I know webgl can antialias or multisample stuff you render to the screen to avoid hard edges, but when I used a framebuffer it didnt do it anymore and there were a bunch of jagged edges on the screen.
How can I make the framebuffer use multisampling?
This took me a day to figure out, so I thought I should post an example for others to follow. I borrowed the cube animation code below from webgl2fundamentals.org. All I have added to it is the code that does antialiasing on the 3d texture. Make sure the context is initialized with canvas.getContext("webgl2", {antialias: false});
This method won't work with antialiasing on.
To antialias a generated texture you need to initialize a Renderbuffer
object and two Framebuffer
objects, one for storing the drawing, and the other to process the antialiased graphics into afterwards.
// Create and bind the framebuffer
const FRAMEBUFFER =
{
RENDERBUFFER: 0,
COLORBUFFER: 1
};
const fb =
[
gl.createFramebuffer(),
gl.createFramebuffer()
];
const colorRenderbuffer = gl.createRenderbuffer();
gl.bindRenderbuffer(gl.RENDERBUFFER,
colorRenderbuffer);
gl.renderbufferStorageMultisample(gl.RENDERBUFFER,
gl.getParameter(gl.MAX_SAMPLES),
gl.RGBA8,
targetTextureWidth,
targetTextureHeight);
gl.bindFramebuffer(gl.FRAMEBUFFER,
fb[FRAMEBUFFER.RENDERBUFFER]);
gl.framebufferRenderbuffer(gl.FRAMEBUFFER,
gl.COLOR_ATTACHMENT0,
gl.RENDERBUFFER,
colorRenderbuffer);
gl.bindFramebuffer(gl.FRAMEBUFFER,
fb[FRAMEBUFFER.COLORBUFFER]);
gl.framebufferTexture2D(gl.FRAMEBUFFER,
gl.COLOR_ATTACHMENT0,
gl.TEXTURE_2D,
targetTexture, 0);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
Just before drawing what will become your texture, set the Framebuffer
as the first of the two Framebuffer
objects.
// render to our targetTexture by binding the framebuffer
gl.bindFramebuffer(gl.FRAMEBUFFER,
fb[FRAMEBUFFER.RENDERBUFFER]);
Then do the texture drawing, and then do the antialiasing, which will require the second buffer.
// ... drawing code ...
//
// "blit" the cube into the color buffer, which adds antialiasing
gl.bindFramebuffer(gl.READ_FRAMEBUFFER,
fb[FRAMEBUFFER.RENDERBUFFER]);
gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER,
fb[FRAMEBUFFER.COLORBUFFER]);
gl.clearBufferfv(gl.COLOR, 0, [1.0, 1.0, 1.0, 1.0]);
gl.blitFramebuffer(0, 0, targetTextureWidth, targetTextureHeight,
0, 0, targetTextureWidth, targetTextureHeight,
gl.COLOR_BUFFER_BIT, gl.LINEAR);
// render the top layer to the framebuffer as well
gl.bindFramebuffer(gl.FRAMEBUFFER,
fb[FRAMEBUFFER.RENDERBUFFER]);
Once you have finished drawing the top layer into the buffer, use the same antialiasing method from before, this time setting DRAW_FRAMEBUFFER
to null
; this tells it to draw to the actual canvas.
// this time render to the default buffer, which is just canvas
gl.bindFramebuffer(gl.READ_FRAMEBUFFER,
fb[FRAMEBUFFER.RENDERBUFFER]);
gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, null);
gl.clearBufferfv(gl.COLOR, 0, [1.0, 1.0, 1.0, 1.0]);
gl.blitFramebuffer(0, 0, canvas.width, canvas.height,
0, 0, canvas.width, canvas.height,
gl.COLOR_BUFFER_BIT, gl.LINEAR);
Here is the finished product:
"use strict";
var vertexShaderSource = `#version 300 es
// an attribute is an input (in) to a vertex shader.
// It will receive data from a buffer
in vec4 a_position;
in vec2 a_texcoord;
// A matrix to transform the positions by
uniform mat4 u_matrix;
// a varying to pass the texture coordinates to the fragment shader
out vec2 v_texcoord;
// all shaders have a main function
void main() {
// Multiply the position by the matrix.
gl_Position = u_matrix * a_position;
// Pass the texcoord to the fragment shader.
v_texcoord = a_texcoord;
}
`;
var fragmentShaderSource = `#version 300 es
precision mediump float;
// Passed in from the vertex shader.
in vec2 v_texcoord;
// The texture.
uniform sampler2D u_texture;
// we need to declare an output for the fragment shader
out vec4 outColor;
void main() {
outColor = texture(u_texture, v_texcoord);
}
`;
function main() {
// Get A WebGL context
/** @type {HTMLCanvasElement} */
var canvas = document.getElementById("canvas");
var gl = canvas.getContext("webgl2", {
antialias: false
});
if (!gl) {
return;
}
// Use our boilerplate utils to compile the shaders and link into a program
var program = webglUtils.createProgramFromSources(gl, [vertexShaderSource, fragmentShaderSource]);
// look up where the vertex data needs to go.
var positionAttributeLocation = gl.getAttribLocation(program, "a_position");
var texcoordAttributeLocation = gl.getAttribLocation(program, "a_texcoord");
// look up uniform locations
var matrixLocation = gl.getUniformLocation(program, "u_matrix");
var textureLocation = gl.getUniformLocation(program, "u_texture");
// Create a buffer
var positionBuffer = gl.createBuffer();
// Create a vertex array object (attribute state)
var vao = gl.createVertexArray();
// and make it the one we're currently working with
gl.bindVertexArray(vao);
// Turn on the attribute
gl.enableVertexAttribArray(positionAttributeLocation);
// Bind it to ARRAY_BUFFER (think of it as ARRAY_BUFFER = positionBuffer)
gl.bindBuffer(gl.ARRAY_BUFFER, positionBuffer);
// Set Geometry.
setGeometry(gl);
// Tell the attribute how to get data out of positionBuffer (ARRAY_BUFFER)
var size = 3; // 3 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(
positionAttributeLocation, size, type, normalize, stride, offset);
// create the texcoord buffer, make it the current ARRAY_BUFFER
// and copy in the texcoord values
var texcoordBuffer = gl.createBuffer();
gl.bindBuffer(gl.ARRAY_BUFFER, texcoordBuffer);
setTexcoords(gl);
// Turn on the attribute
gl.enableVertexAttribArray(texcoordAttributeLocation);
// Tell the attribute how to get data out of colorBuffer (ARRAY_BUFFER)
var size = 2; // 2 components per iteration
var type = gl.FLOAT; // the data is 32bit floating point values
var normalize = true; // convert from 0-255 to 0.0-1.0
var stride = 0; // 0 = move forward size * sizeof(type) each iteration to get the next color
var offset = 0; // start at the beginning of the buffer
gl.vertexAttribPointer(
texcoordAttributeLocation, size, type, normalize, stride, offset);
// Create a texture.
var texture = gl.createTexture();
// use texture unit 0
gl.activeTexture(gl.TEXTURE0 + 0);
// bind to the TEXTURE_2D bind point of texture unit 0
gl.bindTexture(gl.TEXTURE_2D, texture);
// fill texture with 3x2 pixels
{
const level = 0;
const internalFormat = gl.R8;
const width = 3;
const height = 2;
const border = 0;
const format = gl.RED;
const type = gl.UNSIGNED_BYTE;
const data = new Uint8Array([
128, 64, 128,
0, 192, 0,
]);
gl.pixelStorei(gl.UNPACK_ALIGNMENT, 1);
gl.texImage2D(gl.TEXTURE_2D, level, internalFormat, width, height, border,
format, type, data);
}
// set the filtering so we don't need mips
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 texture to render to
const targetTextureWidth = 512;
const targetTextureHeight = 512;
const targetTexture = gl.createTexture();
gl.bindTexture(gl.TEXTURE_2D, targetTexture);
{
// define size and format of level 0
const level = 0;
const internalFormat = gl.RGBA;
const border = 0;
const format = gl.RGBA;
const type = gl.UNSIGNED_BYTE;
const data = null;
gl.texImage2D(gl.TEXTURE_2D, level, internalFormat,
targetTextureWidth, targetTextureHeight, border,
format, type, data);
// set the filtering so we don't need mips
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
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 and bind the framebuffer
const FRAMEBUFFER = {
RENDERBUFFER: 0,
COLORBUFFER: 1
};
const fb = [gl.createFramebuffer(), gl.createFramebuffer()];
const colorRenderbuffer = gl.createRenderbuffer();
gl.bindRenderbuffer(gl.RENDERBUFFER, colorRenderbuffer);
gl.renderbufferStorageMultisample(gl.RENDERBUFFER, gl.getParameter(gl.MAX_SAMPLES), gl.RGBA8, targetTextureWidth, targetTextureHeight);
gl.bindFramebuffer(gl.FRAMEBUFFER, fb[FRAMEBUFFER.RENDERBUFFER]);
gl.framebufferRenderbuffer(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.RENDERBUFFER, colorRenderbuffer);
gl.bindFramebuffer(gl.FRAMEBUFFER, fb[FRAMEBUFFER.COLORBUFFER]);
gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, targetTexture, 0);
gl.bindFramebuffer(gl.FRAMEBUFFER, null);
function degToRad(d) {
return d * Math.PI / 180;
}
var fieldOfViewRadians = degToRad(60);
var modelXRotationRadians = degToRad(0);
var modelYRotationRadians = degToRad(0);
// Get the starting time.
var then = 0;
requestAnimationFrame(drawScene);
function drawCube(aspect) {
// Tell it to use our program (pair of shaders)
gl.useProgram(program);
// Bind the attribute/buffer set we want.
gl.bindVertexArray(vao);
// Compute the projection matrix
var projectionMatrix =
m4.perspective(fieldOfViewRadians, aspect, 1, 2000);
var cameraPosition = [0, 0, 2];
var up = [0, 1, 0];
var target = [0, 0, 0];
// Compute the camera's matrix using look at.
var cameraMatrix = m4.lookAt(cameraPosition, target, up);
// Make a view matrix from the camera matrix.
var viewMatrix = m4.inverse(cameraMatrix);
var viewProjectionMatrix = m4.multiply(projectionMatrix, viewMatrix);
var matrix = m4.xRotate(viewProjectionMatrix, modelXRotationRadians);
matrix = m4.yRotate(matrix, modelYRotationRadians);
// Set the matrix.
gl.uniformMatrix4fv(matrixLocation, false, matrix);
// Tell the shader to use texture unit 0 for u_texture
gl.uniform1i(textureLocation, 0);
// Draw the geometry.
var primitiveType = gl.TRIANGLES;
var offset = 0;
var count = 6 * 6;
gl.drawArrays(primitiveType, offset, count);
}
// Draw the scene.
function drawScene(time) {
// convert to seconds
time *= 0.001;
// Subtract the previous time from the current time
var deltaTime = time - then;
// Remember the current time for the next frame.
then = time;
// Animate the rotation
modelYRotationRadians += -0.7 * deltaTime;
modelXRotationRadians += -0.4 * deltaTime;
//webglUtils.resizeCanvasToDisplaySize(gl.canvas);
gl.enable(gl.CULL_FACE);
gl.enable(gl.DEPTH_TEST);
{
// render to our targetTexture by binding the framebuffer
gl.bindFramebuffer(gl.FRAMEBUFFER, fb[FRAMEBUFFER.RENDERBUFFER]);
// render cube with our 3x2 texture
gl.bindTexture(gl.TEXTURE_2D, texture);
// Tell WebGL how to convert from clip space to pixels
gl.viewport(0, 0, targetTextureWidth, targetTextureHeight);
// Clear the canvas AND the depth buffer.
gl.clearColor(0, 0, 1, 1); // clear to blue
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
const aspect = targetTextureWidth / targetTextureHeight;
drawCube(aspect);
// "blit" the cube into the color buffer, which adds antialiasing
gl.bindFramebuffer(gl.READ_FRAMEBUFFER, fb[FRAMEBUFFER.RENDERBUFFER]);
gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, fb[FRAMEBUFFER.COLORBUFFER]);
gl.clearBufferfv(gl.COLOR, 0, [1.0, 1.0, 1.0, 1.0]);
gl.blitFramebuffer(0, 0, targetTextureWidth, targetTextureHeight,
0, 0, targetTextureWidth, targetTextureHeight,
gl.COLOR_BUFFER_BIT, gl.LINEAR);
}
{
// render the top layer to the frame buffer as well
gl.bindFramebuffer(gl.FRAMEBUFFER, fb[FRAMEBUFFER.RENDERBUFFER]);
// render the cube with the texture we just rendered to
gl.bindTexture(gl.TEXTURE_2D, targetTexture);
// Tell WebGL how to convert from clip space to pixels
gl.viewport(0, 0, targetTextureWidth, targetTextureHeight);
// Clear the canvas AND the depth buffer.
gl.clearColor(0.105, 0.105, 0.105, 1); // clear to black
gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);
const aspect = 1;
drawCube(aspect);
// this time render to the default buffer, which is just canvas
gl.bindFramebuffer(gl.READ_FRAMEBUFFER, fb[FRAMEBUFFER.RENDERBUFFER]);
gl.bindFramebuffer(gl.DRAW_FRAMEBUFFER, null);
gl.clearBufferfv(gl.COLOR, 0, [1.0, 1.0, 1.0, 1.0]);
gl.blitFramebuffer(0, 0, canvas.width, canvas.height,
0, 0, canvas.width, canvas.height,
gl.COLOR_BUFFER_BIT, gl.LINEAR);
}
requestAnimationFrame(drawScene);
}
}
// Fill the buffer with the values that define a cube.
function setGeometry(gl) {
var positions = new Float32Array(
[-0.5, -0.5, -0.5, -0.5, 0.5, -0.5,
0.5, -0.5, -0.5, -0.5, 0.5, -0.5,
0.5, 0.5, -0.5,
0.5, -0.5, -0.5,
-0.5, -0.5, 0.5,
0.5, -0.5, 0.5, -0.5, 0.5, 0.5, -0.5, 0.5, 0.5,
0.5, -0.5, 0.5,
0.5, 0.5, 0.5,
-0.5, 0.5, -0.5, -0.5, 0.5, 0.5,
0.5, 0.5, -0.5, -0.5, 0.5, 0.5,
0.5, 0.5, 0.5,
0.5, 0.5, -0.5,
-0.5, -0.5, -0.5,
0.5, -0.5, -0.5, -0.5, -0.5, 0.5, -0.5, -0.5, 0.5,
0.5, -0.5, -0.5,
0.5, -0.5, 0.5,
-0.5, -0.5, -0.5, -0.5, -0.5, 0.5, -0.5, 0.5, -0.5, -0.5, -0.5, 0.5, -0.5, 0.5, 0.5, -0.5, 0.5, -0.5,
0.5, -0.5, -0.5,
0.5, 0.5, -0.5,
0.5, -0.5, 0.5,
0.5, -0.5, 0.5,
0.5, 0.5, -0.5,
0.5, 0.5, 0.5,
]);
gl.bufferData(gl.ARRAY_BUFFER, positions, gl.STATIC_DRAW);
}
// Fill the buffer with texture coordinates the cube.
function setTexcoords(gl) {
gl.bufferData(
gl.ARRAY_BUFFER,
new Float32Array(
[
0, 0,
0, 1,
1, 0,
0, 1,
1, 1,
1, 0,
0, 0,
0, 1,
1, 0,
1, 0,
0, 1,
1, 1,
0, 0,
0, 1,
1, 0,
0, 1,
1, 1,
1, 0,
0, 0,
0, 1,
1, 0,
1, 0,
0, 1,
1, 1,
0, 0,
0, 1,
1, 0,
0, 1,
1, 1,
1, 0,
0, 0,
0, 1,
1, 0,
1, 0,
0, 1,
1, 1,
]),
gl.STATIC_DRAW);
}
main();
html
{
background-color: #1b1b1b;
}
<canvas id="canvas" width="512" height="512"></canvas>
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