问题
I am attempting to render a Uint16Array to an image in the browser using webgl2 textures. I have a working example fiddle of a Uint8Array and am struggling with the upgrade to 16bit as webgl has a steep learning curve.
Working 8-bit fiddle (identical to snippet below): Uint8Array http://jsfiddle.net/njxvftc9/2/
Non-working 16-bit attempt: Uint16Array http://jsfiddle.net/njxvftc9/3/
// image data
var w = 128;
var h = 128;
var size = w * h * 4;
var img = new Uint8Array(size); // need Uint16Array
for (var i = 0; i < img.length; i += 4) {
img[i + 0] = 255; // r
img[i + 1] = i/64; // g
img[i + 2] = 0; // b
img[i + 3] = 255; // a
}
// program
var canvas = document.getElementById('cv');
var gl = canvas.getContext('webgl2');
var program = gl.createProgram();
//var color_buffer_float_16ui = gl.getExtension('EXT_color_buffer_float'); // add for 16-bit
// texture
var tex = gl.createTexture(); // create empty texture
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
gl.texImage2D(
gl.TEXTURE_2D, // target
0, // mip level
gl.RGBA, // internal format -> gl.RGBA16UI
w, h, // width and height
0, // border
gl.RGBA, //format -> gm.RGBA_INTEGER
gl.UNSIGNED_BYTE, // type -> gl.UNSIGNED_SHORT
img // texture data
);
// buffer
var buffer = gl.createBuffer();
var bufferData = new Float32Array([
-1, -1,
1, -1,
1, 1,
1, 1,
-1, 1,
-1, -1
]);
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(gl.ARRAY_BUFFER, bufferData, gl.STATIC_DRAW);
// shaders
program.vs = gl.createShader(gl.VERTEX_SHADER);
gl.shaderSource(program.vs,
"attribute vec4 vertex;\n" + // incoming pixel input?
"varying vec2 pixelCoordinate;\n" + // variable used to pass position to fragment shader
"void main(){\n" +
" gl_Position = vertex;\n" + // set pixel output position to incoming position (pass through)
" pixelCoordinate = vertex.xy*0.5+0.5;\n" + // set coordinate for fragment shader
"}\n");
program.fs = gl.createShader(gl.FRAGMENT_SHADER);
gl.shaderSource(program.fs,
"precision highp float;\n" + // ?
"uniform sampler2D tex;\n" + // ?
"varying vec2 pixelCoordinate;\n" + // receive pixel position from vertex shader
"void main(){\n" +
" gl_FragColor = texture2D(tex, pixelCoordinate);\n" + // lookup color in texture image at coordinate position and set color to
"}\n");
gl.compileShader(program.vs);
gl.compileShader(program.fs);
gl.attachShader(program,program.vs);
gl.attachShader(program,program.fs);
gl.deleteShader(program.vs);
gl.deleteShader(program.fs);
// program
gl.bindAttribLocation(program, 0, "vertex");
gl.linkProgram(program);
gl.useProgram(program);
gl.enableVertexAttribArray(0);
gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.TRIANGLES, 0, 6); // execute program<canvas id="cv" width="100" height="100"></canvas>I have tried made many other techniques, referenced the spec, tried converting to floating point in the shaders, and have tried to combine methods seen here: Render to 16bits unsigned integer 2D texture in WebGL2 with no success.
I prefer vanilla js but am open to using libraries such as twgl or three.js as long as the input is a Uint16Array, the shaders can output any format (float, etc).
Can anyone with more experience in webgl2 point me in the right direction or provide a working sample fiddle here? Is there a simple mistake in my code, am I missing a larger concept, is this even possible? Any help is greatly appreciated!
回答1:
If you want to put 16bit data into a texture you need to choose a 16bit texture internal format. Looking at the list of internal formats your choices for RGBA are
gl.RGBA16I // 16bit integers
gl.RGBA16UI // 16bit unsigned integers
gl.RGBA16F // 16bit half floats
It looks like you choose gl.RGBA16UI
To access that texture in the shader this line
uniform sampler2D tex;
has to change this this
uniform usampler2D tex;
That syntax is only available with GLSL 3.00 es so you need to add #version 300 es to the top of both shaders.
Switching to #version 300 es also means other syntax changes. attribute becomes in, varying becomes out in a vertex shader and in in a fragment shader. gl_FragColor disappears and you have to declare your own output for example out vec4 fooColor;. Also texture2D becomes just texture
You can not using filtering on integer textures so these 2 lines
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
need to change to
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
And when you get data out of the texture it will be unsigned integers so this line
gl_FragColor = texture2D(tex, pixelCoordinate);
would end up changing to something like
out vec4 fooColor; // named this fooColor to make it clear you pick the name
void main() {
uvec4 unsignedIntValues = texture(tex, pixelCoordinate);
vec4 floatValues0To65535 = vec4(unsignedIntValues);
vec4 colorValues0To1 = floatValues0To65535 / 65535.0;
fooColor = colorValues0To1;
}
Of course you can shorten that math to a single line
fooColor = vec4(texture(tex, pixelCoordinate)) / 65535.0;
Example:
// image data
var w = 128;
var h = 128;
var size = w * h * 4;
var img = new Uint16Array(size); // need Uint16Array
for (var i = 0; i < img.length; i += 4) {
img[i + 0] = 65535; // r
img[i + 1] = i/64 * 256; // g
img[i + 2] = 0; // b
img[i + 3] = 65535; // a
}
// program
var canvas = document.getElementById('cv');
var gl = canvas.getContext('webgl2');
var program = gl.createProgram();
//var color_buffer_float_16ui = gl.getExtension('EXT_color_buffer_float'); // add for 16-bit
// texture
var tex = gl.createTexture(); // create empty texture
gl.bindTexture(gl.TEXTURE_2D, tex);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
gl.texImage2D(
gl.TEXTURE_2D, // target
0, // mip level
gl.RGBA16UI, // internal format -> gl.RGBA16UI
w, h, // width and height
0, // border
gl.RGBA_INTEGER, //format -> gm.RGBA_INTEGER
gl.UNSIGNED_SHORT, // type -> gl.UNSIGNED_SHORT
img // texture data
);
// buffer
var buffer = gl.createBuffer();
var bufferData = new Float32Array([
-1, -1,
1, -1,
1, 1,
1, 1,
-1, 1,
-1, -1
]);
gl.bindBuffer(gl.ARRAY_BUFFER, buffer);
gl.bufferData(gl.ARRAY_BUFFER, bufferData, gl.STATIC_DRAW);
// shaders
program.vs = gl.createShader(gl.VERTEX_SHADER);
gl.shaderSource(program.vs, `#version 300 es
in vec4 vertex; // incoming pixel input?
out vec2 pixelCoordinate; // variable used to pass position to fragment shader
void main(){
gl_Position = vertex; // set pixel output position to incoming position (pass through)
pixelCoordinate = vertex.xy*0.5+0.5; // set coordinate for fragment shader
}
`);
program.fs = gl.createShader(gl.FRAGMENT_SHADER);
gl.shaderSource(program.fs, `#version 300 es
precision highp float; // ?
uniform highp usampler2D tex; // ?
in vec2 pixelCoordinate; // receive pixel position from vertex shader
out vec4 fooColor;
void main() {
uvec4 unsignedIntValues = texture(tex, pixelCoordinate);
vec4 floatValues0To65535 = vec4(unsignedIntValues);
vec4 colorValues0To1 = floatValues0To65535 / 65535.0;
fooColor = colorValues0To1;
}
`);
gl.compileShader(program.vs);
checkCompileError(program.vs);
gl.compileShader(program.fs);
checkCompileError(program.fs);
function checkCompileError(s) {
if (!gl.getShaderParameter(s, gl.COMPILE_STATUS)) {
console.error(gl.getShaderInfoLog(s));
}
}
gl.attachShader(program,program.vs);
gl.attachShader(program,program.fs);
gl.deleteShader(program.vs);
gl.deleteShader(program.fs);
// program
gl.bindAttribLocation(program, 0, "vertex");
gl.linkProgram(program);
gl.useProgram(program);
gl.enableVertexAttribArray(0);
gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);
gl.clear(gl.COLOR_BUFFER_BIT);
gl.drawArrays(gl.TRIANGLES, 0, 6); // execute program<canvas id="cv" width="100" height="100"></canvas>来源：https://stackoverflow.com/questions/57699322/webgl2-render-uint16array-to-canvas-as-an-image