在 webGL 中使用 Nurbs Surface (Verb)，索引总是错误的，除非我使用角而不是控制点
Using Nurbs Surface (Verb) in webGL, indices are always wrong unless I use corners instead of controlPoints
我正在尝试使 Verb 的 Nurbs Surface 与 vanilla webGL 一起工作（尽管使用 webgl-utils 有点作弊）。 PIXI.js 也产生相同的结果，角落有效，但控制点无效。
我可以使用角 verb.geom.NurbsSurface.byCorners 但是当我尝试使用 verb.geom.NurbsSurface.byKnotsControlPointsWeights 的控制点时，表面变得混乱，很可能是索引错误！
有一个使用 verb with THREE.js 的示例，但即使我尝试使用示例中使用的相同函数，结果也是相同的。
我已经注释掉了基于角的功能，你可以看到它有效。我控制台记录了 srf 并且从 _data 对象我可以看到 Verb 正在生成这些控制点，但是如果我用 byKnotsControlPointsWeights[=19 尝试相同的点将不起作用=]
除了有效的解决方案之外，我还想了解为什么代码不起作用，以及 THREE.js 中的哪一部分与我的普通代码不同，后者使它可以与三个一起使用，但这里不行。
const flatten = _.flatten;
// const corners = [
// [100, 100], // top left
// [450, 50], // top right
// [650, 650], // bottom right
// [0, 750] // bottom left
// ];
// var srf = verb.geom.NurbsSurface.byCorners(...corners);
const degreeU = 3;
const degreeV = 3;
const knotsU = [0, 0, 0, 0, 1, 1, 1, 1];
const knotsV = [0, 0, 0, 0, 1, 1, 1, 1];
const controlPoints = [
[
[0, 0, 1],
[0, 249, 1],
[0, 500, 1],
[0, 750, 1]
],
[
[249, 0, 1],
[249, 249, 1],
[249, 500, 1],
[249, 750, 1]
],
[
[500, 0, 1],
[500, 249, 1],
[500, 500, 1],
[500, 750, 1]
],
[
[750, 0, 1],
[750, 249, 1],
[750, 500, 1],
[750, 750, 1]
]
];
var srf = verb.geom.NurbsSurface.byKnotsControlPointsWeights(
degreeU,
degreeV,
knotsU,
knotsV,
controlPoints
);
// tesselate the nurface and get the triangles
var tess = srf.tessellate();
console.log(tess);
const vertexSource = `
attribute vec2 a_position;
attribute vec2 a_texCoord;
uniform vec2 u_resolution;
varying vec2 v_texCoord;
void main() {
vec2 zeroToOne = a_position / u_resolution;
vec2 zeroToTwo = zeroToOne * 2.0;
vec2 clipSpace = zeroToTwo - 1.0;
gl_Position = vec4(clipSpace * vec2(1, -1), 0, 1);
v_texCoord = a_texCoord;
}
`;
const fragmentSource = `
precision mediump float;
// our texture
uniform sampler2D u_image;
// the texCoords passed in from the vertex shader.
varying vec2 v_texCoord;
void main() {
gl_FragColor = texture2D(u_image, v_texCoord);
}
`;
function main() {
var image = new Image();
image.crossOrigin = "anonymous";
image.onload = function () {
render(image);
};
image.src = "https://pixijs.io/examples/examples/assets/bg_scene_rotate.jpg";
}
function render(image) {
// Get A WebGL context
/** @type {HTMLCanvasElement} */
var canvas = document.getElementById("c");
var gl = canvas.getContext("webgl");
// setup GLSL program
var program = webglUtils.createProgramFromSources(gl, [
vertexSource,
fragmentSource
]);
// look up where the vertex data needs to go.
var positionLocation = gl.getAttribLocation(program, "a_position");
var texcoordLocation = gl.getAttribLocation(program, "a_texCoord");
// Create a buffer to put three 2d clip space points in
var positionBuffer = gl.createBuffer();
// Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = positionBuffer)
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Set a rectangle the same size as the image.
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array(flatten(tess.points)),
gl.STATIC_DRAW
);
// provide texture coordinates for the rectangle.
var texcoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, texcoordBuffer);
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array(flatten(tess.uvs)),
gl.STATIC_DRAW
);
// Create a texture.
var texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);
// Set the parameters so we can render any size image.
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);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
// Upload the image into the texture.
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);
// lookup uniforms
var resolutionLocation = gl.getUniformLocation(program, "u_resolution");
// resize canvas to display size
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
// Tell WebGL how to convert from clip space to pixels
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
// Clear the canvas
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT);
// Tell it to use our program (pair of shaders)
gl.useProgram(program);
// index buffer
const indexBuffer = gl.createBuffer();
// make this buffer the current 'ELEMENT_ARRAY_BUFFER'
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
// Fill the current element array buffer with data
const indices = new Uint16Array(flatten(tess.faces));
gl.bufferData(
gl.ELEMENT_ARRAY_BUFFER,
new Uint16Array(indices),
gl.STATIC_DRAW
);
// Turn on the position attribute
gl.enableVertexAttribArray(positionLocation);
// Bind the position buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Tell the position attribute how to get data out of positionBuffer (ARRAY_BUFFER)
var size = 2; // 2 components per iteration
var type = gl.FLOAT; // the data is 32bit floats
var normalize = false; // don't normalize the data
var stride = 0; // 0 = move forward size * sizeof(type) each iteration to get the next position
var offset = 0; // start at the beginning of the buffer
gl.vertexAttribPointer(
positionLocation,
size,
type,
normalize,
stride,
offset
);
// Turn on the texcoord attribute
gl.enableVertexAttribArray(texcoordLocation);
// bind the texcoord buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, texcoordBuffer);
gl.vertexAttribPointer(
texcoordLocation,
size,
type,
normalize,
stride,
offset
);
// set the resolution
gl.uniform2f(resolutionLocation, gl.canvas.width, gl.canvas.height);
// Draw the rectangle.
gl.drawElements(gl.TRIANGLES, indices.length, gl.UNSIGNED_SHORT, 0);
}
main();
body { margin: 0; }
<script src="https://webglfundamentals.org/webgl/resources/webgl-utils.js"></script>
<script src="https://unpkg.com/verb-nurbs-web@2.1.3/build/js/verb.js"></script>
<script src="https://unpkg.com/lodash@4.17.20/lodash.js"></script>
<canvas id="c"></canvas>
我不知道它应该是什么样子，但是代码在调用 gl.vertexAttribPointer 时传递了 2 作为位置的大小，但数据有 3 (x, y, z)。将其设置为 3 肯定会得到不同的图像。仍然需要确保将 UV 的大小设置为 2
const flatten = _.flatten;
// const corners = [
// [100, 100], // top left
// [450, 50], // top right
// [650, 650], // bottom right
// [0, 750] // bottom left
// ];
// var srf = verb.geom.NurbsSurface.byCorners(...corners);
const degreeU = 3;
const degreeV = 3;
const knotsU = [0, 0, 0, 0, 1, 1, 1, 1];
const knotsV = [0, 0, 0, 0, 1, 1, 1, 1];
const controlPoints = [
[
[0, 0, 1],
[0, 249, 1],
[0, 500, 1],
[0, 750, 1]
],
[
[249, 0, 1],
[249, 249, 1],
[249, 500, 1],
[249, 750, 1]
],
[
[500, 0, 1],
[500, 249, 1],
[500, 500, 1],
[500, 750, 1]
],
[
[750, 0, 1],
[750, 249, 1],
[750, 500, 1],
[750, 750, 1]
]
];
var srf = verb.geom.NurbsSurface.byKnotsControlPointsWeights(
degreeU,
degreeV,
knotsU,
knotsV,
controlPoints
);
// tesselate the nurface and get the triangles
var tess = srf.tessellate();
console.log(tess);
const vertexSource = `
attribute vec2 a_position;
attribute vec2 a_texCoord;
uniform vec2 u_resolution;
varying vec2 v_texCoord;
void main() {
vec2 zeroToOne = a_position / u_resolution;
vec2 zeroToTwo = zeroToOne * 2.0;
vec2 clipSpace = zeroToTwo - 1.0;
gl_Position = vec4(clipSpace * vec2(1, -1), 0, 1);
v_texCoord = a_texCoord;
}
`;
const fragmentSource = `
precision mediump float;
// our texture
uniform sampler2D u_image;
// the texCoords passed in from the vertex shader.
varying vec2 v_texCoord;
void main() {
gl_FragColor = texture2D(u_image, v_texCoord);
}
`;
function main() {
var image = new Image();
image.crossOrigin = "anonymous";
image.onload = function () {
render(image);
};
image.src = "https://pixijs.io/examples/examples/assets/bg_scene_rotate.jpg";
}
function render(image) {
// Get A WebGL context
/** @type {HTMLCanvasElement} */
var canvas = document.getElementById("c");
var gl = canvas.getContext("webgl");
// setup GLSL program
var program = webglUtils.createProgramFromSources(gl, [
vertexSource,
fragmentSource
]);
// look up where the vertex data needs to go.
var positionLocation = gl.getAttribLocation(program, "a_position");
var texcoordLocation = gl.getAttribLocation(program, "a_texCoord");
// Create a buffer to put three 2d clip space points in
var positionBuffer = gl.createBuffer();
// Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = positionBuffer)
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Set a rectangle the same size as the image.
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array(flatten(tess.points)),
gl.STATIC_DRAW
);
// provide texture coordinates for the rectangle.
var texcoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, texcoordBuffer);
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array(flatten(tess.uvs)),
gl.STATIC_DRAW
);
// Create a texture.
var texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);
// Set the parameters so we can render any size image.
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);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
// Upload the image into the texture.
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);
// lookup uniforms
var resolutionLocation = gl.getUniformLocation(program, "u_resolution");
// resize canvas to display size
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
// Tell WebGL how to convert from clip space to pixels
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
// Clear the canvas
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT);
// Tell it to use our program (pair of shaders)
gl.useProgram(program);
// index buffer
const indexBuffer = gl.createBuffer();
// make this buffer the current 'ELEMENT_ARRAY_BUFFER'
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
// Fill the current element array buffer with data
const indices = new Uint16Array(flatten(tess.faces));
gl.bufferData(
gl.ELEMENT_ARRAY_BUFFER,
new Uint16Array(indices),
gl.STATIC_DRAW
);
// Turn on the position attribute
gl.enableVertexAttribArray(positionLocation);
// Bind the position buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Tell the position attribute how to get data out of positionBuffer (ARRAY_BUFFER)
var size = 3; // 2 components per iteration
var type = gl.FLOAT; // the data is 32bit floats
var normalize = false; // don't normalize the data
var stride = 0; // 0 = move forward size * sizeof(type) each iteration to get the next position
var offset = 0; // start at the beginning of the buffer
gl.vertexAttribPointer(
positionLocation,
size,
type,
normalize,
stride,
offset
);
// Turn on the texcoord attribute
gl.enableVertexAttribArray(texcoordLocation);
// bind the texcoord buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, texcoordBuffer);
gl.vertexAttribPointer(
texcoordLocation,
2, //size,
type,
normalize,
stride,
offset
);
// set the resolution
gl.uniform2f(resolutionLocation, gl.canvas.width, gl.canvas.height);
// Draw the rectangle.
gl.drawElements(gl.TRIANGLES, indices.length, gl.UNSIGNED_SHORT, 0);
}
main();
body { margin: 0; }
<script src="https://webglfundamentals.org/webgl/resources/webgl-utils.js"></script>
<script src="https://unpkg.com/verb-nurbs-web@2.1.3/build/js/verb.js"></script>
<script src="https://unpkg.com/lodash@4.17.20/lodash.js"></script>
<canvas id="c"></canvas>
我正在尝试使 Verb 的 Nurbs Surface 与 vanilla webGL 一起工作（尽管使用 webgl-utils 有点作弊）。 PIXI.js 也产生相同的结果，角落有效，但控制点无效。
我可以使用角 verb.geom.NurbsSurface.byCorners 但是当我尝试使用 verb.geom.NurbsSurface.byKnotsControlPointsWeights 的控制点时，表面变得混乱，很可能是索引错误！
有一个使用 verb with THREE.js 的示例，但即使我尝试使用示例中使用的相同函数，结果也是相同的。
我已经注释掉了基于角的功能，你可以看到它有效。我控制台记录了 srf 并且从 _data 对象我可以看到 Verb 正在生成这些控制点，但是如果我用 byKnotsControlPointsWeights[=19 尝试相同的点将不起作用=]
除了有效的解决方案之外，我还想了解为什么代码不起作用，以及 THREE.js 中的哪一部分与我的普通代码不同，后者使它可以与三个一起使用，但这里不行。
const flatten = _.flatten;
// const corners = [
// [100, 100], // top left
// [450, 50], // top right
// [650, 650], // bottom right
// [0, 750] // bottom left
// ];
// var srf = verb.geom.NurbsSurface.byCorners(...corners);
const degreeU = 3;
const degreeV = 3;
const knotsU = [0, 0, 0, 0, 1, 1, 1, 1];
const knotsV = [0, 0, 0, 0, 1, 1, 1, 1];
const controlPoints = [
[
[0, 0, 1],
[0, 249, 1],
[0, 500, 1],
[0, 750, 1]
],
[
[249, 0, 1],
[249, 249, 1],
[249, 500, 1],
[249, 750, 1]
],
[
[500, 0, 1],
[500, 249, 1],
[500, 500, 1],
[500, 750, 1]
],
[
[750, 0, 1],
[750, 249, 1],
[750, 500, 1],
[750, 750, 1]
]
];
var srf = verb.geom.NurbsSurface.byKnotsControlPointsWeights(
degreeU,
degreeV,
knotsU,
knotsV,
controlPoints
);
// tesselate the nurface and get the triangles
var tess = srf.tessellate();
console.log(tess);
const vertexSource = `
attribute vec2 a_position;
attribute vec2 a_texCoord;
uniform vec2 u_resolution;
varying vec2 v_texCoord;
void main() {
vec2 zeroToOne = a_position / u_resolution;
vec2 zeroToTwo = zeroToOne * 2.0;
vec2 clipSpace = zeroToTwo - 1.0;
gl_Position = vec4(clipSpace * vec2(1, -1), 0, 1);
v_texCoord = a_texCoord;
}
`;
const fragmentSource = `
precision mediump float;
// our texture
uniform sampler2D u_image;
// the texCoords passed in from the vertex shader.
varying vec2 v_texCoord;
void main() {
gl_FragColor = texture2D(u_image, v_texCoord);
}
`;
function main() {
var image = new Image();
image.crossOrigin = "anonymous";
image.onload = function () {
render(image);
};
image.src = "https://pixijs.io/examples/examples/assets/bg_scene_rotate.jpg";
}
function render(image) {
// Get A WebGL context
/** @type {HTMLCanvasElement} */
var canvas = document.getElementById("c");
var gl = canvas.getContext("webgl");
// setup GLSL program
var program = webglUtils.createProgramFromSources(gl, [
vertexSource,
fragmentSource
]);
// look up where the vertex data needs to go.
var positionLocation = gl.getAttribLocation(program, "a_position");
var texcoordLocation = gl.getAttribLocation(program, "a_texCoord");
// Create a buffer to put three 2d clip space points in
var positionBuffer = gl.createBuffer();
// Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = positionBuffer)
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Set a rectangle the same size as the image.
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array(flatten(tess.points)),
gl.STATIC_DRAW
);
// provide texture coordinates for the rectangle.
var texcoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, texcoordBuffer);
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array(flatten(tess.uvs)),
gl.STATIC_DRAW
);
// Create a texture.
var texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);
// Set the parameters so we can render any size image.
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);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
// Upload the image into the texture.
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);
// lookup uniforms
var resolutionLocation = gl.getUniformLocation(program, "u_resolution");
// resize canvas to display size
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
// Tell WebGL how to convert from clip space to pixels
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
// Clear the canvas
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT);
// Tell it to use our program (pair of shaders)
gl.useProgram(program);
// index buffer
const indexBuffer = gl.createBuffer();
// make this buffer the current 'ELEMENT_ARRAY_BUFFER'
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
// Fill the current element array buffer with data
const indices = new Uint16Array(flatten(tess.faces));
gl.bufferData(
gl.ELEMENT_ARRAY_BUFFER,
new Uint16Array(indices),
gl.STATIC_DRAW
);
// Turn on the position attribute
gl.enableVertexAttribArray(positionLocation);
// Bind the position buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Tell the position attribute how to get data out of positionBuffer (ARRAY_BUFFER)
var size = 2; // 2 components per iteration
var type = gl.FLOAT; // the data is 32bit floats
var normalize = false; // don't normalize the data
var stride = 0; // 0 = move forward size * sizeof(type) each iteration to get the next position
var offset = 0; // start at the beginning of the buffer
gl.vertexAttribPointer(
positionLocation,
size,
type,
normalize,
stride,
offset
);
// Turn on the texcoord attribute
gl.enableVertexAttribArray(texcoordLocation);
// bind the texcoord buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, texcoordBuffer);
gl.vertexAttribPointer(
texcoordLocation,
size,
type,
normalize,
stride,
offset
);
// set the resolution
gl.uniform2f(resolutionLocation, gl.canvas.width, gl.canvas.height);
// Draw the rectangle.
gl.drawElements(gl.TRIANGLES, indices.length, gl.UNSIGNED_SHORT, 0);
}
main();
body { margin: 0; }
<script src="https://webglfundamentals.org/webgl/resources/webgl-utils.js"></script>
<script src="https://unpkg.com/verb-nurbs-web@2.1.3/build/js/verb.js"></script>
<script src="https://unpkg.com/lodash@4.17.20/lodash.js"></script>
<canvas id="c"></canvas>
我不知道它应该是什么样子，但是代码在调用 gl.vertexAttribPointer 时传递了 2 作为位置的大小，但数据有 3 (x, y, z)。将其设置为 3 肯定会得到不同的图像。仍然需要确保将 UV 的大小设置为 2
const flatten = _.flatten;
// const corners = [
// [100, 100], // top left
// [450, 50], // top right
// [650, 650], // bottom right
// [0, 750] // bottom left
// ];
// var srf = verb.geom.NurbsSurface.byCorners(...corners);
const degreeU = 3;
const degreeV = 3;
const knotsU = [0, 0, 0, 0, 1, 1, 1, 1];
const knotsV = [0, 0, 0, 0, 1, 1, 1, 1];
const controlPoints = [
[
[0, 0, 1],
[0, 249, 1],
[0, 500, 1],
[0, 750, 1]
],
[
[249, 0, 1],
[249, 249, 1],
[249, 500, 1],
[249, 750, 1]
],
[
[500, 0, 1],
[500, 249, 1],
[500, 500, 1],
[500, 750, 1]
],
[
[750, 0, 1],
[750, 249, 1],
[750, 500, 1],
[750, 750, 1]
]
];
var srf = verb.geom.NurbsSurface.byKnotsControlPointsWeights(
degreeU,
degreeV,
knotsU,
knotsV,
controlPoints
);
// tesselate the nurface and get the triangles
var tess = srf.tessellate();
console.log(tess);
const vertexSource = `
attribute vec2 a_position;
attribute vec2 a_texCoord;
uniform vec2 u_resolution;
varying vec2 v_texCoord;
void main() {
vec2 zeroToOne = a_position / u_resolution;
vec2 zeroToTwo = zeroToOne * 2.0;
vec2 clipSpace = zeroToTwo - 1.0;
gl_Position = vec4(clipSpace * vec2(1, -1), 0, 1);
v_texCoord = a_texCoord;
}
`;
const fragmentSource = `
precision mediump float;
// our texture
uniform sampler2D u_image;
// the texCoords passed in from the vertex shader.
varying vec2 v_texCoord;
void main() {
gl_FragColor = texture2D(u_image, v_texCoord);
}
`;
function main() {
var image = new Image();
image.crossOrigin = "anonymous";
image.onload = function () {
render(image);
};
image.src = "https://pixijs.io/examples/examples/assets/bg_scene_rotate.jpg";
}
function render(image) {
// Get A WebGL context
/** @type {HTMLCanvasElement} */
var canvas = document.getElementById("c");
var gl = canvas.getContext("webgl");
// setup GLSL program
var program = webglUtils.createProgramFromSources(gl, [
vertexSource,
fragmentSource
]);
// look up where the vertex data needs to go.
var positionLocation = gl.getAttribLocation(program, "a_position");
var texcoordLocation = gl.getAttribLocation(program, "a_texCoord");
// Create a buffer to put three 2d clip space points in
var positionBuffer = gl.createBuffer();
// Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = positionBuffer)
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Set a rectangle the same size as the image.
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array(flatten(tess.points)),
gl.STATIC_DRAW
);
// provide texture coordinates for the rectangle.
var texcoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, texcoordBuffer);
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array(flatten(tess.uvs)),
gl.STATIC_DRAW
);
// Create a texture.
var texture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, texture);
// Set the parameters so we can render any size image.
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);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
// Upload the image into the texture.
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image);
// lookup uniforms
var resolutionLocation = gl.getUniformLocation(program, "u_resolution");
// resize canvas to display size
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
// Tell WebGL how to convert from clip space to pixels
gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
// Clear the canvas
gl.clearColor(0, 0, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT);
// Tell it to use our program (pair of shaders)
gl.useProgram(program);
// index buffer
const indexBuffer = gl.createBuffer();
// make this buffer the current 'ELEMENT_ARRAY_BUFFER'
gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, indexBuffer);
// Fill the current element array buffer with data
const indices = new Uint16Array(flatten(tess.faces));
gl.bufferData(
gl.ELEMENT_ARRAY_BUFFER,
new Uint16Array(indices),
gl.STATIC_DRAW
);
// Turn on the position attribute
gl.enableVertexAttribArray(positionLocation);
// Bind the position buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Tell the position attribute how to get data out of positionBuffer (ARRAY_BUFFER)
var size = 3; // 2 components per iteration
var type = gl.FLOAT; // the data is 32bit floats
var normalize = false; // don't normalize the data
var stride = 0; // 0 = move forward size * sizeof(type) each iteration to get the next position
var offset = 0; // start at the beginning of the buffer
gl.vertexAttribPointer(
positionLocation,
size,
type,
normalize,
stride,
offset
);
// Turn on the texcoord attribute
gl.enableVertexAttribArray(texcoordLocation);
// bind the texcoord buffer.
gl.bindBuffer(gl.ARRAY_BUFFER, texcoordBuffer);
gl.vertexAttribPointer(
texcoordLocation,
2, //size,
type,
normalize,
stride,
offset
);
// set the resolution
gl.uniform2f(resolutionLocation, gl.canvas.width, gl.canvas.height);
// Draw the rectangle.
gl.drawElements(gl.TRIANGLES, indices.length, gl.UNSIGNED_SHORT, 0);
}
main();
body { margin: 0; }
<script src="https://webglfundamentals.org/webgl/resources/webgl-utils.js"></script>
<script src="https://unpkg.com/verb-nurbs-web@2.1.3/build/js/verb.js"></script>
<script src="https://unpkg.com/lodash@4.17.20/lodash.js"></script>
<canvas id="c"></canvas>