Vulkan Ray Tracing - Not every primitive Id from any hit shader - c

Question

EDIT: I added the .cpp file of my project, it is quit similar to the example in the repo from Sascha Willems.
I'm new in Vulkan and I try to write a Ray/Triangle intersection. Sadly I did not find an Example. Maybe you know one?
I need these intersections to calculate the attenuation of rays.
So I did a raygen shader like this:
#version 460
#extension GL_NV_ray_tracing : require
#define debug 0
layout(binding = 0, set = 0) uniform accelerationStructureNV topLevelAS;
layout(binding = 1, set = 0, rgba8) uniform image2D image;
layout(binding = 2, set = 0) uniform CameraProperties
{
mat4 viewInverse;
mat4 projInverse;
} cam;
layout(binding = 3, set = 0) buffer detectorProperties
{
double detectorValue[];
} detectors;
//layout(binding = 4, set = 0) buffer outputProperties
//{
// double outputValues[];
//} outputData;
layout(binding = 5, set = 0) buffer debugProperties
{
double debugValues[];
} debugData;
struct RayPayload {
uint outputId;
uint hitCounter;
};
layout(location = 0) rayPayloadNV RayPayload rayPayload;
void main()
{
rayPayload.outputId = gl_LaunchIDNV.x * 18+ gl_LaunchIDNV.y * gl_LaunchSizeNV.x * 18;
rayPayload.hitCounter = 0;
vec3 origin = vec3(cam.viewInverse[0].x, cam.viewInverse[1].y, cam.viewInverse[2].z);
uint rayId = uint(gl_LaunchIDNV.x + gl_LaunchSizeNV.x * gl_LaunchIDNV.y);
uint targetXId = rayId;
uint targetYId = rayId + gl_LaunchSizeNV.x * gl_LaunchSizeNV.y;
uint targetZId = rayId + gl_LaunchSizeNV.x * gl_LaunchSizeNV.y *2;
vec3 target = vec3(detectors.detectorValue[targetXId],detectors.detectorValue[targetYId], detectors.detectorValue[targetZId]) ;
vec3 direction = target.xyz-origin.xyz ;
#ifdef debug
uint debugId = rayPayload.outputId;
debugData.debugValues[debugId + 0 ] = gl_LaunchSizeNV.x;
debugData.debugValues[debugId + 1] = gl_LaunchSizeNV.y;
debugData.debugValues[debugId+ 2 ] = gl_LaunchIDNV.x;
debugData.debugValues[debugId+ 3 ] = gl_LaunchIDNV.y;
debugData.debugValues[debugId + 4] = targetXId;
debugData.debugValues[debugId + 5] = targetYId;
debugData.debugValues[debugId + 6] = targetZId;
debugData.debugValues[debugId + 7] = target.x;
debugData.debugValues[debugId + 8] = target.y;
debugData.debugValues[debugId + 9] = target.z;
debugData.debugValues[debugId + 10] = origin.x;
debugData.debugValues[debugId + 11] = origin.y;
debugData.debugValues[debugId + 12] = origin.z;
debugData.debugValues[debugId + 13] = direction.x;
debugData.debugValues[debugId + 14] = direction.y;
debugData.debugValues[debugId + 15] = direction.z;
debugData.debugValues[debugId + 16] = rayId;
debugData.debugValues[debugId + 17] = rayPayload.outputId;
#endif
uint rayFlags = gl_RayFlagsNoneNV;
uint cullMask = 0xff;
float tmin = 0.00001;
float tmax = 10000.0;
traceNV(topLevelAS, rayFlags, cullMask, 0, 0, 0, origin.xyz, tmin, direction.xyz, tmax, 0);
// uint outputId = gl_LaunchIDNV.x * 18+ gl_LaunchIDNV.y * gl_LaunchSizeNV.x *18;
// outputData.outputValues[outputId + hitCounter] = double(hitValue[hitCounter]);
imageStore(image, ivec2(gl_LaunchIDNV.xy), vec4(rayPayload.hitCounter,0,0, 0.0));
}
And with the any-hit shader I just want to give back the primitive Id like that:
#version 460
#extension GL_NV_ray_tracing : require
#extension GL_EXT_nonuniform_qualifier : enable
layout(binding = 4, set = 0) buffer outputProperties
{
float outputValues[];
} outputData;
struct RayPayload {
uint outputId;
uint hitCounter;
};
layout(location = 0) rayPayloadInNV RayPayload rayPayload;
hitAttributeNV vec3 attribs;
void main()
{
// uint outputIdCurrentTriangle = rayPayload.outputId + rayPayload.hitCounter;
uint outputIdCurrentTriangle = rayPayload.outputId + rayPayload.hitCounter++;
outputData.outputValues[outputIdCurrentTriangle] = gl_PrimitiveID;
// rayPayload.hitCounter ++;
}
You can see the .cpp file here:
https://drive.google.com/file/d/1iTX3ATaP3pT7d4CEowo4IVnQxTOerxaD/view?usp=sharing
My Problem is, that I just find all surface triangles, nearest to the source even though the object is noOpaque (it's tested with setting Rayflag to cullNoOpaques).
Is anyone have the same problem or have an example which also gives primitivesId of any hit back?
I just found one Example for any-hit shaders. Is the any-hit shader this less used?
Thank you for your help!

Answer 1

If you want to have your any hit shader to register intersections for all triangles in your scene you should call ignoreIntersectionNV in your any hit shader (see GLSL_NV_ray_tracing specs).
With this, your any hit shader will carry on without modifying gl_RayTmaxNV and gl_HitKindNV, triggering for all ray intersections.
With a simple any hit shader like this:
#version 460
#extension GL_NV_ray_tracing : require
#extension GL_GOOGLE_include_directive : enable
#include "raypayload.glsl"
layout(binding = 1, set = 0, rgba8) uniform image2D image;
layout(location = 0) rayPayloadInNV RayPayload rayPayload;
void main()
{
rayPayload.hitcount++;
ignoreIntersectionNV();
}
The hitCount will be increased by one for each intersection, visualizing this with color coding by hitcount will yield something like this: