javascript - 如何在 webgl 中获得像素化效果？

我想在 webgl 中模拟像 atari 或 commodore 这样的旧电脑低分辨率的效果有没有办法绘制图像然后一些如何使像素更大？

我是 webgl 的新手，所以我应该如何开始做这个效果？

我发现 this 有马赛克效果，但它使用了three.js，我想在没有框架的情况下做到这一点。

最佳答案

有很多方法可以做到。最简单的方法是通过将帧缓冲区附加到低分辨率纹理，然后将该纹理渲染到 Canvas ，并将纹理过滤设置为 NEAREST 。

这是一个示例。它使用的是 TWGL，它不是一个框架，只是一个使 WebGL 不那么冗长的助手。如果您想将其翻译为详细的原始 webgl，请参阅评论(和 docs )。

如果您不熟悉 webgl I'd suggest starting here

const vs = `
attribute vec4 position;
uniform mat4 u_matrix;

void main() {
   gl_Position = u_matrix * position;
}
`;
const fs = `
void main() {
  gl_FragColor = vec4(0, 0, 0, 1); // black
}
`;

const vs2 = `
attribute vec4 position;
attribute vec2 texcoord;

uniform mat4 u_matrix;

varying vec2 v_texcoord;

void main() {
   gl_Position = u_matrix * position;
   v_texcoord = texcoord;
}
`;
const fs2 = `
precision mediump float;
varying vec2 v_texcoord;
uniform sampler2D u_texture;
void main() {
  gl_FragColor = texture2D(u_texture, v_texcoord);
}
`;

"use strict";
const m4 = twgl.m4;
const gl = document.querySelector("canvas").getContext("webgl");
// compiles shaders, links program, looks up locations
const cubeProgramInfo = twgl.createProgramInfo(gl, [vs, fs]);
const texProgramInfo = twgl.createProgramInfo(gl, [vs2, fs2]);

const cubeArrays = {
  position: [
    1, 1, -1, 1, 1, 1, 1, -1, 1, 1, -1, -1, -1, 1, 1, -1, 1, -1, -1, -1, -1, -1, -1, 1, -1, 1, 1, 1, 1, 1, 1, 1, -1, -1, 1, -1, -1, -1, -1, 1, -1, -1, 1, -1, 1, -1, -1, 1, 1, 1, 1, -1, 1, 1, -1, -1, 1, 1, -1, 1, -1, 1, -1, 1, 1, -1, 1, -1, -1, -1, -1, -1],
  indices:  [
    0, 1, 1, 2, 2, 3, 3, 0,
    4, 5, 5, 6, 6, 7, 7, 4,
    8, 9, 9, 10, 10, 11, 11, 8,
    12, 13, 13, 14, 14, 15, 15, 12,
  ],
};
const quadArrays = {
  position: {
    numComponents: 2,
    data: [
      0, 0,
      1, 0,
      0, 1,
      0, 1,
      1, 0,
      1, 1,
    ],
  },
  texcoord: [
    0, 0,
    1, 0,
    0, 1,
    0, 1,
    1, 0,
    1, 1,
  ],
};
// calls gl.createBuffer, gl.bindBuffer, gl.bufferData for each array
const cubeBufferInfo = twgl.createBufferInfoFromArrays(gl, cubeArrays);
const quadBufferInfo = twgl.createBufferInfoFromArrays(gl, quadArrays);

const fbWidth = 32;
const fbHeight = 32;
// make a 32x32 pixel texture
const cubeTexture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, cubeTexture);
gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGBA, fbWidth, fbHeight, 0,
              gl.RGBA, gl.UNSIGNED_BYTE, null);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_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);

// create a depth renderbuffer
const depthBuffer = gl.createRenderbuffer();
gl.bindRenderbuffer(gl.RENDERBUFFER, depthBuffer);
gl.renderbufferStorage(gl.RENDERBUFFER, gl.DEPTH_STENCIL, fbWidth, fbHeight);

// create a framebuffer
const fb = gl.createFramebuffer();
gl.bindFramebuffer(gl.FRAMEBUFFER, fb);

// attach the texture and depth buffer to the framebuffer
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, cubeTexture, 0);
gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.DEPTH_STENCIL_ATTACHMENT, gl.RENDERBUFFER, depthBuffer);

function render(time) {
  time *= 0.001;
  twgl.resizeCanvasToDisplaySize(gl.canvas);

  // draw cube

  // this makes WebGL render to the texture and depthBuffer
  // all draw calls will render there instead of the canvas
  // until we bind something else.
  gl.bindFramebuffer(gl.FRAMEBUFFER, fb);
  gl.viewport(0, 0, fbWidth, fbHeight);
  {
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    const fov = 30 * Math.PI / 180;
    const aspect = fbWidth / fbHeight;
    const zNear = 0.5;
    const zFar = 40;
    const projection = m4.perspective(fov, aspect, zNear, zFar);
    const eye = [1, 4, -7];
    const target = [0, 0, 0];
    const up = [0, 1, 0];

    const camera = m4.lookAt(eye, target, up);
    const view = m4.inverse(camera);
    const viewProjection = m4.multiply(projection, view);
    const world = m4.rotationY(time);

    gl.useProgram(cubeProgramInfo.program);

    // calls gl.bindBuffer, gl.enableVertexAttribArray, gl.vertexAttribPointer
    twgl.setBuffersAndAttributes(gl, cubeProgramInfo, cubeBufferInfo);
    // calls gl.uniformXXX
    twgl.setUniforms(cubeProgramInfo, {
      u_matrix: m4.multiply(viewProjection, world),
    });
    // calls gl.drawArrays or gl.drawElements
    twgl.drawBufferInfo(gl, cubeBufferInfo, gl.LINES);
  }

  // this make WebGL render to the canvas
  gl.bindFramebuffer(gl.FRAMEBUFFER, null);
  gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
  {
     const displayWidth = gl.canvas.clientWidth;
     const displayHeight = gl.canvas.clientHeight;
     const drawHeight = displayHeight;
     const drawWidth = fbWidth * drawHeight / fbHeight;
     const m = m4.ortho(0, gl.canvas.clientWidth, 0, gl.canvas.clientHeight, -1, 1);
     m4.translate(m, [
       (displayWidth - drawWidth) / 2,
       (displayHeight - drawHeight) / 2,
       0], m);
     m4.scale(m, [drawWidth, drawHeight, 1], m);

    gl.useProgram(texProgramInfo.program);
    // calls gl.bindBuffer, gl.enableVertexAttribArray, gl.vertexAttribPointer
    twgl.setBuffersAndAttributes(gl, texProgramInfo, quadBufferInfo);
    // calls gl.uniformXXX, gl.activeTexture, gl.bindTexture
    twgl.setUniforms(texProgramInfo, {
      u_matrix: m,
      u_texture: cubeTexture,
    });
    // calls gl.drawArrays or gl.drawElements
    twgl.drawBufferInfo(gl, quadBufferInfo);
  }

  requestAnimationFrame(render);
}
requestAnimationFrame(render);

body { margin: 0; }
canvas { width: 100vw; height: 100vh; display: block; }

<script src="https://twgljs.org/dist/3.x/twgl-full.min.js"></script>
<canvas></canvas>

渲染到纹理(如上)但分辨率更高的纹理也很常见，然后使用着色器、mips 和/或线性过滤对其进行过滤。优点是你会得到更多的抗锯齿

const vs = `
attribute vec4 position;
uniform mat4 u_matrix;

void main() {
   gl_Position = u_matrix * position;
}
`;
const fs = `
void main() {
  gl_FragColor = vec4(0, 0, 0, 1); // black
}
`;

const vs2 = `
attribute vec4 position;
attribute vec2 texcoord;

uniform mat4 u_matrix;

varying vec2 v_texcoord;

void main() {
   gl_Position = u_matrix * position;
   v_texcoord = texcoord;
}
`;
const fs2 = `
precision mediump float;
varying vec2 v_texcoord;
uniform sampler2D u_texture;
void main() {
  gl_FragColor = texture2D(u_texture, v_texcoord);
}
`;

"use strict";
const m4 = twgl.m4;
const gl = document.querySelector("canvas").getContext("webgl");
// compiles shaders, links program, looks up locations
const cubeProgramInfo = twgl.createProgramInfo(gl, [vs, fs]);
const texProgramInfo = twgl.createProgramInfo(gl, [vs2, fs2]);

const cubeArrays = {
  position: [
    1, 1, -1, 1, 1, 1, 1, -1, 1, 1, -1, -1, -1, 1, 1, -1, 1, -1, -1, -1, -1, -1, -1, 1, -1, 1, 1, 1, 1, 1, 1, 1, -1, -1, 1, -1, -1, -1, -1, 1, -1, -1, 1, -1, 1, -1, -1, 1, 1, 1, 1, -1, 1, 1, -1, -1, 1, 1, -1, 1, -1, 1, -1, 1, 1, -1, 1, -1, -1, -1, -1, -1],
  indices:  [
    0, 1, 1, 2, 2, 3, 3, 0,
    4, 5, 5, 6, 6, 7, 7, 4,
    8, 9, 9, 10, 10, 11, 11, 8,
    12, 13, 13, 14, 14, 15, 15, 12,
  ],
};
const quadArrays = {
  position: {
    numComponents: 2,
    data: [
      0, 0,
      1, 0,
      0, 1,
      0, 1,
      1, 0,
      1, 1,
    ],
  },
  texcoord: [
    0, 0,
    1, 0,
    0, 1,
    0, 1,
    1, 0,
    1, 1,
  ],
};
// calls gl.createBuffer, gl.bindBuffer, gl.bufferData for each array
const cubeBufferInfo = twgl.createBufferInfoFromArrays(gl, cubeArrays);
const quadBufferInfo = twgl.createBufferInfoFromArrays(gl, quadArrays);

// using mips only works if we make texture power of 2 (in WebGL1)
// WebGL2 doesn't have that limit
const fbWidth = 128;
const fbHeight = 128;
// calls gl.createTexture, gl.bindTexture, gl.texImage2D, gl.texParameteri
// calls gl.createRenderbuffer, gl.bindRenderbuffer, gl.renderbufferStorage
// calls gl.createFramebuffer, gl.bindFramebuffer, gl.framebufferTexture2D, gl.framebufferRenderbuffer
const fbInfo = twgl.createFramebufferInfo(gl, [
  { format: gl.RGBA, min: gl.LINEAR_MIPMAP_LINEAR, wrap: gl.CLAMP_TO_EDGE, },
  { format: gl.DEPTH_STENCIL, },
], fbWidth, fbHeight);

// extract the created texture
const cubeTexture = fbInfo.attachments[0];


const lowResFBWidth = 32;
const lowResFBHeight = 32;
const lowResFBInfo = twgl.createFramebufferInfo(gl, [
  { format: gl.RGBA, mag: gl.NEAREST, wrap: gl.CLAMP_TO_EDGE, },
], lowResFBWidth, lowResFBHeight);

// get the texture what was just created.
const lowResTexture = lowResFBInfo.attachments[0];

function render(time) {
  time *= 0.001;
  twgl.resizeCanvasToDisplaySize(gl.canvas);

  // draw cube to the texture

  // calls gl.bindFramebuffer, gl.viewport
  twgl.bindFramebufferInfo(gl, fbInfo);
  {
    gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

    const fov = 30 * Math.PI / 180;
    const aspect = fbWidth / fbHeight;
    const zNear = 0.5;
    const zFar = 40;
    const projection = m4.perspective(fov, aspect, zNear, zFar);
    const eye = [1, 4, -7];
    const target = [0, 0, 0];
    const up = [0, 1, 0];

    const camera = m4.lookAt(eye, target, up);
    const view = m4.inverse(camera);
    const viewProjection = m4.multiply(projection, view);
    const world = m4.rotationY(time);

    gl.useProgram(cubeProgramInfo.program);

    // calls gl.bindBuffer, gl.enableVertexAttribArray, gl.vertexAttribPointer
    twgl.setBuffersAndAttributes(gl, cubeProgramInfo, cubeBufferInfo);
    // calls gl.uniformXXX
    twgl.setUniforms(cubeProgramInfo, {
      u_matrix: m4.multiply(viewProjection, world),
    });
    // calls gl.drawArrays or gl.drawElements
    twgl.drawBufferInfo(gl, cubeBufferInfo, gl.LINES);
  }

  // first generate mips
  gl.bindTexture(gl.TEXTURE_2D, cubeTexture);
  gl.generateMipmap(gl.TEXTURE_2D);

  // draw the texture to the lowResTexture.

  // calls gl.bindFramebuffer, gl.viewport
  twgl.bindFramebufferInfo(gl, lowResFBInfo);
  drawTexture(gl, cubeTexture, fbWidth, fbHeight, lowResFBWidth, lowResFBHeight);

  // draw the low-res texture to the canvas

  // calls gl.bindFramebuffer, gl.viewport
  twgl.bindFramebufferInfo(gl, null);
  drawTexture(gl, lowResTexture, lowResFBWidth, lowResFBHeight, gl.canvas.clientWidth, gl.canvas.clientHeight);

  requestAnimationFrame(render);
}
requestAnimationFrame(render);

function drawTexture(gl, texture, srcWidth, srcHeight, dstWidth, dstHeight) {
   const drawHeight = dstHeight;
   const drawWidth = srcWidth * drawHeight / srcHeight;
   const m = m4.ortho(0, dstWidth, 0, dstHeight, -1, 1);
   m4.translate(m, [
     (dstWidth - drawWidth) / 2,
     (dstHeight - drawHeight) / 2,
     0], m);
   m4.scale(m, [drawWidth, drawHeight, 1], m);

  gl.useProgram(texProgramInfo.program);
  // calls gl.bindBuffer, gl.enableVertexAttribArray, gl.vertexAttribPointer
  twgl.setBuffersAndAttributes(gl, texProgramInfo, quadBufferInfo);
  // calls gl.uniformXXX, gl.activeTexture, gl.bindTexture
  twgl.setUniforms(texProgramInfo, {
    u_matrix: m,
    u_texture: texture,
  });
  // calls gl.drawArrays or gl.drawElements
  twgl.drawBufferInfo(gl, quadBufferInfo);
}

body { margin: 0; }
canvas { width: 100vw; height: 100vh; display: block; }

<script src="https://twgljs.org/dist/3.x/twgl-full.min.js"></script>
<canvas></canvas>

更新

在 2020 年，您可以做的最简单的事情可能就是将 Canvas 设为您想要的分辨率，例如 32x32 并将其 CSS 大小设置为更大，然后使用 image-rendering: pixelated CSS 设置告诉浏览器在缩放图像时不要平滑它

<canvas
    width="32"
    height="32"
    style="
        width: 128px;
        height: 128px;
        image-rendering: crisp-edges; /* for firefox */
        image-rendering: pixelated;   /* for everything else */
    "></canvas>

const vs = `
attribute vec4 position;
uniform mat4 u_matrix;

void main() {
   gl_Position = u_matrix * position;
}
`;
const fs = `
void main() {
  gl_FragColor = vec4(0, 0, 0, 1); // black
}
`;

const vs2 = `
attribute vec4 position;
attribute vec2 texcoord;

uniform mat4 u_matrix;

varying vec2 v_texcoord;

void main() {
   gl_Position = u_matrix * position;
   v_texcoord = texcoord;
}
`;
const fs2 = `
precision mediump float;
varying vec2 v_texcoord;
uniform sampler2D u_texture;
void main() {
  gl_FragColor = texture2D(u_texture, v_texcoord);
}
`;

"use strict";
const m4 = twgl.m4;
const gl = document.querySelector("canvas").getContext("webgl", {
  antialias: false,
});
// compiles shaders, links program, looks up locations
const cubeProgramInfo = twgl.createProgramInfo(gl, [vs, fs]);
const texProgramInfo = twgl.createProgramInfo(gl, [vs2, fs2]);

const cubeArrays = {
  position: [
    1, 1, -1, 1, 1, 1, 1, -1, 1, 1, -1, -1, -1, 1, 1, -1, 1, -1, -1, -1, -1, -1, -1, 1, -1, 1, 1, 1, 1, 1, 1, 1, -1, -1, 1, -1, -1, -1, -1, 1, -1, -1, 1, -1, 1, -1, -1, 1, 1, 1, 1, -1, 1, 1, -1, -1, 1, 1, -1, 1, -1, 1, -1, 1, 1, -1, 1, -1, -1, -1, -1, -1],
  indices:  [
    0, 1, 1, 2, 2, 3, 3, 0,
    4, 5, 5, 6, 6, 7, 7, 4,
    8, 9, 9, 10, 10, 11, 11, 8,
    12, 13, 13, 14, 14, 15, 15, 12,
  ],
};
const quadArrays = {
  position: {
    numComponents: 2,
    data: [
      0, 0,
      1, 0,
      0, 1,
      0, 1,
      1, 0,
      1, 1,
    ],
  },
};
// calls gl.createBuffer, gl.bindBuffer, gl.bufferData for each array
const cubeBufferInfo = twgl.createBufferInfoFromArrays(gl, cubeArrays);

function render(time) {
  time *= 0.001;

  // draw cube
  gl.viewport(0, 0, gl.canvas.width, gl.canvas.height);
  {
    const fov = 30 * Math.PI / 180;
    const aspect = gl.canvas.clientWidth / gl.canvas.clientHeight;
    const zNear = 0.5;
    const zFar = 40;
    const projection = m4.perspective(fov, aspect, zNear, zFar);
    const eye = [1, 4, -7];
    const target = [0, 0, 0];
    const up = [0, 1, 0];

    const camera = m4.lookAt(eye, target, up);
    const view = m4.inverse(camera);
    const viewProjection = m4.multiply(projection, view);
    const world = m4.rotationY(time);

    gl.useProgram(cubeProgramInfo.program);

    // calls gl.bindBuffer, gl.enableVertexAttribArray, gl.vertexAttribPointer
    twgl.setBuffersAndAttributes(gl, cubeProgramInfo, cubeBufferInfo);
    // calls gl.uniformXXX
    twgl.setUniforms(cubeProgramInfo, {
      u_matrix: m4.multiply(viewProjection, world),
    });
    // calls gl.drawArrays or gl.drawElements
    twgl.drawBufferInfo(gl, cubeBufferInfo, gl.LINES);
  }

  requestAnimationFrame(render);
}
requestAnimationFrame(render);

<script src="https://twgljs.org/dist/3.x/twgl-full.min.js"></script>
<canvas
    width="32"
    height="32"
    style="
        width: 128px;
        height: 128px;
        image-rendering: crisp-edges; /* for firefox */
        image-rendering: pixelated;   /* for everything else */
    "></canvas>

关于javascript - 如何在 webgl 中获得像素化效果？，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/43878959/