Tile Shader

gistfile1.txt

function setup()
    m=mesh()
    img=readImage("Cargo Bot:Starry Background")
    m.texture=img
    local v,t={},{}
    meshWidth,meshDepth=4000,15000 --huge mesh
    imgScale=0.5 --use the image at this fraction of its normal size, ie reduce it
    --now calculate how many times the image is used along the x and z axes
    --use these as the maximum texture settings
    --the shader will just use the fractional part of the texture mapping
    --(the shader only requires one line to change, to do this)
    local tilesWide,tilesDeep=meshWidth/img.width/imgScale,meshDepth/img.height/imgScale
    local x1,x2,y,z1,z2=-meshWidth/2,meshWidth/2,0,0,-meshDepth
    local tx1,tx2,tz1,tz2=0,tilesWide,0,tilesDeep
    v[1]=vec3(x1,y,z1) t[1]=vec2(tx1,tz1)
    v[2]=vec3(x2,y,z1) t[2]=vec2(tx2,tz1)
    v[3]=vec3(x2,y,z2) t[3]=vec2(tx2,tz2)
    v[4]=vec3(x1,y,z2) t[4]=vec2(tx1,tz2)
    v[5]=vec3(x1,y,z1) t[5]=vec2(tx1,tz1)
    v[6]=vec3(x2,y,z2) t[6]=vec2(tx2,tz2)
    m.vertices=v
    m.texCoords=t
    m.shader=shader(TileShader.vertexShader,TileShader.fragmentShader)
    m:setColors(color(255))
    print("Tile a giant area seamlessly with one image")
end

function draw()
    background(220)
    perspective()
    camera(0,1000,100,0,0,-meshDepth)
    m:draw()
end

TileShader = {
vertexShader = [[
//
// A basic vertex shader
//

//This is the current model * view * projection matrix
// Codea sets it automatically
uniform mat4 modelViewProjection;

//This is the current mesh vertex position, color and tex coord
// Set automatically
attribute vec4 position;
attribute vec4 color;
attribute vec2 texCoord;

//This is an output variable that will be passed to the fragment shader
varying lowp vec4 vColor;
varying highp vec2 vTexCoord;

uniform float flip;   //$$$$

void main()
{
    //Pass the mesh color to the fragment shader
    vColor = color;
    vTexCoord = texCoord;

    //Multiply the vertex position by our combined transform
    gl_Position = modelViewProjection * position;
}

]],
fragmentShader = [[
//
// A basic fragment shader
//

//Default precision qualifier
precision highp float;

//This represents the current texture on the mesh
uniform lowp sampler2D texture;

//The interpolated vertex color for this fragment
varying lowp vec4 vColor;

//The interpolated texture coordinate for this fragment
varying highp vec2 vTexCoord;

void main()
{
    lowp vec4 col = texture2D( texture, vec2(mod(vTexCoord.x,1.0), mod(vTexCoord.y,1.0)));
    gl_FragColor = col;
}

]]}