Seele/res/shaders/raytracing/ClosestHit.slang

import Common;
import MaterialParameter;
import LightEnv;
import VertexData;
import Material;
import StaticMeshVertexData;
import MATERIAL_FILE_NAME;
import RayTracingData;
import Scene;

// simplification: all BLAS only have 1 geometry

/*vec3 nextEventEstimation(vec3 accmat, vec3 w, vec3 x, vec3 nl, float kt, bool useAtt, vec3 rnd) {
            uint triId = 0;
            uint sphereId = 0;
            ShadingParams paramsls;
            Material matls;
            vec3 result = vec3(0);
            // Direct Illumination: Next Event Estimation over any present lights
            for (int i = spheres.length(); i-->0;) {
                Sphere ls = spheres[i];
                if (all(equal(ls.e, vec3(0)))) continue; // skip non-emissive spheres
                vec3 xc = ls.geo.xyz - x;
                vec3 sw = normalize(xc), su = normalize(cross((abs(sw.x)>.1 ? vec3(0,1,0) : vec3(1,0,0)), sw)), sv = cross(sw,su);
                float cos_a_max = sqrt(float(1 - ls.geo.w*ls.geo.w / dot(xc,xc)));
                float cos_a = 1 - rnd.x + rnd.x*cos_a_max, sin_a = sqrt(1 - cos_a*cos_a);
                float phi = 2 * pi * rnd.y;
                vec3 l = normalize(su*cos(phi)*sin_a + sv*sin(phi)*sin_a + sw*cos_a);   // sampled direction towards light
                if (intersect(Ray(x,l), matls, paramsls, sphereId, triId) && sphereId == i) {      // test if shadow ray hits this light
   source float omega = 2 * pi * (1-cos_a_max); if(useAtt) { float tau = exp(-kt * length(x - paramsls.x)); result += max(dot(l,nl),0) *
   ls.e * omega * tau; } else { result += accmat / pi * max(dot(l,nl),0) * ls.e * omega;   // brdf term obj.c.xyz already in accmat, 1/pi
   for brdf
                    }
                }
            }
            for(int i = meshLights.length(); i-->0;) {
                MeshDescriptor mesh = meshes[meshLights[i]];
                for(int j = 0; j < mesh.numIndices; j+=3) {
                    vec3 A = vec3(vertices[mesh.vertexOffset + indices[mesh.indexOffset + j + 0]]);
                    vec3 B = vec3(vertices[mesh.vertexOffset + indices[mesh.indexOffset + j + 1]]);
                    vec3 C = vec3(vertices[mesh.vertexOffset + indices[mesh.indexOffset + j + 2]]);
                    float b1 = 1 - sqrt(rnd.x);
                    float b2 = (1 - rnd.y) * sqrt(rnd.x);
                    float b3 = rnd.y * sqrt(rnd.x);
                    vec3 P = A * b1 + B * b2 + C * b3;
                    vec3 omega = P - x;
                    vec3 l = normalize(omega);
                    float v = 0.f;
                    if(intersect(Ray(x,l), matls, paramsls, sphereId, triId) && triId == j) {
                        v = 1.0f;
                    }
                    vec3 e1 = C - A;
                    vec3 e2 = B - A;
                    float area = length(cross(e1, e2)) / 2;
                    float rayLen = length(omega);
                    float cosTheta = dot(nl, l);
                    float cosThetaDash = dot(paramsls.n, -l);
                    float factor = area * (cosThetaDash / (rayLen * rayLen));
                    if(useAtt) {
                        float tau = phase(w, l) * exp(-kt * length(x - paramsls.x));
                        result += tau * matls.e * max(cosTheta, 0) * factor;
                    } else {
                        result += accmat * (matls.e * max(cosTheta, 0) * factor) / pi;
                    }
                }
            }
            return result;
        }

*/

const static float ka = 0;
const static float ks = 0;
const static float3 fogEmm = float3(0, 0.01, 0.01);

const static float eps = 1e-5;
[shader("closesthit")]
void closestHit(inout RayPayload hitValue, in BuiltInTriangleIntersectionAttributes attr) {
    hitValue.hit = true;
    // todo: replace with anyhit shader
    if (hitValue.anyHit)
        return;

    const float3 barycentricCoords = float3(1.0f - attr.barycentrics.x - attr.barycentrics.y, attr.barycentrics.x, attr.barycentrics.y);

    InstanceData inst = pScene.instances[InstanceID()];
    MeshData m = pScene.meshData[InstanceID()];

    // offset into the index buffer
    uint indexOffset = m.indicesRange.offset;
    // added to indices to reference correct part of global mesh pool
    uint vertexOffset = pScene.meshletInfos[m.meshletRange.offset].indicesOffset;

    uint vertexIndex0 = vertexOffset + pRayTracingParams.indexBuffer[indexOffset + 3 * PrimitiveIndex() + 0];
    uint vertexIndex1 = vertexOffset + pRayTracingParams.indexBuffer[indexOffset + 3 * PrimitiveIndex() + 1];
    uint vertexIndex2 = vertexOffset + pRayTracingParams.indexBuffer[indexOffset + 3 * PrimitiveIndex() + 2];

    VertexAttributes attr0 = pVertexData.getAttributes(vertexIndex0);
    VertexAttributes attr1 = pVertexData.getAttributes(vertexIndex1);
    VertexAttributes attr2 = pVertexData.getAttributes(vertexIndex2);

    FragmentParameter f0 = attr0.getParameter(inst.transformMatrix, inst.inverseTransformMatrix);
    FragmentParameter f1 = attr1.getParameter(inst.transformMatrix, inst.inverseTransformMatrix);
    FragmentParameter f2 = attr2.getParameter(inst.transformMatrix, inst.inverseTransformMatrix);

    FragmentParameter params = FragmentParameter.interpolate(f0, f1, f2, barycentricCoords);

    hitValue.params = params.getLightingParameter();
    hitValue.materialParams = params.getMaterialParameter();

    LightingParameter lightingParams = hitValue.params;
    lightingParams.viewDir_WS = -WorldRayDirection();
    let brdf = Material.prepare(hitValue.materialParams);

    float3 normal_WS = brdf.getNormal();
    float3 normalLight_WS = dot(normal_WS, WorldRayDirection()) < 0 ? normal_WS : -normal_WS;
    float3 intersection_WS = lightingParams.position_WS;

    hitValue.depth++;
    float3 rnd = rand01(hitValue.rndSeed);
    // float kt = ka + ks;
    // float s = -log(rnd.z) / kt;
    // if (s < RayTCurrent()) {
    //	float3 xs = WorldRayOrigin() + s * WorldRayDirection();
    //     float p = kt * rnd.z;
    //     if (hitValue.depth > 5) {
    //         if (rnd.z >= p) return;
    //         else brdf.baseColor /= p;
    //     }
    //     float3 ldirect = nextEventEstimation(brdf.baseColor, WorldRayDirection(), xs, -WorldRayDirection(), kt, true, rnd);
    //     hitValue.light += (fogEmm + ks * ldirect) / kt;
    //     accmat *= ks / kt;
    //     rayDesc.Origin = xs;
    //     rayDesc.Direction = float3(
    //         cos(2*PI*rnd.x)*sqrt(1-rnd.y*rnd.y),
    //         sin(2*PI*rnd.x)*sqrt(1-rnd.y*rnd.y),
    //         rnd.y
    //     );
    //     TraceRay(scene, 0, 0xff, 0, 0, rayDesc);
    // }

    float p = max(max(brdf.getBaseColor().x, brdf.getBaseColor().y), brdf.getBaseColor().z);
    if (hitValue.depth > 5) {
        if (rnd.z >= p)
            return;
    }

    hitValue.light += brdf.getEmissive() * hitValue.emissive + brdf.evaluateAmbient(lightingParams.viewDir_WS);
    //-- Ideal DIFFUSE reflection
    // if(bool(useNEE)) {
    //    accrad += nextEventEstimation(accmat, r.d, params.x, params.nl, kt, false, rnd);
    //}
    // Only trace shadow rays for direct lighting at shallow depths
    if (hitValue.depth <= 3) {
        for (uint i = 0; i < pLightEnv.numDirectionalLights; ++i) {
            float3 x = intersection_WS;
            float3 l = -pLightEnv.directionalLights[i].direction.xyz;
            RayDesc rayDesc;
            rayDesc.TMax = 10000.0f;
            rayDesc.TMin = eps;
            rayDesc.Origin = x;
            rayDesc.Direction = l;
            RayPayload payload;
            payload.depth = hitValue.depth;
            payload.emissive = 1;
            payload.anyHit = true;
            payload.hit = false;
            payload.rndSeed = hitValue.rndSeed;
            TraceRay(pRayTracingParams.scene, RAY_FLAG_CULL_BACK_FACING_TRIANGLES | RAY_FLAG_ACCEPT_FIRST_HIT_AND_END_SEARCH, 0xff, 0, 0, 0,
                     rayDesc, payload);

            // we have missed all geometry, so directional light is affecting us
            if (!payload.hit) {
                hitValue.light += pLightEnv.directionalLights[i].illuminate(lightingParams, brdf);
            }
        }
        for (uint i = 0; i < pLightEnv.numPointLights; ++i) {
            RayPayload payload;
            payload.rndSeed = hitValue.rndSeed;
            float3 x = intersection_WS;
            float3 l = pLightEnv.pointLights[i].position_WS.xyz - intersection_WS;
            if (length(l) > pLightEnv.pointLights[i].colorRange.w) {
                continue;
            }
            RayDesc rayDesc;
            rayDesc.TMax = 1.0f;
            rayDesc.TMin = eps;
            rayDesc.Origin = x;
            rayDesc.Direction = l;
            TraceRay(pRayTracingParams.scene, RAY_FLAG_CULL_BACK_FACING_TRIANGLES | RAY_FLAG_ACCEPT_FIRST_HIT_AND_END_SEARCH, 0xff, 0, 0, 0,
                     rayDesc, payload);

            // hitting only after the light
            if (!payload.hit) {
                hitValue.light += pLightEnv.pointLights[i].illuminate(lightingParams, brdf);
            }
        }
    } // end depth <= 2 direct lighting guard
    // Indirect Illumination: probabilistic diffuse/specular importance sampling
    if (hitValue.depth < 3) {
        float3 V = -WorldRayDirection();
        float3 N = normalLight_WS;
        float rough = brdf.getRoughness();
        float met = brdf.getMetallic();
        float3 F0 = lerp(float3(0.04), brdf.getBaseColor(), met);
        float NdotV = max(dot(N, V), 0.001);
        float3 F = F0 + (1 - F0) * pow(1 - NdotV, 5.0);
        float specProb = clamp((F.x + F.y + F.z) / 3.0, 0.1, 0.9);

        RayDesc rayDesc;
        rayDesc.TMax = 10000.0f;
        rayDesc.TMin = eps;
        rayDesc.Origin = intersection_WS;

        float3 bounceWeight = float3(0);
        bool validBounce = true;

        if (rnd.z < specProb) {
            // GGX importance sampling for specular reflection
            float a = max(rough * rough, 0.001);
            float a2 = a * a;
            float phi = 2.0 * PI * rnd.x;
            float cosTheta = sqrt((1.0 - rnd.y) / (1.0 + (a2 - 1.0) * rnd.y));
            float sinTheta = sqrt(1.0 - cosTheta * cosTheta);

            float3 u = normalize(cross(abs(N.x) > 0.1 ? float3(0, 1, 0) : float3(1, 0, 0), N));
            float3 v = cross(N, u);
            float3 H = normalize(u * cos(phi) * sinTheta + v * sin(phi) * sinTheta + N * cosTheta);
            float3 L = reflect(-V, H);
            rayDesc.Direction = L;

            float NdotL = dot(N, L);
            float NdotH = max(dot(N, H), 0.0);
            float VdotH = max(dot(V, H), 0.0);

            if (NdotL <= 0) {
                validBounce = false;
            } else {
                // Smith G term
                float k = (rough + 1);
                k = (k * k) / 8;
                float G = (NdotV / (NdotV * (1 - k) + k)) * (NdotL / (NdotL * (1 - k) + k));
                // Fresnel at half-vector
                float3 Fh = F0 + (max(float3(1.0 - rough), F0) - F0) * pow(clamp(1 - VdotH, 0, 1), 5.0);
                // Monte Carlo weight: F * G * VdotH / (NdotH * NdotV * specProb)
                bounceWeight = Fh * G * VdotH / (NdotH * NdotV * specProb + 0.0001);
            }
        } else {
            // Cosine-weighted importance sampling for diffuse
            float r1 = 2 * PI * rnd.x, r2 = rnd.y, r2s = sqrt(r2);
            float3 w = N;
            float3 u = normalize(cross(abs(w.x) > 0.1 ? float3(0, 1, 0) : float3(1, 0, 0), w));
            float3 v = cross(w, u);
            rayDesc.Direction = normalize(u * cos(r1) * r2s + v * sin(r1) * r2s + w * sqrt(1 - r2));
            // Diffuse weight: kd * baseColor / (1 - specProb)
            float3 kd = (1 - F) * (1 - met);
            bounceWeight = kd * brdf.getBaseColor() / (1 - specProb);
        }

        if (validBounce) {
            RayPayload payload;
            payload.light = float3(0);
            payload.hit = false;
            payload.emissive = 0;
            payload.depth = hitValue.depth;
            payload.anyHit = false;
            payload.rndSeed = hitValue.rndSeed + 1;
            TraceRay(pRayTracingParams.scene, RAY_FLAG_CULL_BACK_FACING_TRIANGLES, 0xff, 0, 0, 0, rayDesc, payload);
            hitValue.light += bounceWeight * payload.light;
        }
    }
    // hitValue.light /= p;
}