WebGL to DCTL

This article is mainly based on @J-i-P-i's excellent WSL post "Convert a Shadertoy WebGL Code to DCTL" which is the main basis and origin for this whole repository.

Show Stoppers

Before converting a Shadertoy you should have a look if the code contains something yet not possible to convert:

• dFdx / dFdy
• texelfetch

For other challenges there might be workarounds, but you should check the impact on the resulting image beforehand:

• for textureLod omittimg the LOD by using _tex2DVecN might be sufficient
• ...

Porting Vector Types

Replace WebGL's vec2, vec3, vec4 types by DCTL's float2, float3, float4. Note that for r-values you must use the corresponding to_float-functions.

For example ...

vec3 v = vec3(.2,.4,1.3);

... translates to ...

float3 v = to_float3(0.2f,0.4f,1.3f);

One speciality with those vector types ist, that accessing multiple vector elements at ones (e.g. float2 c=coords.xy) must be resolved to single element access (the example could be converted to float2 c = to_float2(coords.x,coords.y)). See swizzling for further details and more examples.

Build-In Math Functions

DCTL provides a lot of substitutes like _sinf(float), _cosf(float) for the common math functions sin(T), cos(T) to avoid ambiguities in particular with single precision, and double precision floating point types, and overloaded functions.

replace	with
sin, cos, pow	_sinf, _cosf, _powf
max, min	_fmaxf, _fminf
abs, mod	_fabs, mod_f (Incompatibility)
atan	_atan2f (possibly on _atan2f (var, 1.0f); expand)
clamp, dot, step	no replacement needed
mix	_mix

See math.h for further details.