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<!-- Ported from the OpenGL Samples Pack https://github.com/g-truc/ogl-samples/blob/master/tests/gl-320-texture-offset.cpp -->

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<title>WebGL 2 Samples - texture_offset</title>

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<div id="info">WebGL 2 Samples - texture_offset</div>

<p id="description">

This sample demonstrates the use of textureOffset(). <br>

LEFT: With offset / RIGHT: Without offset

</p>

<!-- WebGL 2 shaders -->

<script id="vs" type="x-shader/x-vertex">

#version 300 es

#define POSITION_LOCATION 0

#define TEXCOORD_LOCATION 4

precision highp float;

precision highp int;

uniform mat4 MVP;

layout(location = POSITION_LOCATION) in vec2 position;

layout(location = TEXCOORD_LOCATION) in vec2 texcoord;

out vec2 v_st;

void main()

{

v_st = texcoord;

gl_Position = MVP * vec4(position, 0.0, 1.0);

}

</script>

<script id="fs-offset-bicubic" type="x-shader/x-fragment">

#version 300 es

precision highp float;

precision highp int;

uniform sampler2D diffuse;

uniform ivec2 offset;

in vec2 v_st;

out vec4 color;

vec4 catmullRom(in vec4 A, in vec4 B, in vec4 C, in vec4 D, in float s)

{

mat4 catmullRomMatrix = mat4(

vec4(-1.0, 2.0,-1.0, 0.0),

vec4( 3.0,-5.0, 0.0, 2.0),

vec4(-3.0, 4.0, 1.0, 0.0),

vec4( 1.0,-1.0, 0.0, 0.0));

vec4 expo = vec4(s * s * s, s * s, s, 1.0);

return 0.5 * expo * catmullRomMatrix * mat4(

A[0], B[0], C[0], D[0],

A[1], B[1], C[1], D[1],

A[2], B[2], C[2], D[2],

A[3], B[3], C[3], D[3]);

}

vec4 textureCatmullrom(in sampler2D sampler, in vec2 texcoord, in vec2 offset)

{

vec4 texel00 = textureOffset(sampler, texcoord + offset, ivec2(-1,-1));

vec4 texel10 = textureOffset(sampler, texcoord + offset, ivec2( 0,-1));

vec4 texel20 = textureOffset(sampler, texcoord + offset, ivec2( 1,-1));

vec4 texel30 = textureOffset(sampler, texcoord + offset, ivec2( 2,-1));

vec4 texel01 = textureOffset(sampler, texcoord + offset, ivec2(-1, 0));

vec4 texel11 = textureOffset(sampler, texcoord + offset, ivec2( 0, 0));

vec4 texel21 = textureOffset(sampler, texcoord + offset, ivec2( 1, 0));

vec4 texel31 = textureOffset(sampler, texcoord + offset, ivec2( 2, 0));

vec4 texel02 = textureOffset(sampler, texcoord + offset, ivec2(-1, 1));

vec4 texel12 = textureOffset(sampler, texcoord + offset, ivec2( 0, 1));

vec4 texel22 = textureOffset(sampler, texcoord + offset, ivec2( 1, 1));

vec4 texel32 = textureOffset(sampler, texcoord + offset, ivec2( 2, 1));

vec4 texel03 = textureOffset(sampler, texcoord + offset, ivec2(-1, 2));

vec4 texel13 = textureOffset(sampler, texcoord + offset, ivec2( 0, 2));

vec4 texel23 = textureOffset(sampler, texcoord + offset, ivec2( 1, 2));

vec4 texel33 = textureOffset(sampler, texcoord + offset, ivec2( 2, 2));

vec2 splineCoord = fract(vec2(textureSize(sampler, 0)) * texcoord);

vec4 row0 = catmullRom(texel00, texel10, texel20, texel30, splineCoord.x);

vec4 row1 = catmullRom(texel01, texel11, texel21, texel31, splineCoord.x);

vec4 row2 = catmullRom(texel02, texel12, texel22, texel32, splineCoord.x);

vec4 row3 = catmullRom(texel03, texel13, texel23, texel33, splineCoord.x);

return catmullRom(row0, row1, row2, row3, splineCoord.y);

}

void main()

{

ivec2 textureSize = textureSize(diffuse, 0);

color = textureCatmullrom(diffuse, v_st, vec2(offset) / vec2(textureSize));

}

</script>

<script id="fs-bicubic" type="x-shader/x-fragment">

#version 300 es

precision highp float;

precision highp int;

uniform sampler2D diffuse;

in vec2 v_st;

out vec4 color;

vec4 catmullRom(in vec4 A, in vec4 B, in vec4 C, in vec4 D, in float s)

{

mat4 catmullRomMatrix = mat4(

vec4(-1.0, 2.0,-1.0, 0.0),

vec4( 3.0,-5.0, 0.0, 2.0),

vec4(-3.0, 4.0, 1.0, 0.0),

vec4( 1.0,-1.0, 0.0, 0.0));

vec4 expo = vec4(s * s * s, s * s, s, 1.0);

return 0.5 * expo * catmullRomMatrix * mat4(

A[0], B[0], C[0], D[0],

A[1], B[1], C[1], D[1],

A[2], B[2], C[2], D[2],

A[3], B[3], C[3], D[3]);

}

vec4 textureCatmullrom(in sampler2D sampler, in vec2 st)

{

ivec2 size = textureSize(sampler, 0);

ivec2 texelCoord = ivec2(vec2(size) * st);

vec4 texel00 = texelFetchOffset(sampler, texelCoord, 0, ivec2(-1,-1));

vec4 texel10 = texelFetchOffset(sampler, texelCoord, 0, ivec2( 0,-1));

vec4 texel20 = texelFetchOffset(sampler, texelCoord, 0, ivec2( 1,-1));

vec4 texel30 = texelFetchOffset(sampler, texelCoord, 0, ivec2( 2,-1));

vec4 texel01 = texelFetchOffset(sampler, texelCoord, 0, ivec2(-1, 0));

vec4 texel11 = texelFetchOffset(sampler, texelCoord, 0, ivec2( 0, 0));

vec4 texel21 = texelFetchOffset(sampler, texelCoord, 0, ivec2( 1, 0));

vec4 texel31 = texelFetchOffset(sampler, texelCoord, 0, ivec2( 2, 0));

vec4 texel02 = texelFetchOffset(sampler, texelCoord, 0, ivec2(-1, 1));

vec4 texel12 = texelFetchOffset(sampler, texelCoord, 0, ivec2( 0, 1));

vec4 texel22 = texelFetchOffset(sampler, texelCoord, 0, ivec2( 1, 1));

vec4 texel32 = texelFetchOffset(sampler, texelCoord, 0, ivec2( 2, 1));

vec4 texel03 = texelFetchOffset(sampler, texelCoord, 0, ivec2(-1, 2));

vec4 texel13 = texelFetchOffset(sampler, texelCoord, 0, ivec2( 0, 2));

vec4 texel23 = texelFetchOffset(sampler, texelCoord, 0, ivec2( 1, 2));

vec4 texel33 = texelFetchOffset(sampler, texelCoord, 0, ivec2( 2, 2));

vec2 splineCoord = fract(vec2(size * texelCoord));

vec4 row0 = catmullRom(texel00, texel10, texel20, texel30, splineCoord.x);

vec4 row1 = catmullRom(texel01, texel11, texel21, texel31, splineCoord.x);

vec4 row2 = catmullRom(texel02, texel12, texel22, texel32, splineCoord.x);

vec4 row3 = catmullRom(texel03, texel13, texel23, texel33, splineCoord.x);

return catmullRom(row0, row1, row2, row3, splineCoord.y);

}

void main()

{

color = textureCatmullrom(diffuse, v_st);

}

</script>

<script src="utility.js"></script>

<script>

(function () {

'use strict';

var canvas = document.createElement('canvas');

canvas.width = Math.min(window.innerWidth, window.innerHeight);

canvas.height = canvas.width;

document.body.appendChild(canvas);

var gl = canvas.getContext( 'webgl2', { antialias: false } );

var isWebGL2 = !!gl;

if(!isWebGL2) {

document.getElementById('info').innerHTML = 'WebGL 2 is not available. See <a href="https://www.khronos.org/webgl/wiki/Getting_a_WebGL_Implementation">How to get a WebGL 2 implementation</a>';

return;

}

var Corners = {

LEFT: 0,

RIGHT: 1,

MAX: 2

};

var viewports = new Array(Corners.MAX);

viewports[Corners.LEFT] = {

x: 0,

y: canvas.height / 4,

z: canvas.width / 2,

w: canvas.height / 2

};

viewports[Corners.RIGHT] = {

x: canvas.width / 2,

y: canvas.height / 4,

z: canvas.width / 2,

w: canvas.height / 2

};

// -- Init program

var programBicubic = createProgram(gl, getShaderSource('vs'), getShaderSource('fs-bicubic'));

var mvpLocation = gl.getUniformLocation(programBicubic, 'MVP');

var diffuseLocation = gl.getUniformLocation(programBicubic, 'diffuse');

var programOffsetBicubic = createProgram(gl, getShaderSource('vs'), getShaderSource('fs-offset-bicubic'));

var mvpOffsetLocation = gl.getUniformLocation(programOffsetBicubic, 'MVP');

var diffuseOffsetLocation = gl.getUniformLocation(programOffsetBicubic, 'diffuse');

var offsetUniformLocation = gl.getUniformLocation(programOffsetBicubic, 'offset');

// -- Init buffers: vec2 Position, vec2 Texcoord

var positions = new Float32Array([

-1.0, -1.0,

1.0, -1.0,

1.0, 1.0,

1.0, 1.0,

-1.0, 1.0,

-1.0, -1.0

]);

var vertexPosBuffer = gl.createBuffer();

gl.bindBuffer(gl.ARRAY_BUFFER, vertexPosBuffer);

gl.bufferData(gl.ARRAY_BUFFER, positions, gl.STATIC_DRAW);

gl.bindBuffer(gl.ARRAY_BUFFER, null);

var texCoords = new Float32Array([

0.0, 1.0,

1.0, 1.0,

1.0, 0.0,

1.0, 0.0,

0.0, 0.0,

0.0, 1.0

]);

var vertexTexBuffer = gl.createBuffer();

gl.bindBuffer(gl.ARRAY_BUFFER, vertexTexBuffer);

gl.bufferData(gl.ARRAY_BUFFER, texCoords, gl.STATIC_DRAW);

gl.bindBuffer(gl.ARRAY_BUFFER, null);

// -- Init VertexArray

var vertexArray = gl.createVertexArray();

gl.bindVertexArray(vertexArray);

var vertexPosLocation = 0; // set with GLSL layout qualifier

gl.enableVertexAttribArray(vertexPosLocation);

gl.bindBuffer(gl.ARRAY_BUFFER, vertexPosBuffer);

gl.vertexAttribPointer(vertexPosLocation, 2, gl.FLOAT, false, 0, 0);

gl.bindBuffer(gl.ARRAY_BUFFER, null);

var vertexTexLocation = 4; // set with GLSL layout qualifier

gl.enableVertexAttribArray(vertexTexLocation);

gl.bindBuffer(gl.ARRAY_BUFFER, vertexTexBuffer);

gl.vertexAttribPointer(vertexTexLocation, 2, gl.FLOAT, false, 0, 0);

gl.bindBuffer(gl.ARRAY_BUFFER, null);

gl.bindVertexArray(null);

loadImage('../assets/img/Di-3d.png', function(image) {

// -- Init Texture

var texture = gl.createTexture();

gl.activeTexture(gl.TEXTURE0);

gl.bindTexture(gl.TEXTURE_2D, texture);

gl.pixelStorei(gl.UNPACK_FLIP_Y_WEBGL, false);

gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);

gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);

gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);

gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);

gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);

// -- Render

gl.clearColor(0.0, 0.0, 0.0, 1.0);

gl.clear(gl.COLOR_BUFFER_BIT);

gl.bindVertexArray(vertexArray);

var matrix = new Float32Array([

1.0, 0.0, 0.0, 0.0,

0.0, 1.0, 0.0, 0.0,

0.0, 0.0, 1.0, 0.0,

0.0, 0.0, 0.0, 1.0

]);

// No offset

gl.useProgram(programBicubic);

gl.uniformMatrix4fv(mvpLocation, false, matrix);

gl.uniform1i(diffuseLocation, 0);

gl.viewport(viewports[Corners.RIGHT].x, viewports[Corners.RIGHT].y, viewports[Corners.RIGHT].z, viewports[Corners.RIGHT].w);

gl.drawArrays(gl.TRIANGLES, 0, 6);

// Offset

gl.useProgram(programOffsetBicubic);

gl.uniformMatrix4fv(mvpOffsetLocation, false, matrix);

gl.uniform1i(diffuseOffsetLocation, 0);

var offset = new Int32Array([100, -80]);

gl.uniform2iv(offsetUniformLocation, offset);

gl.viewport(viewports[Corners.LEFT].x, viewports[Corners.LEFT].y, viewports[Corners.LEFT].z, viewports[Corners.LEFT].w);

gl.drawArrays(gl.TRIANGLES, 0, 6);

// Delete WebGL resources

gl.deleteBuffer(vertexPosBuffer);

gl.deleteBuffer(vertexTexBuffer);

gl.deleteTexture(texture);

gl.deleteProgram(programOffsetBicubic);

gl.deleteProgram(programBicubic);

gl.deleteVertexArray(vertexArray);

});

})();

</script>

<div id="highlightedLines" style="display: none">#L72-L90</div>

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