TSL: Wrong compilation of `min(...)` and `max(...)` with 3 or more parameters

[boytchev]

Description

TSL allows many parameters to functions min(...) and max(...). Using more than 2 parameters, however, fails:

• Both GLSL and WGSL trigger a syntax error, as they support only two parameters, but the code has 3 parameters
• The compiled code contains only the first three parameters; the rest are silently ignored

The GLSL error is:

THREE.WebGLBackend: Must have a compiled fragment shader attached:
SHADER_INFO_LOG:
ERROR: 0:56: 'min' : no matching overloaded function found
ERROR: 0:56: 'max' : no matching overloaded function found

The WGSL error is (significantly shortened):

Error while parsing WGSL: no matching call to
'min(abstract-float, abstract-float, abstract-float)'
overload expects 2 arguments, call passed 3 arguments

Suggested solutions

• compile min(a,b,c,d,...) into min(a,min(b,min(c,...))); and the same for max
• throw an error message if more than 2 parameters are used
• describe in the documentation what functions accept multiple parameters and how they are dealt with when the functions are chained

Untested situation

Chained min(...) and max(...) are not tested

Reproduction steps

1. Use min or max with more than 3 parameters:

mn = min( 11, 12, 13, 14, 15 );
mx = max( 21, 22, 23, 24, 25 );

2. Observe the error message in the console

Code

(see the live example)

Live example

Minimal code. Does not render anything meaningful, just generates the error messages.

https://codepen.io/boytchev/pen/RwmyQLY

Screenshots

Demonstration that only the first three parameters are compiled:

Using the TSL editor in GLSL mode:

Using the TSL editor in WGSL mode:

Version

r165

Device

Desktop

Browser

Chrome, Firefox

OS

Windows