vk: rt: add white furnace debug display mode

Known issues:
- it doesn't really look how it's supposed to look
- using debug display mode for it was a mistake

ref/vk/TODO.md

@@ -1,7 +1,14 @@
 ## Next
-- [ ] white furnace test
+- [ ] fix no-hit bounce absent legacy blending
+- [ ] -vkdbgprintf or something
 - [ ] performance profiling and comparison
 
+## 2024-01-26 E369
+- [ ] white furnace test
+	- [x] do it using display_only mode
+	- [ ] do it via separate flag
+
+# Previously
 ## 2024-01-23 E368
 - [ ] specular bounce
     - [x] specular-vs-diffuse choice based on metalness+frensel
@@ -14,7 +21,6 @@
 	- [ ] BRDF material params attenuation
 		- [x] try improving, multiply specular by fresnel
 
-
 ## 2024-01-22 E367
 - [ ] specular bounce
     - [ ] specular-vs-diffuse choice based on metalness+frensel
@@ -25,7 +31,6 @@
 	- [ ] BRDF material params attenuation
 	- [ ] decide on the diffuse-vs-specular out channel based on the first bounce
 
-# Previously
 ## 2024-01-19 E366
 - [x] investigate more shading nans
 	- found zero normals in studio models, see #731

ref/vk/shaders/bounce.comp

@@ -49,6 +49,7 @@ layout(set = 0, binding = 33, std430) readonly buffer Vertices { Vertex a[]; } v
 #include "light.glsl"
 
 #include "trace_simple_blending.glsl"
+#include "skybox.glsl"
 
 void readNormals(ivec2 uv, out vec3 geometry_normal, out vec3 shading_normal) {
 	const vec4 n = imageLoad(normals_gs, uv);
@@ -189,7 +190,8 @@ void computeBounces(MaterialEx mat, vec3 pos, vec3 direction, inout vec3 diffuse
 
 			hit_skybox = payload.hit_t.w < 0.;
 		} else {
-			lighting = texture(skybox, bounce_direction).rgb * ubo.ubo.skybox_exposure;
+			// FIXME this no-hit path should still do traceLegacyBlending()
+			lighting = sampleSkybox(bounce_direction);
 			hit_skybox = true;
 		} // not hit
 

ref/vk/shaders/denoiser.comp

@@ -263,6 +263,7 @@ void main() {
 	const Components c = blurSamples(res, pix);
 
 	if (ubo.ubo.debug_display_only == DEBUG_DISPLAY_DISABLED) {
+		// Skip
 	} else if (ubo.ubo.debug_display_only == DEBUG_DISPLAY_DIRECT) {
 		imageStore(out_dest, pix, vec4(LINEARtoSRGB(c.direct_diffuse + c.direct_specular), 0.)); return;
 		return;

ref/vk/shaders/light.glsl

@@ -192,6 +192,11 @@ void computePointLights(vec3 P, vec3 N, uint cluster_index, vec3 view_dir, Mater
 void computeLighting(vec3 P, vec3 N, vec3 view_dir, MaterialProperties material, out vec3 diffuse, out vec3 specular) {
 	diffuse = specular = vec3(0.);
 
+	// No direct lighting for white furnace mode. The only light sources is no-hit|SURF_SKY bounce indirect light.
+	if (ubo.ubo.debug_display_only == DEBUG_DISPLAY_WHITE_FURNACE) {
+		return;
+	}
+
 #ifdef DEBUG_VALIDATE_EXTRA
 	if (IS_INVALIDV(P) || IS_INVALIDV(N) || IS_INVALIDV(view_dir)) {
 		debugPrintfEXT("INVALID computeLighting(P=(%f,%f,%f), N=(%f,%f,%f), view_dir=(%f,%f,%f))",

ref/vk/shaders/ray_interop.h

@@ -187,6 +187,7 @@ struct LightCluster {
 #define DEBUG_DISPLAY_INDIRECT_SPEC 13
 #define DEBUG_DISPLAY_TRIHASH 14
 #define DEBUG_DISPLAY_MATERIAL 15
+#define DEBUG_DISPLAY_WHITE_FURNACE 16
 // add more when needed
 
 struct UniformBuffer {

ref/vk/shaders/ray_primary.comp

@@ -34,6 +34,7 @@ layout(set = 0, binding = 33, std430) readonly buffer Vertices { Vertex a[]; } v
 #include "ray_primary_hit.glsl"
 
 #include "trace_simple_blending.glsl"
+#include "skybox.glsl"
 
 struct Ray {
 	vec3 origin, direction;
@@ -116,7 +117,7 @@ void main() {
 		L = rayQueryGetIntersectionTEXT(rq, true);
 	} else {
 		// Draw skybox when nothing is hit
-		payload.emissive.rgb = texture(skybox, ray.direction).rgb * ubo.ubo.skybox_exposure;
+		payload.emissive.rgb = sampleSkybox(ray.direction);
 	}
 
 	const vec4 blend = traceLegacyBlending(ray.origin, ray.direction, L);

ref/vk/shaders/ray_primary.rchit

@@ -27,6 +27,7 @@ hitAttributeEXT vec2 bary;
 #include "color_spaces.glsl"
 
 #include "rt_geometry.glsl"
+#include "skybox.glsl"
 
 vec4 sampleTexture(uint tex_index, vec2 uv, vec4 uv_lods) {
 	return textureGrad(textures[nonuniformEXT(tex_index)], uv, uv_lods.xy, uv_lods.zw);
@@ -41,7 +42,7 @@ void main() {
 	const Kusok kusok = getKusok(geom.kusok_index);
 
 	if (kusok.material.tex_base_color == TEX_BASE_SKYBOX) {
-		payload.emissive.rgb = texture(skybox, gl_WorldRayDirectionEXT).rgb * ubo.ubo.skybox_exposure;
+		payload.emissive.rgb = sampleSkybox(gl_WorldRayDirectionEXT);
 		return;
 	} else {
 		const vec4 color = getModelHeader(gl_InstanceID).color * kusok.material.base_color;

ref/vk/shaders/ray_primary_hit.glsl

@@ -8,6 +8,7 @@
 #include "ray_kusochki.glsl"
 #include "rt_geometry.glsl"
 #include "color_spaces.glsl"
+#include "skybox.glsl"
 
 #include "noise.glsl" // for DEBUG_DISPLAY_SURFHASH
 
@@ -32,7 +33,7 @@ void primaryRayHit(rayQueryEXT rq, inout RayPayloadPrimary payload) {
 	if (kusok.material.tex_base_color == TEX_BASE_SKYBOX) {
 		// Mark as non-geometry
 		payload.hit_t.w = -payload.hit_t.w;
-		payload.emissive.rgb = texture(skybox, rayDirection).rgb * ubo.ubo.skybox_exposure;
+		payload.emissive.rgb = sampleSkybox(rayDirection);
 		return;
 	} else {
 		payload.base_color_a = sampleTexture(material.tex_base_color, geom.uv, geom.uv_lods);
@@ -137,6 +138,11 @@ void primaryRayHit(rayQueryEXT rq, inout RayPayloadPrimary payload) {
 
 	if (ubo.ubo.debug_display_only == DEBUG_DISPLAY_DISABLED) {
 		// Nop
+	} else if (ubo.ubo.debug_display_only == DEBUG_DISPLAY_WHITE_FURNACE) {
+		// White furnace mode: everything is diffuse and white
+		payload.base_color_a.rgb = vec3(1.);
+		payload.emissive.rgb = vec3(0.);
+		payload.material_rmxx.rg = vec2(1., 0.);
 	} else if (ubo.ubo.debug_display_only == DEBUG_DISPLAY_SURFHASH) {
 		const uint hash = xxhash32(geom.kusok_index);
 		payload.emissive.rgb = vec3(0xff & (hash>>16), 0xff & (hash>>8), 0xff & hash) / 255.;

ref/vk/shaders/skybox.glsl

@@ -0,0 +1,12 @@
+#ifndef SKYBOX_GLSL_INCLUDED
+#define SKYBOX_GLSL_INCLUDED
+
+vec3 sampleSkybox(vec3 direction) {
+	if (ubo.ubo.debug_display_only != DEBUG_DISPLAY_WHITE_FURNACE) {
+		return texture(skybox, direction).rgb * ubo.ubo.skybox_exposure;
+	} else {
+		return vec3(1.);
+	}
+}
+
+#endif // #ifndef SKYBOX_GLSL_INCLUDED

ref/vk/vk_rtx.c

@@ -168,6 +168,7 @@ static void parseDebugDisplayValue( void ) {
 	X(INDIRECT_SPEC, "indirect specular only") \
 	X(TRIHASH, "each triangle is drawn with random color") \
 	X(MATERIAL, "red = roughness, green = metalness") \
+	X(WHITE_FURNACE, "white furnace mode: diffuse white materials, diffuse sky light only") \
 
 #define X(suffix, info) \
 	if (0 == Q_stricmp(cvalue, #suffix)) { \