SCNProgram 不影响 SCNFloor

Question

在我使用着色器修改器的实验中，我发现数组数据无法传输到着色器。

Scenekit giving buffer size error while passing array data to uniform array in openGL shader

出于这个原因，我决定尝试 SCNProgram。但是现在我意识到我使用 SCNProgram 添加的着色器在 SCNFloor 上不起作用。

这个问题有什么特别的原因吗？

我用于测试的超级简单的着色器；

顶点着色器

precision highp float;
attribute vec3 vertex;
uniform mat4 ModelViewProjectionMatrix;

void main()
{
    gl_Position = ModelViewProjectionMatrix * vec4(vertex, 1.0);
}

片段着色器

precision mediump float;

void main( void )
{   
    gl_FragColor = vec4(0.0, 1.0, 0.0, 1.0);
}

Answer 1

您可以尝试制作自己的垂直和碎片着色器来做同样的事情。我用 webgl / glsl es2 做了类似的事情，或者只是把它涂成实心，给现有的地板着色：

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

}

碎片：（无视cruft，重点是将视线方向光线与平面相交，贴图，可以在天空部分查找立方体贴图而不是丢弃它）

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;

}

但总的来说，更好的建议是放弃 scenekit 并为自己省去一大堆挫折。

Answer 2

Apple Developer Technical Support 终于回答了我关于这个问题的问题。

这是他们给出的答案。

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.

SCNProgram 不影响 SCNFloor

SCNProgram not affecting SCNFloor

shader

glsl

opengl-es-2.0

scenekit

swift