TSL: if, elseif, else syntax

[sunag]

Description

This PR implements If/Else for TSL (Three.js Shading Language) and Nodes.

TSL: Simple

material.colorNode = new ShaderNode( ( stack ) => {

    const n = temp( 1 );

    stack.if( n.greaterThan( .5 ), ( stack ) => {

        stack.assign( n, .5 );

    } ).else( ( stack ) => {
        
        stack.assign( n, 0 );
        
    } );
    
    return n;

} );

TSL: Complex

material.colorNode = new ShaderNode( ( stack ) => {

    const n = temp( 1 );

    stack.if( n.greaterThan( .5 ), ( stack ) => {

        stack.assign( n, .5 );
        
        stack.if( n.greaterThan( .1 ), ( stack ) => {

            stack.assign( n, .1 );

        } );

    } ).elseif( n.greaterThan( .3 ), ( stack ) => {
        
        stack.assign( n, .3 );
        
    } ).else( ( stack ) => {
        
        stack.assign( n, 0 );
        
    } );
    
    return n;

} );

WGSL: Output example

nodeVar1 = 1.0;

if ( ( nodeVar1 > 0.5 ) ) {

    nodeVar1 = 0.5;

    if ( ( nodeVar1 > 0.1 ) ) {

        nodeVar1 = 0.1;
        

    }

    

} else {


    if ( ( nodeVar1 > 0.3 ) ) {

        nodeVar1 = 0.3;
        

    } else {

        nodeVar1 = 0.0;
        

    }

    

}

[LeviPesin]

Shouldn't we then change usages of new ShaderNode (for example, in Skinning) to shader?

[sunag]

Shouldn't we then change usages of new ShaderNode (for example, in Skinning) to shader?

I think so.

[LeviPesin]

So nice!!!

Now the only major syntax thing remaining to be required in TSL is loops 😃