学习texturedCube.ts
最终渲染结果:
该示例绘制了有一个纹理的立方体。
与“rotatingCube”示例相比,该示例增加了下面的步骤:
- 传输顶点的uv数据
- 增加了sampler和sampled-texture类型的uniform数据
下面,我们打开texturedCube.ts文件,依次分析增加的步骤:
传递顶点的uv数据
- shader加入uv attribute
代码如下:
const vertexShaderGLSL = `#version 450 ... layout(location = 0) in vec4 position; layout(location = 1) in vec2 uv; layout(location = 0) out vec2 fragUV; layout(location = 1) out vec4 fragPosition; void main() { fragPosition = 0.5 * (position + vec4(1.0)); ... fragUV = uv; } `; const fragmentShaderGLSL = `#version 450 layout(set = 0, binding = 1) uniform sampler mySampler; layout(set = 0, binding = 2) uniform texture2D myTexture; layout(location = 0) in vec2 fragUV; layout(location = 1) in vec4 fragPosition; layout(location = 0) out vec4 outColor; void main() { outColor = texture(sampler2D(myTexture, mySampler), fragUV) * fragPosition; } `;
vertex shader传入了uv attribute数据,并将其传递给fragUV,从而传到fragment shader,作为纹理采样坐标
另外,这里可以顺便说明下:fragPosition用来实现与position相关的颜色渐变效果
- uv数据包含在verticesBuffer的cubeVertexArray中
cubeVertexArray的代码如下:
cube.ts: export const cubeUVOffset = 4 * 8; export const cubeVertexArray = new Float32Array([ // float4 position, float4 color, float2 uv, 1, -1, 1, 1, 1, 0, 1, 1, 1, 1, -1, -1, 1, 1, 0, 0, 1, 1, 0, 1, -1, -1, -1, 1, 0, 0, 0, 1, 0, 0, 1, -1, -1, 1, 1, 0, 0, 1, 1, 0, 1, -1, 1, 1, 1, 0, 1, 1, 1, 1, -1, -1, -1, 1, 0, 0, 0, 1, 0, 0, ... ]);
创建和设置verticesBuffer的相关代码如下:
texturedCube.ts: const verticesBuffer = device.createBuffer({ size: cubeVertexArray.byteLength, usage: GPUBufferUsage.VERTEX | GPUBufferUsage.COPY_DST }); verticesBuffer.setSubData(0, cubeVertexArray); ... return function frame() { ... passEncoder.setVertexBuffer(0, verticesBuffer); ... }
- 创建render pipeline时指定uv attribute的相关数据
代码如下:
const pipeline = device.createRenderPipeline({ ... vertexState: { vertexBuffers: [{ ... attributes: [ ... { // uv shaderLocation: 1, offset: cubeUVOffset, format: "float2" }] }], }, ... });
增加了sampler和sampled-texture类型的uniform数据
WebGPU相对于WebGL1,提出了sampler,可以对它设置filter、wrap等参数,从而实现了texture和sampler自由组合,同一个texture能够以不同filter、wrap来采样
- fragment shader传入这两个uniform数据,用于纹理采样
代码如下:
const fragmentShaderGLSL = `#version 450 layout(set = 0, binding = 1) uniform sampler mySampler; layout(set = 0, binding = 2) uniform texture2D myTexture; layout(location = 0) in vec2 fragUV; layout(location = 1) in vec4 fragPosition; layout(location = 0) out vec4 outColor; void main() { outColor = texture(sampler2D(myTexture, mySampler), fragUV) * fragPosition; } `;
- 创建bind group layout时指定它们在shader中的binding位置等参数
代码如下:
const bindGroupLayout = device.createBindGroupLayout({ bindings: [ ... { // Sampler binding: 1, visibility: GPUShaderStage.FRAGMENT, type: "sampler" }, { // Texture view binding: 2, visibility: GPUShaderStage.FRAGMENT, type: "sampled-texture" }] });
- 拷贝图片到texture,返回texture
代码如下,后面会进一步研究:
const cubeTexture = await createTextureFromImage(device, 'assets/img/Di-3d.png', GPUTextureUsage.SAMPLED);
- 创建sampler,指定filter
代码如下:
const sampler = device.createSampler({ magFilter: "linear", minFilter: "linear", });
我们看一下相关定义:
GPUSampler createSampler(optional GPUSamplerDescriptor descriptor = {}); ... dictionary GPUSamplerDescriptor : GPUObjectDescriptorBase { GPUAddressMode addressModeU = "clamp-to-edge"; GPUAddressMode addressModeV = "clamp-to-edge"; GPUAddressMode addressModeW = "clamp-to-edge"; GPUFilterMode magFilter = "nearest"; GPUFilterMode minFilter = "nearest"; GPUFilterMode mipmapFilter = "nearest"; float lodMinClamp = 0; float lodMaxClamp = 0xffffffff; GPUCompareFunction compare = "never"; };
GPUSamplerDescriptor的addressMode指定了texture在u、v、w方向的wrap mode(u、v方向的wrap相当于WebGL1的wrapS、wrapT)(w方向是给3d texture用的)
mipmapFilter与mipmap有关,lodXXX与texture lod有关,compare与软阴影的Percentage Closer Filtering技术有关,我们不讨论它们
- 创建uniform bind group时传入sampler和texture的view
const uniformBindGroup = device.createBindGroup({ layout: bindGroupLayout, bindings: [ ... { binding: 1, resource: sampler, }, { binding: 2, resource: cubeTexture.createView(), }], });
参考资料
详细分析“拷贝图片到texture”步骤
相关代码如下:
const cubeTexture = await createTextureFromImage(device, 'assets/img/Di-3d.png', GPUTextureUsage.SAMPLED);
该步骤可以分解为两步:
1.解码图片
2.拷贝解码后的类型为HTMLImageElement的图片到GPU的texture中
下面依次分析:
解码图片
打开helper.ts文件,查看createTextureFromImage对应代码:
const img = document.createElement('img'); img.src = src; await img.decode();
这里使用decode api来解码图片,也可以使用img.onload来实现:
const img = document.createElement('img'); img.src = src; img.onload = (img) => { ... };
根据Pre-Loading and Pre-Decoding Images with Javascript for Better Performance的说法,图片的加载过程有两个步骤:
1.从服务器加载图片
2.解码图片
第1步都是在其它线程上并行执行;
如果用onload,则浏览器会在主线程上同步执行第2步,会阻塞主线程;
如果用decode api,则浏览器会在其它线程上并行执行第2步,不会阻塞主线程。
chrome和firefox浏览器都支持decode api,因此加载图片应该优先使用该API:
参考资料
Pre-Loading and Pre-Decoding Images with Javascript for Better Performance
拷贝图片
WebGL1直接使用texImage2D将图片上传到GPU texture中,而WebGPU能让我们更加灵活地控制上传过程。
WebGPU有两种方法上传:
- 创建图片对应的imageBitmap,将其拷贝到GPU texture中
该方法要用到copyImageBitmapToTexture函数。虽然WebGPU规范已经定义了该函数,但目前Chrome Canary不支持它,所以暂时不能用该方法上传。
参考资料
Proposal for copyImageBitmapToTexture
- 将图片绘制到canvas中,通过getImageData获得数据->将其设置到buffer中->把buffer数据拷贝到GPU texture中
我们来看下createTextureFromImage对应代码:
const imageCanvas = document.createElement('canvas'); imageCanvas.width = img.width; imageCanvas.height = img.height; const imageCanvasContext = imageCanvas.getContext('2d'); //flipY imageCanvasContext.translate(0, img.height); imageCanvasContext.scale(1, -1); imageCanvasContext.drawImage(img, 0, 0, img.width, img.height); const imageData = imageCanvasContext.getImageData(0, 0, img.width, img.height);
这里创建canvas->绘制图片->获得图片数据。
(注:在绘制图片时将图片在Y方向反转了)
接着看代码:
let data = null; const rowPitch = Math.ceil(img.width * 4 / 256) * 256; if (rowPitch == img.width * 4) { data = imageData.data; } else { data = new Uint8Array(rowPitch * img.height); for (let y = 0; y < img.height; ++y) { for (let x = 0; x < img.width; ++x) { let i = x * 4 + y * rowPitch; data[i] = imageData.data[i]; data[i + 1] = imageData.data[i + 1]; data[i + 2] = imageData.data[i + 2]; data[i + 3] = imageData.data[i + 3]; } } } const texture = device.createTexture({ size: { width: img.width, height: img.height, depth: 1, }, format: "rgba8unorm", usage: GPUTextureUsage.COPY_DST | usage, }); const textureDataBuffer = device.createBuffer({ size: data.byteLength, usage: GPUBufferUsage.COPY_DST | GPUBufferUsage.COPY_SRC, }); textureDataBuffer.setSubData(0, data);
rowPitch需要为256的倍数(也就是说,图片的宽度需要为64px的倍数),这是因为Dx12对此做了限制(参考Copies investigation):
RowPitch must be aligned to D3D12_TEXTURE_DATA_PITCH_ALIGNMENT.
Offset must be aligned to D3D12_TEXTURE_DATA_PLACEMENT_ALIGNMENT, which is 512.
另外,关于纹理尺寸,可以参考WebGPU-6:
第一个问题是关于纹理尺寸的,回答是WebGPU没有对尺寸有特别明确的要求。sample code中最多不能比4kor8k大就行。这个也不是太难理解,OpenGL对纹理和FBO的尺寸总是有上限的。
根据我的测试,buffer(代码中的textureDataBuffer)中的图片数据需要为未压缩的图片数据(它的类型为Uint8Array,length=img.width * img.height * 4(因为每个像素有r、g、b、a这4个值)),否则会报错(在我的测试中,“通过canvas->toDataURL得到图片的base64->将其转为Uint8Array,得到压缩后的图片数据->将其设置到buffer中”会报错)
继续看代码:
const commandEncoder = device.createCommandEncoder({}); commandEncoder.copyBufferToTexture({ buffer: textureDataBuffer, rowPitch: rowPitch, imageHeight: 0, }, { texture: texture, }, { width: img.width, height: img.height, depth: 1, }); device.defaultQueue.submit([commandEncoder.finish()]); return texture;
这里提交了copyBufferToTexture这个command到GPU,并返回texture
(注:这个command此时并没有执行,会由GPU决定什么时候执行)
WebGPU支持buffer与buffer、buffer与texture、texture与texture之间互相拷贝。
参考资料
Copies investigation (+ proposals)