如何在SketchGL中绘制全屏背景图像？
我知道如何绘制模型，但我不知道如何绘制全屏背景图像。
我想我应该在相机的zfar上画它。但我不知道如何计算它的大小...
在sketchfab中，背景图像似乎可以实现css属性background-size: cover。我注意到sketchfab没有用css来实现它。
我真的想知道如何实现这个！
1 个答案:
答案 0 :(得分：2)
如何在WebGL中绘制全屏背景图像，如样式
background-size: cover？
创建一个绘制纹理的简单着色器，不进行任何转换：
顶点着色器：
precision mediump float;
attribute vec2 inPos;
varying vec2 vertPos;
void main()
{
vertPos = inPos;
gl_Position = vec4( inPos, 0.0, 1.0 );
}
片段着色器：
precision mediump float;
varying vec2 vertPos;
uniform sampler2D u_texture;
void main()
{
vec2 texCoord = vec2( vertPos.s, -vertPos.t ) * 0.5 + 0.5;
vec3 texColor = texture2D( u_texture, texCoord.st ).rgb;
gl_FragColor = vec4( texColor.rgb, 1.0 );
}
创建一个数组缓冲区，其中包含XY平面的4个角点，归一化设备空间，从（-1，-1）到（1,1）。
bufRect = gl.createBuffer()
gl.bindBuffer( gl.ARRAY_BUFFER, bufRect );
gl.bufferData( gl.ARRAY_BUFFER, new Float32Array( [ -1, -1, 1, -1, 1, 1, -1, 1 ] ), gl.STATIC_DRAW );
使用着色器将矩形绘制到整个画布。由于您在每个片段上绘制，因此无需清除颜色平面。但是你必须禁用深度测试。
gl.disable( gl.DEPTH_TEST );
var texUnit = 1;
gl.activeTexture( gl.TEXTURE0 + texUnit );
gl.bindTexture( gl.TEXTURE_2D, textureObj );
var tex_loc = gl.getUniformLocation( progBG, "u_texture" );
gl.useProgram( progBG );
gl.uniform1i( tex_loc, texUnit );
var v_attr_inx = gl.getAttribLocation( progBG, "inPos" );
gl.bindBuffer( gl.ARRAY_BUFFER, bufRect );
gl.vertexAttribPointer( v_attr_inx, 2, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( v_attr_inx );
gl.drawArrays( gl.TRIANGLE_FAN, 0, 4 );
gl.disableVertexAttribArray( v_attr_inx );
在绘制场景的几何图形之前启用深度测试并清除深度缓冲区：
gl.clear( gl.DEPTH_BUFFER_BIT );
gl.enable( gl.DEPTH_TEST );
.....
注意，当你加载纹理时，你必须确保纹理的宽度和高度是2的幂。
var Texture = {};
Texture.HandleLoadedTexture2D = function( image, texture, flipY ) {
gl.activeTexture( gl.TEXTURE0 );
gl.bindTexture( gl.TEXTURE_2D, texture );
gl.texImage2D( gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image );
if ( flipY != undefined && flipY == true )
gl.pixelStorei( gl.UNPACK_FLIP_Y_WEBGL, true );
gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR );
gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR );
gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.REPEAT );
gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.REPEAT );
gl.bindTexture( gl.TEXTURE_2D, null );
return texture;
}
Texture.LoadTexture2D = function( name ) {
var texture = gl.createTexture();
texture.image = new Image(64,64);
texture.image.setAttribute('crossorigin', 'anonymous');
texture.image.onload = function () {
var canvas = document.createElement( 'canvas' );
canvas.width = 512;
canvas.height = 256;
var context = canvas.getContext( '2d' );
context.drawImage( texture.image, 0, 0, canvas.width, canvas.height );
Texture.HandleLoadedTexture2D( canvas, texture, true )
}
texture.image.src = name;
return texture;
}
textureObj = Texture.LoadTexture2D( "my_background_texture" );
请参阅代码段：
＆＃13;
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＆＃13;
glArrayType = typeof Float32Array !="undefined" ? Float32Array : ( typeof WebGLFloatArray != "undefined" ? WebGLFloatArray : Array );
function IdentityMat44() {
var m = new glArrayType(16);
m[0] = 1; m[1] = 0; m[2] = 0; m[3] = 0;
m[4] = 0; m[5] = 1; m[6] = 0; m[7] = 0;
m[8] = 0; m[9] = 0; m[10] = 1; m[11] = 0;
m[12] = 0; m[13] = 0; m[14] = 0; m[15] = 1;
return m;
};
function RotateAxis(matA, angRad, axis) {
var aMap = [ [1, 2], [2, 0], [0, 1] ];
var a0 = aMap[axis][0], a1 = aMap[axis][1];
var sinAng = Math.sin(angRad), cosAng = Math.cos(angRad);
var matB = new glArrayType(16);
for ( var i = 0; i < 16; ++ i ) matB[i] = matA[i];
for ( var i = 0; i < 3; ++ i ) {
matB[a0*4+i] = matA[a0*4+i] * cosAng + matA[a1*4+i] * sinAng;
matB[a1*4+i] = matA[a0*4+i] * -sinAng + matA[a1*4+i] * cosAng;
}
return matB;
}
function Cross( a, b ) { return [ a[1] * b[2] - a[2] * b[1], a[2] * b[0] - a[0] * b[2], a[0] * b[1] - a[1] * b[0], 0.0 ]; }
function Dot( a, b ) { return a[0]*b[0] + a[1]*b[1] + a[2]*b[2]; }
function Normalize( v ) {
var len = Math.sqrt( v[0] * v[0] + v[1] * v[1] + v[2] * v[2] );
return [ v[0] / len, v[1] / len, v[2] / len ];
}
var Camera = {};
Camera.create = function() {
this.pos = [0, 5, 0.0];
this.target = [0, 0, 0];
this.up = [0, 0, 1];
this.fov_y = 90;
this.vp = [800, 600];
this.near = 0.5;
this.far = 100.0;
}
Camera.Perspective = function() {
var fn = this.far + this.near;
var f_n = this.far - this.near;
var r = this.vp[0] / this.vp[1];
var t = 1 / Math.tan( Math.PI * this.fov_y / 360 );
var m = IdentityMat44();
m[0] = t/r; m[1] = 0; m[2] = 0; m[3] = 0;
m[4] = 0; m[5] = t; m[6] = 0; m[7] = 0;
m[8] = 0; m[9] = 0; m[10] = -fn / f_n; m[11] = -1;
m[12] = 0; m[13] = 0; m[14] = -2 * this.far * this.near / f_n; m[15] = 0;
return m;
}
Camera.LookAt = function() {
var mz = Normalize( [ this.pos[0]-this.target[0], this.pos[1]-this.target[1], this.pos[2]-this.target[2] ] );
var mx = Normalize( Cross( this.up, mz ) );
var my = Normalize( Cross( mz, mx ) );
var tx = Dot( mx, this.pos );
var ty = Dot( my, this.pos );
var tz = Dot( [-mz[0], -mz[1], -mz[2]], this.pos );
var m = IdentityMat44();
m[0] = mx[0]; m[1] = my[0]; m[2] = mz[0]; m[3] = 0;
m[4] = mx[1]; m[5] = my[1]; m[6] = mz[1]; m[7] = 0;
m[8] = mx[2]; m[9] = my[2]; m[10] = mz[2]; m[11] = 0;
m[12] = tx; m[13] = ty; m[14] = tz; m[15] = 1;
return m;
}
var ShaderProgram = {};
ShaderProgram.Create = function( shaderList ) {
var shaderObjs = [];
for ( var i_sh = 0; i_sh < shaderList.length; ++ i_sh ) {
var shderObj = this.CompileShader( shaderList[i_sh].source, shaderList[i_sh].stage );
if ( shderObj == 0 )
return 0;
shaderObjs.push( shderObj );
}
var progObj = this.LinkProgram( shaderObjs )
if ( progObj != 0 ) {
progObj.attribIndex = {};
var noOfAttributes = gl.getProgramParameter( progObj, gl.ACTIVE_ATTRIBUTES );
for ( var i_n = 0; i_n < noOfAttributes; ++ i_n ) {
var name = gl.getActiveAttrib( progObj, i_n ).name;
progObj.attribIndex[name] = gl.getAttribLocation( progObj, name );
}
progObj.unifomLocation = {};
var noOfUniforms = gl.getProgramParameter( progObj, gl.ACTIVE_UNIFORMS );
for ( var i_n = 0; i_n < noOfUniforms; ++ i_n ) {
var name = gl.getActiveUniform( progObj, i_n ).name;
progObj.unifomLocation[name] = gl.getUniformLocation( progObj, name );
}
}
return progObj;
}
ShaderProgram.AttributeIndex = function( progObj, name ) { return progObj.attribIndex[name]; }
ShaderProgram.UniformLocation = function( progObj, name ) { return progObj.unifomLocation[name]; }
ShaderProgram.Use = function( progObj ) { gl.useProgram( progObj ); }
ShaderProgram.SetUniformI1 = function( progObj, name, val ) { if(progObj.unifomLocation[name]) gl.uniform1i( progObj.unifomLocation[name], val ); }
ShaderProgram.SetUniformF1 = function( progObj, name, val ) { if(progObj.unifomLocation[name]) gl.uniform1f( progObj.unifomLocation[name], val ); }
ShaderProgram.SetUniformF2 = function( progObj, name, arr ) { if(progObj.unifomLocation[name]) gl.uniform2fv( progObj.unifomLocation[name], arr ); }
ShaderProgram.SetUniformF3 = function( progObj, name, arr ) { if(progObj.unifomLocation[name]) gl.uniform3fv( progObj.unifomLocation[name], arr ); }
ShaderProgram.SetUniformF4 = function( progObj, name, arr ) { if(progObj.unifomLocation[name]) gl.uniform4fv( progObj.unifomLocation[name], arr ); }
ShaderProgram.SetUniformM33 = function( progObj, name, mat ) { if(progObj.unifomLocation[name]) gl.uniformMatrix3fv( progObj.unifomLocation[name], false, mat ); }
ShaderProgram.SetUniformM44 = function( progObj, name, mat ) { if(progObj.unifomLocation[name]) gl.uniformMatrix4fv( progObj.unifomLocation[name], false, mat ); }
ShaderProgram.CompileShader = function( source, shaderStage ) {
var shaderScript = document.getElementById(source);
if (shaderScript) {
source = "";
var node = shaderScript.firstChild;
while (node) {
if (node.nodeType == 3) source += node.textContent;
node = node.nextSibling;
}
}
var shaderObj = gl.createShader( shaderStage );
gl.shaderSource( shaderObj, source );
gl.compileShader( shaderObj );
var status = gl.getShaderParameter( shaderObj, gl.COMPILE_STATUS );
if ( !status ) alert(gl.getShaderInfoLog(shaderObj));
return status ? shaderObj : 0;
}
ShaderProgram.LinkProgram = function( shaderObjs ) {
var prog = gl.createProgram();
for ( var i_sh = 0; i_sh < shaderObjs.length; ++ i_sh )
gl.attachShader( prog, shaderObjs[i_sh] );
gl.linkProgram( prog );
status = gl.getProgramParameter( prog, gl.LINK_STATUS );
if ( !status ) alert("Could not initialise shaders");
gl.useProgram( null );
return status ? prog : 0;
}
var VertexBuffer = {};
VertexBuffer.Create = function( attributes, indices ) {
var buffer = {};
buffer.buf = [];
buffer.attr = []
for ( var i = 0; i < attributes.length; ++ i ) {
buffer.buf.push( gl.createBuffer() );
buffer.attr.push( { size : attributes[i].attrSize, loc : attributes[i].attrLoc } );
gl.bindBuffer( gl.ARRAY_BUFFER, buffer.buf[i] );
gl.bufferData( gl.ARRAY_BUFFER, new Float32Array( attributes[i].data ), gl.STATIC_DRAW );
}
buffer.inx = gl.createBuffer();
gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, buffer.inx );
gl.bufferData( gl.ELEMENT_ARRAY_BUFFER, new Uint16Array( indices ), gl.STATIC_DRAW );
buffer.inxLen = indices.length;
gl.bindBuffer( gl.ARRAY_BUFFER, null );
gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, null );
return buffer;
}
VertexBuffer.Draw = function( bufObj ) {
for ( var i = 0; i < bufObj.buf.length; ++ i ) {
gl.bindBuffer( gl.ARRAY_BUFFER, bufObj.buf[i] );
gl.vertexAttribPointer( bufObj.attr[i].loc, bufObj.attr[i].size, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( bufObj.attr[i].loc );
}
gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, bufObj.inx );
gl.drawElements( gl.TRIANGLES, bufObj.inxLen, gl.UNSIGNED_SHORT, 0 );
for ( var i = 0; i < bufObj.buf.length; ++ i )
gl.disableVertexAttribArray( bufObj.attr[i].loc );
gl.bindBuffer( gl.ARRAY_BUFFER, null );
gl.bindBuffer( gl.ELEMENT_ARRAY_BUFFER, null );
}
var Texture = {};
Texture.HandleLoadedTexture2D = function( image, texture, flipY ) {
gl.activeTexture( gl.TEXTURE0 );
gl.bindTexture( gl.TEXTURE_2D, texture );
gl.texImage2D( gl.TEXTURE_2D, 0, gl.RGBA, gl.RGBA, gl.UNSIGNED_BYTE, image );
if ( flipY != undefined && flipY == true )
gl.pixelStorei( gl.UNPACK_FLIP_Y_WEBGL, true );
gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR );
gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR );
gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.REPEAT );
gl.texParameteri( gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.REPEAT );
gl.bindTexture( gl.TEXTURE_2D, null );
return texture;
}
Texture.LoadTexture2D = function( name ) {
var texture = gl.createTexture();
texture.image = new Image(64,64);
texture.image.setAttribute('crossorigin', 'anonymous');
texture.image.onload = function () {
var canvas = document.createElement( 'canvas' );
canvas.width = 512;
canvas.height = 256;
var context = canvas.getContext( '2d' );
context.drawImage( texture.image, 0, 0, canvas.width, canvas.height );
Texture.HandleLoadedTexture2D( canvas, texture, true )
}
texture.image.src = name;
return texture;
}
var ticks = 0;
function drawScene(){
var canvas = document.getElementById( "draw-canvas" );
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
Camera.create();
Camera.vp = [canvas.width, canvas.height];
var currentTime = Date.now();
var deltaMS = currentTime - startTime;
ticks = ticks + 1;
gl.viewport( 0, 0, canvas.width, canvas.height );
//gl.clearColor( 0.0, 0.0, 0.0, 0.0 );
gl.disable( gl.DEPTH_TEST );
var texUnit = 1;
gl.activeTexture( gl.TEXTURE0 + texUnit );
gl.bindTexture( gl.TEXTURE_2D, textureObj );
var tex_loc = gl.getUniformLocation( progBG, "u_texture" );
gl.useProgram( progBG );
gl.uniform1i( tex_loc, texUnit );
var v_attr_inx = gl.getAttribLocation( progBG, "inPos" );
gl.bindBuffer( gl.ARRAY_BUFFER, bufRect );
gl.vertexAttribPointer( v_attr_inx, 2, gl.FLOAT, false, 0, 0 );
gl.enableVertexAttribArray( v_attr_inx );
gl.drawArrays( gl.TRIANGLE_FAN, 0, 4 );
gl.disableVertexAttribArray( v_attr_inx );
// set up draw shader
ShaderProgram.Use( progDraw );
ShaderProgram.SetUniformM44( progDraw, "u_projectionMat44", Camera.Perspective() );
ShaderProgram.SetUniformM44( progDraw, "u_viewMat44", Camera.LookAt() );
var modelMat = IdentityMat44()
modelMat = RotateAxis( modelMat, CalcAng( currentTime, 13.0 ), 0 );
modelMat = RotateAxis( modelMat, CalcAng( currentTime, 17.0 ), 1 );
ShaderProgram.SetUniformM44( progDraw, "u_modelMat44", modelMat );
// draw scene
gl.clear( gl.DEPTH_BUFFER_BIT );
gl.enable( gl.DEPTH_TEST );
VertexBuffer.Draw( bufCube );
}
var startTime;
function Fract( val ) {
return val - Math.trunc( val );
}
function CalcAng( currentTime, intervall ) {
return Fract( (currentTime - startTime) / (1000*intervall) ) * 2.0 * Math.PI;
}
function CalcMove( currentTime, intervall, range ) {
var pos = self.Fract( (currentTime - startTime) / (1000*intervall) ) * 2.0
var pos = pos < 1.0 ? pos : (2.0-pos)
return range[0] + (range[1] - range[0]) * pos;
}
function EllipticalPosition( a, b, angRag ) {
var a_b = a * a - b * b
var ea = (a_b <= 0) ? 0 : Math.sqrt( a_b );
var eb = (a_b >= 0) ? 0 : Math.sqrt( -a_b );
return [ a * Math.sin( angRag ) - ea, b * Math.cos( angRag ) - eb, 0 ];
}
var sliderScale = 100.0
var gl;
var progDraw, progBG;
var bufCube = {};
var bufRect = {};
function sceneStart() {
var canvas = document.getElementById( "draw-canvas");
canvas.width = window.innerWidth;
canvas.height = window.innerHeight;
var vp = [canvas.width, canvas.height];
gl = canvas.getContext( "experimental-webgl" );
if ( !gl )
return;
progBG = ShaderProgram.Create(
[ { source : "background-shader-vs", stage : gl.VERTEX_SHADER },
{ source : "background-shader-fs", stage : gl.FRAGMENT_SHADER }
] );
progBG.inPos = gl.getAttribLocation( progBG, "inPos" );
if ( progBG == 0 )
return;
progDraw = ShaderProgram.Create(
[ { source : "draw-shader-vs", stage : gl.VERTEX_SHADER },
{ source : "draw-shader-fs", stage : gl.FRAGMENT_SHADER }
] );
progDraw.inPos = gl.getAttribLocation( progDraw, "inPos" );
progDraw.inCol = gl.getAttribLocation( progDraw, "inCol" );
if ( progDraw == 0 )
return;
//textureObj = Texture.LoadTexture2D( "https://raw.githubusercontent.com/Rabbid76/graphics-snippets/master/resource/texture/supermario.jpg" );
textureObj = Texture.LoadTexture2D( "https://raw.githubusercontent.com/Rabbid76/graphics-snippets/master/resource/texture/background.jpg" );
bufRect = gl.createBuffer()
gl.bindBuffer( gl.ARRAY_BUFFER, bufRect );
gl.bufferData( gl.ARRAY_BUFFER, new Float32Array( [ -1, -1, 1, -1, 1, 1, -1, 1 ] ), gl.STATIC_DRAW );
// create cube
var cubePos = [
-1.0, -1.0, 1.0, 1.0, -1.0, 1.0, 1.0, 1.0, 1.0, -1.0, 1.0, 1.0,
-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 cubeCol = [ 1.0, 0.0, 0.0, 1.0, 0.5, 0.0, 1.0, 0.0, 1.0, 1.0, 1.0, 0.0, 0.0, 1.0, 0.0, 0.0, 0.0, 1.0 ];
var cubeHlpInx = [ 0, 1, 2, 3, 1, 5, 6, 2, 5, 4, 7, 6, 4, 0, 3, 7, 3, 2, 6, 7, 1, 0, 4, 5 ];
var cubePosData = [];
for ( var i = 0; i < cubeHlpInx.length; ++ i ) {
cubePosData.push( cubePos[cubeHlpInx[i]*3], cubePos[cubeHlpInx[i]*3+1], cubePos[cubeHlpInx[i]*3+2] );
}
var cubeNVData = [];
for ( var i1 = 0; i1 < cubeHlpInx.length; i1 += 4 ) {
var nv = [0, 0, 0];
for ( i2 = 0; i2 < 4; ++ i2 ) {
var i = i1 + i2;
nv[0] += cubePosData[i*3]; nv[1] += cubePosData[i*3+1]; nv[2] += cubePosData[i*3+2];
}
for ( i2 = 0; i2 < 4; ++ i2 )
cubeNVData.push( nv[0], nv[1], nv[2] );
}
var cubeColData = [];
for ( var is = 0; is < 6; ++ is ) {
for ( var ip = 0; ip < 4; ++ ip ) {
cubeColData.push( cubeCol[is*3], cubeCol[is*3+1], cubeCol[is*3+2] );
}
}
var cubeInxData = [];
for ( var i = 0; i < cubeHlpInx.length; i += 4 ) {
cubeInxData.push( i, i+1, i+2, i, i+2, i+3 );
}
bufCube = VertexBuffer.Create(
[ { data : cubePosData, attrSize : 3, attrLoc : progDraw.inPos },
//{ data : cubeNVData, attrSize : 3, attrLoc : progDraw.inNV },
{ data : cubeColData, attrSize : 3, attrLoc : progDraw.inCol } ],
cubeInxData );
startTime = Date.now();
setInterval(drawScene, 50);
}<script id="background-shader-vs" type="x-shader/x-vertex">
precision mediump float;
attribute vec2 inPos;
varying vec2 vertPos;
void main()
{
vertPos = inPos;
gl_Position = vec4( inPos, 0.0, 1.0 );
}
</script>
<script id="background-shader-fs" type="x-shader/x-fragment">
precision mediump float;
varying vec2 vertPos;
uniform sampler2D u_texture;
void main()
{
vec2 texCoord = vec2( vertPos.s, -vertPos.t ) * 0.5 + 0.5;
vec3 texColor = texture2D( u_texture, texCoord.st ).rgb;
gl_FragColor = vec4( texColor.rgb, 1.0 );
}
</script>
<script id="draw-shader-vs" type="x-shader/x-vertex">
precision mediump float;
attribute vec3 inPos;
attribute vec3 inCol;
varying vec3 vertCol;
uniform mat4 u_projectionMat44;
uniform mat4 u_viewMat44;
uniform mat4 u_modelMat44;
void main()
{
vertCol = inCol;
vec4 modelPos = u_modelMat44 * vec4( inPos, 1.0 );
vec4 viewPos = u_viewMat44 * modelPos;
gl_Position = u_projectionMat44 * viewPos;
}
</script>
<script id="draw-shader-fs" type="x-shader/x-fragment">
precision mediump float;
varying vec3 vertCol;
void main()
{
gl_FragColor = vec4( vertCol.rgb, 1.0 );
}
</script>
<body onload="sceneStart();">
<canvas id="draw-canvas" style="border: none;" width="100%" height="100%"></canvas>
</body>
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