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Bruno Oliveira edited this page Sep 10, 2018 · 16 revisions

textri (0.46)

textri x1 y1 x2 y2 x3 y3 u1 v1 u2 v2 u3 v3 [use_map=false] [colorkey=-1]

Parameters:

  • x1 : the x coordinate of the first triangle corner
  • y1 : the y coordinate of the first triangle corner
  • x2 : the x coordinate of the second triangle corner
  • y2 : the y coordinate of the second triangle corner
  • x3 : the x coordinate of the third triangle corner
  • y3 : the y coordinate of the third triangle corner

UV Coordinates

These can be thought of as the window inside image ram (sprite sheet), 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, v=0.

  • u1 : the U coordinate of the first triangle corner

  • v1 : the V coordinate of the first triangle corner

  • u2 : the U coordinate of the second triangle corner

  • v2 : the V coordinate of the second triangle corner

  • u3 : the U coordinate of the third triangle corner

  • v3 : the V coordinate of the third triangle corner

  • use_map : if false (default), the triangle's texture is read from the image vram (sprite sheet). If true, the texture comes from the map ram.

  • colorkey : this is the color to ignore when drawing, transparent

Description:

It renders a triangle filled with texture from image ram or map ram

Use in 3D graphics

This function does not perform perspective correction, so it is not generally suitable for 3D graphics (except in some constrained scenarios). In particular, if the vertices in the triangle have different 3D depth, you may see some distortion.

Example:

-- title:  triangle demo
-- author: MonstersGoBoom
-- desc:   wiki demo for textri
-- 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 

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

UV show

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