsize,
         true,
         14)
  ttri(64,0,
         0,64,
         64,64,
         usize,0,
         0,vsize,
         usize,vsize,
         true,
         14)
end