SCNProgram not affecting SCNFloor - swift

Question

In my experiments using the shader modifier, I saw that the array data could not be transferred to the shader.
Scenekit giving buffer size error while passing array data to uniform array in openGL shader
For this reason I decided to try SCNProgram. But now I realize that the shaders I added using SCNProgram do not work on SCNFloor.
Is there a particular reason for this problem?
Super simple shaders which I use for testing;
vertex shader
precision highp float;
attribute vec3 vertex;
uniform mat4 ModelViewProjectionMatrix;
void main()
{
gl_Position = ModelViewProjectionMatrix * vec4(vertex, 1.0);
}
fragment shader
precision mediump float;
void main( void )
{
gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);
}

Answer 1

You can try to make your own vert and frag shaders to kinda do the same thing. I've done a similar thing with webgl / glsl es2, or just paint it solid, tint the existing floor:
uniform mat4 uCameraWM; //camera world matrix
uniform vec2 uCamAspFov; //x:aspect ratio y:tan(fov/2)
varying vec3 vVDw; //view direction
void main(){
//construct frustum, scale and transform a unit quad
vec4 viewDirWorld = vec4(
position.x * uCamAspFov.x,
position.y,
-uCamAspFov.y, //move it to where 1:aspect fits
0.
);
vVDw = ( uCameraWM * viewDirWorld ).xyz; //transform to world
gl_Position = vec4( position.xy , 0. , 1. ); //draw a full screen quad
}
Frag:
(ignore the cruft, point is to intersect the view direction ray with a plane, map it, you can look up a cubemap in the sky portion instead of discarding it)
uniform float uHeight;
uniform sampler2D uTexDiff;
uniform sampler2D uTexNorm;
uniform sampler2D uTexMask;
varying vec2 vUv;
varying vec3 vVDw;
struct Plane
{
vec3 point;
vec3 normal;
float d;
};
bool rpi( in Plane p , in vec3 p0 , in vec3 vd , out vec3 wp )
{
float t;
t = -( dot( p0 , p.normal ) + p.d ) / dot( vd , p.normal );
wp = p0 + t * vd;
return t > 0. ? true : false;
}
void main(){
Plane plane;
plane.point = vec3( 0. , uHeight , 0. );
plane.normal = vec3( 0. , 1. , .0 );
plane.d = -dot( plane.point , plane.normal );
vec3 ld = normalize( vec3(1.,1.,1.) );
vec3 norm = plane.normal;
float ndl = dot( norm , ld ) ;
vec2 uv;
vec3 wp;
vec3 viewDir = normalize( vVDw );
vec3 h = normalize((-viewDir + ld));
float spec = clamp( dot( h , norm ) , .0 , 1. );
// spec = pow( spec , 5. );
if( dot(plane.normal , cameraPosition) < 0. ) discard;
if( !rpi( plane , cameraPosition , viewDir , wp ) ) discard;
uv = wp.xz;
vec2 uvm = uv * .0105;
vec2 uvt = uv * .2;
vec4 tmask = texture2D( uTexMask , uvm );
vec2 ch2Scale = vec2(1.8,1.8);
vec2 ch2Scale2 = vec2(1.6,1.6);
vec2 t1 = uvt * ch2Scale2 - vec2(tmask.z , -tmask.z) ;
// vec2 t2 = uvt * ch2Scale + tmask.z ;
// vec2 t3 = uvt + vec2(0. , mask.z-.5) * 1.52;
vec3 diffLevels = ( texture2D( uTexDiff , t1 ) ).xyz;
// vec3 diffuse2 = ( texture2D( uTexDiff, fract(t1) * vec2(.5,1.) + vec2(.5,.0) ) ).xyz;
// vec3 diffuse1 = ( texture2D( uTexDiff, fract(t2) * vec2(.5,1.) ) ).xyz;
// vec4 normalMap2 = texture2D( uTexNorm, fract(t1) * vec2(.5,1.) + vec2(.5,.0) );
// vec4 normalMap1 = texture2D( uTexNorm, fract(t2) * vec2(.5,1.) );
float diffLevel = mix(diffLevels.y, diffLevels.x, tmask.x);
diffLevel = mix( diffLevel , diffLevels.z, tmask.y );
// vec3 normalMix = mix(normalMap1.xyz, normalMap2.xyz, tmask.x);
// vec2 g = fract(uv*.1) - .5;
// float e = .1;
// g = -abs( g ) + e;
float fog = distance( wp.xz , cameraPosition.xz );
// float r = max( smoothstep( 0.,e,g.x) , smoothstep( 0.,e,g.y) );
gl_FragColor.w = 1.;
gl_FragColor.xyz = vec3(tmask.xxx);
gl_FragColor.xyz = vec3(diffLevel) * ndl + spec * .5;
}
But overall, the better advice would be just to give up on scenekit and save yourself a TON of frustration.

Answer 2

Finally Apple Developer Technical Support answered the question I asked about this issue.
Here is the answer that they give.
Unfortunately, there is not a way to shade floor as such. The
SceneKit team admits that SCNFloor is a different kind of object that
is not intended for use with SCNProgram. Furthermore, using the
.fragment shader entry point does not work either (such as:)
func setFragmentEntryPoint( _ node: SCNNode ) {
print( #function + " setting fragment entry point for \(node)" )
DispatchQueue.main.asyncAfter( deadline: DispatchTime.now() + DispatchTimeInterval.milliseconds( 2500 ) ) {
let geometry = node.geometry!
let dict: [SCNShaderModifierEntryPoint:String] = [.fragment :
"_output.color = vec4( 0.0, 1.0, 0.0, 1.0 );"]
geometry.shaderModifiers = dict
}
}
Though the SceneKit team considered this behavior to be expected, you
may still file a bug report which in this case will be interpreted as
an API enhancement request.