three
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JavaScript 3D library
789 lines (481 loc) • 17.5 kB
JavaScript
import { REVISION } from 'three/webgpu';
import { VariableDeclaration, Accessor } from './AST.js';
import { isExpression } from './TranspilerUtils.js';
// Note: This is a simplified list. A complete implementation would need more mappings.
const typeMap = {
'float': 'f32',
'int': 'i32',
'uint': 'u32',
'bool': 'bool',
'vec2': 'vec2f',
'ivec2': 'vec2i',
'uvec2': 'vec2u',
'bvec2': 'vec2b',
'vec3': 'vec3f',
'ivec3': 'vec3i',
'uvec3': 'vec3u',
'bvec3': 'vec3b',
'vec4': 'vec4f',
'ivec4': 'vec4i',
'uvec4': 'vec4u',
'bvec4': 'vec4b',
'mat3': 'mat3x3<f32>',
'mat4': 'mat4x4<f32>',
'texture': 'texture_2d<f32>',
'textureCube': 'texture_cube<f32>',
'texture3D': 'texture_3d<f32>',
};
// GLSL to WGSL built-in function mapping
const wgslLib = {
'abs': 'abs',
'acos': 'acos',
'asin': 'asin',
'atan': 'atan',
'atan2': 'atan2',
'ceil': 'ceil',
'clamp': 'clamp',
'cos': 'cos',
'cross': 'cross',
'degrees': 'degrees',
'distance': 'distance',
'dot': 'dot',
'exp': 'exp',
'exp2': 'exp2',
'faceforward': 'faceForward',
'floor': 'floor',
'fract': 'fract',
'inverse': 'inverse',
'inversesqrt': 'inverseSqrt',
'length': 'length',
'log': 'log',
'log2': 'log2',
'max': 'max',
'min': 'min',
'mix': 'mix',
'normalize': 'normalize',
'pow': 'pow',
'radians': 'radians',
'reflect': 'reflect',
'refract': 'refract',
'round': 'round',
'sign': 'sign',
'sin': 'sin',
'smoothstep': 'smoothstep',
'sqrt': 'sqrt',
'step': 'step',
'tan': 'tan',
'transpose': 'transpose',
'trunc': 'trunc',
'dFdx': 'dpdx',
'dFdy': 'dpdy',
'fwidth': 'fwidth',
// Texture functions are handled separately
'texture': 'textureSample',
'texture2D': 'textureSample',
'texture3D': 'textureSample',
'textureCube': 'textureSample',
'textureLod': 'textureSampleLevel',
'texelFetch': 'textureLoad',
'textureGrad': 'textureSampleGrad',
};
class WGSLEncoder {
constructor() {
this.tab = '';
this.functions = new Map();
this.uniforms = [];
this.varyings = [];
this.structs = new Map();
this.polyfills = new Map();
// Assume a single group for simplicity
this.groupIndex = 0;
}
getWgslType( type ) {
return typeMap[ type ] || type;
}
emitExpression( node ) {
if ( ! node ) return '';
let code;
if ( node.isAccessor ) {
// Check if this accessor is part of a uniform struct
const uniform = this.uniforms.find( u => u.name === node.property );
if ( uniform && ! uniform.type.includes( 'texture' ) ) {
return `uniforms.${node.property}`;
}
code = node.property;
} else if ( node.isNumber ) {
code = node.value;
// WGSL requires floating point numbers to have a decimal
if ( node.type === 'float' && ! code.includes( '.' ) ) {
code += '.0';
}
} else if ( node.isOperator ) {
const left = this.emitExpression( node.left );
const right = this.emitExpression( node.right );
code = `${ left } ${ node.type } ${ right }`;
if ( node.parent.isAssignment !== true && node.parent.isOperator ) {
code = `( ${ code } )`;
}
} else if ( node.isFunctionCall ) {
const fnName = wgslLib[ node.name ] || node.name;
if ( fnName === 'mod' ) {
const snippets = node.params.map( p => this.emitExpression( p ) );
const types = node.params.map( p => p.getType() );
const modFnName = 'mod_' + types.join( '_' );
if ( this.polyfills.has( modFnName ) === false ) {
this.polyfills.set( modFnName, `fn ${ modFnName }( x: ${ this.getWgslType( types[ 0 ] ) }, y: ${ this.getWgslType( types[ 1 ] ) } ) -> ${ this.getWgslType( types[ 0 ] ) } {
return x - y * floor( x / y );
}` );
}
code = `${ modFnName }( ${ snippets.join( ', ' ) } )`;
} else if ( fnName.startsWith( 'texture' ) ) {
// Handle texture functions separately due to sampler handling
code = this.emitTextureAccess( node );
} else {
const params = node.params.map( p => this.emitExpression( p ) );
if ( typeMap[ fnName ] ) {
// Handle type constructors like vec3(...)
code = this.getWgslType( fnName );
} else {
code = fnName;
}
if ( params.length > 0 ) {
code += '( ' + params.join( ', ' ) + ' )';
} else {
code += '()';
}
}
} else if ( node.isReturn ) {
code = 'return';
if ( node.value ) {
code += ' ' + this.emitExpression( node.value );
}
} else if ( node.isDiscard ) {
code = 'discard';
} else if ( node.isBreak ) {
if ( node.parent.isSwitchCase !== true ) {
code = 'break';
}
} else if ( node.isContinue ) {
code = 'continue';
} else if ( node.isAccessorElements ) {
code = this.emitExpression( node.object );
for ( const element of node.elements ) {
const value = this.emitExpression( element.value );
if ( element.isStaticElement ) {
code += '.' + value;
} else if ( element.isDynamicElement ) {
code += `[${value}]`;
}
}
} else if ( node.isFor ) {
code = this.emitFor( node );
} else if ( node.isWhile ) {
code = this.emitWhile( node );
} else if ( node.isSwitch ) {
code = this.emitSwitch( node );
} else if ( node.isVariableDeclaration ) {
code = this.emitVariables( node );
} else if ( node.isUniform ) {
this.uniforms.push( node );
return ''; // Defer emission to the header
} else if ( node.isVarying ) {
this.varyings.push( node );
return ''; // Defer emission to the header
} else if ( node.isTernary ) {
const cond = this.emitExpression( node.cond );
const left = this.emitExpression( node.left );
const right = this.emitExpression( node.right );
// WGSL's equivalent to the ternary operator is select(false_val, true_val, condition)
code = `select( ${ right }, ${ left }, ${ cond } )`;
} else if ( node.isConditional ) {
code = this.emitConditional( node );
} else if ( node.isUnary ) {
const expr = this.emitExpression( node.expression );
if ( node.type === '++' || node.type === '--' ) {
const op = node.type === '++' ? '+' : '-';
code = `${ expr } = ${ expr } ${ op } 1`;
} else {
code = `${ node.type }${ expr }`;
}
} else {
console.warn( 'Unknown node type in WGSL Encoder:', node );
code = `/* unknown node: ${ node.constructor.name } */`;
}
return code;
}
emitTextureAccess( node ) {
const wgslFn = wgslLib[ node.name ];
const textureName = this.emitExpression( node.params[ 0 ] );
const uv = this.emitExpression( node.params[ 1 ] );
// WGSL requires explicit samplers. We assume a naming convention.
const samplerName = `${textureName}_sampler`;
let code;
switch ( node.name ) {
case 'texture':
case 'texture2D':
case 'texture3D':
case 'textureCube':
// format: textureSample(texture, sampler, coords, [offset])
code = `${wgslFn}(${textureName}, ${samplerName}, ${uv}`;
// Handle optional bias parameter (note: WGSL uses textureSampleBias)
if ( node.params.length === 3 ) {
const bias = this.emitExpression( node.params[ 2 ] );
code = `textureSampleBias(${textureName}, ${samplerName}, ${uv}, ${bias})`;
} else {
code += ')';
}
break;
case 'textureLod':
// format: textureSampleLevel(texture, sampler, coords, level)
const lod = this.emitExpression( node.params[ 2 ] );
code = `${wgslFn}(${textureName}, ${samplerName}, ${uv}, ${lod})`;
break;
case 'textureGrad':
// format: textureSampleGrad(texture, sampler, coords, ddx, ddy)
const ddx = this.emitExpression( node.params[ 2 ] );
const ddy = this.emitExpression( node.params[ 3 ] );
code = `${wgslFn}(${textureName}, ${samplerName}, ${uv}, ${ddx}, ${ddy})`;
break;
case 'texelFetch':
// format: textureLoad(texture, coords, [level])
const coords = this.emitExpression( node.params[ 1 ] ); // should be ivec
const lodFetch = node.params.length > 2 ? this.emitExpression( node.params[ 2 ] ) : '0';
code = `${wgslFn}(${textureName}, ${coords}, ${lodFetch})`;
break;
default:
code = `/* unsupported texture op: ${node.name} */`;
}
return code;
}
emitBody( body ) {
let code = '';
this.tab += '\t';
for ( const statement of body ) {
code += this.emitExtraLine( statement, body );
if ( statement.isComment ) {
code += this.emitComment( statement, body );
continue;
}
const statementCode = this.emitExpression( statement );
if ( statementCode ) {
code += this.tab + statementCode;
if ( ! statementCode.endsWith( '}' ) && ! statementCode.endsWith( '{' ) ) {
code += ';';
}
code += '\n';
}
}
this.tab = this.tab.slice( 0, - 1 );
return code.slice( 0, - 1 ); // remove the last extra line
}
emitConditional( node ) {
const condStr = this.emitExpression( node.cond );
const bodyStr = this.emitBody( node.body );
let ifStr = `if ( ${ condStr } ) {\n\n${ bodyStr }\n\n${ this.tab }}`;
let current = node;
while ( current.elseConditional ) {
current = current.elseConditional;
const elseBodyStr = this.emitBody( current.body );
if ( current.cond ) { // This is an 'else if'
const elseCondStr = this.emitExpression( current.cond );
ifStr += ` else if ( ${ elseCondStr } ) {\n\n${ elseBodyStr }\n\n${ this.tab }}`;
} else { // This is an 'else'
ifStr += ` else {\n\n${ elseBodyStr }\n\n${ this.tab }}`;
}
}
return ifStr;
}
emitFor( node ) {
const init = this.emitExpression( node.initialization );
const cond = this.emitExpression( node.condition );
const after = this.emitExpression( node.afterthought );
const body = this.emitBody( node.body );
return `for ( ${ init }; ${ cond }; ${ after } ) {\n\n${ body }\n\n${ this.tab }}`;
}
emitWhile( node ) {
const cond = this.emitExpression( node.condition );
const body = this.emitBody( node.body );
return `while ( ${ cond } ) {\n\n${ body }\n\n${ this.tab }}`;
}
emitSwitch( node ) {
const discriminant = this.emitExpression( node.discriminant );
let switchStr = `switch ( ${ discriminant } ) {\n\n`;
this.tab += '\t';
for ( const switchCase of node.cases ) {
const body = this.emitBody( switchCase.body );
if ( switchCase.isDefault ) {
switchStr += `${ this.tab }default: {\n\n${ body }\n\n${ this.tab }}\n\n`;
} else {
const cases = switchCase.conditions.map( c => this.emitExpression( c ) ).join( ', ' );
switchStr += `${ this.tab }case ${ cases }: {\n\n${ body }\n\n${ this.tab }}\n\n`;
}
}
this.tab = this.tab.slice( 0, - 1 );
switchStr += `${this.tab}}`;
return switchStr;
}
emitVariables( node ) {
const declarations = [];
let current = node;
while ( current ) {
const type = this.getWgslType( current.type );
let valueStr = '';
if ( current.value ) {
valueStr = ` = ${this.emitExpression( current.value )}`;
}
// The AST linker tracks if a variable is ever reassigned.
// If so, use 'var'; otherwise, use 'let'.
let keyword;
if ( current.linker ) {
if ( current.linker.assignments.length > 0 ) {
keyword = 'var'; // Reassigned variable
} else {
if ( current.value && current.value.isNumericExpression ) {
keyword = 'const'; // Immutable numeric expression
} else {
keyword = 'let'; // Immutable variable
}
}
}
declarations.push( `${ keyword } ${ current.name }: ${ type }${ valueStr }` );
current = current.next;
}
// In WGSL, multiple declarations in one line are not supported, so join with semicolons.
return declarations.join( ';\n' + this.tab );
}
emitFunction( node ) {
const name = node.name;
const returnType = this.getWgslType( node.type );
const params = [];
// We will prepend to a copy of the body, not the original AST node.
const body = [ ...node.body ];
for ( const param of node.params ) {
const paramName = param.name;
let paramType = this.getWgslType( param.type );
// Handle 'inout' and 'out' qualifiers using pointers. They are already mutable.
if ( param.qualifier === 'inout' || param.qualifier === 'out' ) {
paramType = `ptr<function, ${paramType}>`;
params.push( `${paramName}: ${paramType}` );
continue;
}
// If the parameter is reassigned within the function, we need to
// create a local, mutable variable that shadows the parameter's name.
if ( param.linker && param.linker.assignments.length > 0 ) {
// 1. Rename the incoming parameter to avoid name collision.
const immutableParamName = `${paramName}_in`;
params.push( `${immutableParamName}: ${paramType}` );
// 2. Create a new Accessor node for the renamed immutable parameter.
const immutableAccessor = new Accessor( immutableParamName );
immutableAccessor.isAccessor = true;
immutableAccessor.property = immutableParamName;
// 3. Create a new VariableDeclaration node for the mutable local variable.
// This new variable will have the original parameter's name.
const mutableVar = new VariableDeclaration( param.type, param.name, immutableAccessor );
// 4. Mark this new variable as mutable so `emitVariables` uses `var`.
mutableVar.linker = { assignments: [ true ] };
// 5. Prepend this new declaration to the function's body.
body.unshift( mutableVar );
} else {
// This parameter is not reassigned, so treat it as a normal immutable parameter.
params.push( `${paramName}: ${paramType}` );
}
}
const paramsStr = params.length > 0 ? ' ' + params.join( ', ' ) + ' ' : '';
const returnStr = ( returnType && returnType !== 'void' ) ? ` -> ${returnType}` : '';
// Emit the function body, which now includes our injected variable declarations.
const bodyStr = this.emitBody( body );
return `fn ${name}(${paramsStr})${returnStr} {\n\n${bodyStr}\n\n${this.tab}}`;
}
emitComment( statement, body ) {
const index = body.indexOf( statement );
const previous = body[ index - 1 ];
const next = body[ index + 1 ];
let output = '';
if ( previous && isExpression( previous ) ) {
output += '\n';
}
output += this.tab + statement.comment.replace( /\n/g, '\n' + this.tab ) + '\n';
if ( next && isExpression( next ) ) {
output += '\n';
}
return output;
}
emitExtraLine( statement, body ) {
const index = body.indexOf( statement );
const previous = body[ index - 1 ];
if ( previous === undefined ) return '';
if ( statement.isReturn ) return '\n';
const lastExp = isExpression( previous );
const currExp = isExpression( statement );
if ( lastExp !== currExp || ( ! lastExp && ! currExp ) ) return '\n';
return '';
}
emit( ast ) {
const header = '// Three.js Transpiler r' + REVISION + '\n\n';
let globals = '';
let functions = '';
let dependencies = '';
// 1. Pre-process to find all global declarations
for ( const statement of ast.body ) {
if ( statement.isFunctionDeclaration ) {
this.functions.set( statement.name, statement );
} else if ( statement.isUniform ) {
this.uniforms.push( statement );
} else if ( statement.isVarying ) {
this.varyings.push( statement );
}
}
// 2. Build resource bindings (uniforms, textures, samplers)
if ( this.uniforms.length > 0 ) {
let bindingIndex = 0;
const uniformStructMembers = [];
const textureGlobals = [];
for ( const uniform of this.uniforms ) {
// Textures are declared as separate global variables, not in the UBO
if ( uniform.type.includes( 'texture' ) ) {
textureGlobals.push( ` var ${uniform.name}: ${this.getWgslType( uniform.type )};` );
textureGlobals.push( ` var ${uniform.name}_sampler: sampler;` );
} else {
uniformStructMembers.push( `\t${uniform.name}: ${this.getWgslType( uniform.type )},` );
}
}
// Create a UBO struct if there are any non-texture uniforms
if ( uniformStructMembers.length > 0 ) {
globals += 'struct Uniforms {\n';
globals += uniformStructMembers.join( '\n' );
globals += '\n};\n';
globals += ` var<uniform> uniforms: Uniforms;\n\n`;
}
// Add the texture and sampler globals
globals += textureGlobals.join( '\n' ) + '\n\n';
}
// 3. Build varying structs for stage I/O
// This is a simplification; a full implementation would need to know the shader stage.
if ( this.varyings.length > 0 ) {
globals += 'struct Varyings {\n';
let location = 0;
for ( const varying of this.varyings ) {
globals += `\t@location(${location ++}) ${varying.name}: ${this.getWgslType( varying.type )},\n`;
}
globals += '};\n\n';
}
// 4. Emit all functions and other global statements
for ( const statement of ast.body ) {
functions += this.emitExtraLine( statement, ast.body );
if ( statement.isFunctionDeclaration ) {
functions += this.emitFunction( statement ) + '\n';
} else if ( statement.isComment ) {
functions += this.emitComment( statement, ast.body );
} else if ( ! statement.isUniform && ! statement.isVarying ) {
// Handle other top-level statements like 'const'
functions += this.emitExpression( statement ) + ';\n';
}
}
// 4. Build dependencies
for ( const value of this.polyfills.values() ) {
dependencies = `${ value }\n\n`;
}
return header + dependencies + globals + functions.trimEnd() + '\n';
}
}
export default WGSLEncoder;