rtx: make soft shadows by random sampling dlight surface

it includes bad random function, bad sampling strategy, bad performance,
etc

but it works somewhat

ref_vk/TODO.md

@@ -1,16 +1,18 @@
 ## 2021-03-10
 - [x] rtx: dlights
 - [x] rtx: dlight shadows
+- [x] rtx: dlight soft shadows
 
 # Next
-- [ ] rtx: dlight soft shadows
+- [ ] rtx: model matrices
+- [ ] rtx: blend normals according to barycentrics
 - [ ] rtx: path tracing
 - [ ] rtx: textures
-- [ ] rtx: blend normals according to barycentrics
 - [ ] rtx: light entities
 - [ ] rtx: add fps
 	- [ ] better AS structure (fewer blases, etc)
 	- [ ] rasterize into G-buffer, and only then compute lighting with rtx
+- [ ] rtx: better random
 
 # Planned
 - [ ] restore render debug labels

ref_vk/shaders/rtx.comp

@@ -2,7 +2,6 @@
 #extension GL_EXT_ray_query : require
 #extension GL_EXT_shader_16bit_storage : require
 
-
 // FIXME shader specialization
 layout(local_size_x = 16, local_size_y = 8, local_size_z = 1) in;
 
@@ -38,7 +37,7 @@ struct Light {
 	vec4 color;
 };
 // FIXME what should this be?
-const float dlight_attenuation_const = 5000.;
+const float dlight_attenuation_const = 20000.;
 // TODO specialize in vk_rtx.c
 layout (constant_id = 1) const uint max_dlights = 32;
 layout(set=0,binding=6) uniform UBODLights {
@@ -46,6 +45,16 @@ layout(set=0,binding=6) uniform UBODLights {
 	Light lights[max_dlights];
 };
 
+// TODO find better random function
+float rand01_state;
+float rand01() {
+	return rand01_state = fract(sin(rand01_state)*54873.35729);
+}
+
+layout (push_constant) uniform PC {
+	float t;
+} pc;
+
 void main() {
 	vec2 res = imageSize(image);
 	vec2 uv = (gl_GlobalInvocationID.xy + .5) / res * 2. - 1.;
@@ -66,7 +75,6 @@ void main() {
 		C = vec3(1., 0., 1.);
 	} else {
 		vec3 pos = O+D*l;
-		//C = fract(pos/100.);
 
 		//const int instance_index = rayQueryGetIntersectionInstanceIdEXT(rayQuery, true);
 		const int instance_index = rayQueryGetIntersectionInstanceCustomIndexEXT(rayQuery, true);
@@ -94,10 +102,21 @@ void main() {
 		/* C.b = float((first_vertex_index >> 10) & 31) / 31.f; */
 
 		const vec3 baseColor = vec3(1.);
+		rand01_state = fract((pos.x + pos.y + pos.z)/100.) + uv.x + uv.y + pc.t;
 		for (uint i = 0; i < num_lights; ++i) {
 			const vec4 light_pos_r = lights[i].pos_r;
 			const vec3 light_color = lights[i].color.rgb;
-			const vec3 light_dir = light_pos_r.xyz - pos;
+
+			rand01_state += fract((light_pos_r.x + light_pos_r.y + light_pos_r.z)/100.);
+
+			// Find random point on a sphere
+			// TODO proper BRDF importance sampling and correct random point distribution
+			vec3 rnd = normalize(vec3(rand01()*2.-1., rand01()*2.-1., rand01()*2.-1.));
+			if (dot(rnd, pos - light_pos_r.xyz) < 0.) rnd = -rnd;
+
+			// TODO fudge this
+			const float light_r_scaler = 10.;
+			const vec3 light_dir = light_pos_r.xyz - pos + rnd * light_pos_r.w / light_r_scaler;
 			const vec3 light_dir_norm = normalize(light_dir);
 			const float dot_ld_norm = dot(light_dir_norm, normal);
 			if (dot_ld_norm <= 0.)
@@ -116,6 +135,7 @@ void main() {
 				continue;
 
 			const float r2 = light_pos_r.w * light_pos_r.w;
+			// TODO this is a bad approximation
 			const float attenuation = dlight_attenuation_const / (d2 + r2 * .5);
 			C += baseColor.rgb * light_color * dot_ld_norm * attenuation;
 		}

ref_vk/vk_rtx.c

@@ -422,7 +422,10 @@ void VK_RaySceneEnd(const vk_ray_scene_render_args_t* args)
 
 	// 4. dispatch compute
 	vkCmdBindPipeline(cmdbuf, VK_PIPELINE_BIND_POINT_COMPUTE, g_rtx.pipeline);
-	//vkCmdPushConstants(cmdbuf, g_rtx.pipeline_layout, VK_SHADER_STAGE_COMPUTE_BIT, 0, sizeof(matrix4x4), mvp);
+	{
+		const float t = gpGlobals->realtime;
+		vkCmdPushConstants(cmdbuf, g_rtx.pipeline_layout, VK_SHADER_STAGE_COMPUTE_BIT, 0, sizeof(float), &t);
+	}
 	vkCmdBindDescriptorSets(cmdbuf, VK_PIPELINE_BIND_POINT_COMPUTE, g_rtx.pipeline_layout, 0, 1, &g_rtx.desc_set, 0, NULL);
 	vkCmdDispatch(cmdbuf, (args->dst.width+WG_W-1)/WG_W, (args->dst.height+WG_H-1)/WG_H, 1);
 }
@@ -470,18 +473,18 @@ static void createLayouts( void ) {
 
 	XVK_CHECK(vkCreateDescriptorSetLayout(vk_core.device, &dslci, NULL, &g_rtx.desc_layout));
 
-	/* VkPushConstantRange push_const = {0}; */
-	/* push_const.offset = 0; */
-	/* push_const.size = sizeof(matrix4x4); */
-	/* push_const.stageFlags = VK_SHADER_STAGE_COMPUTE_BIT; */
+	VkPushConstantRange push_const = {0};
+	push_const.offset = 0;
+	push_const.size = sizeof(float);
+	push_const.stageFlags = VK_SHADER_STAGE_COMPUTE_BIT;
 
 	{
 		VkPipelineLayoutCreateInfo plci = {0};
 		plci.sType = VK_STRUCTURE_TYPE_PIPELINE_LAYOUT_CREATE_INFO;
 		plci.setLayoutCount = 1;
 		plci.pSetLayouts = &g_rtx.desc_layout;
-		//plci.pushConstantRangeCount = 1;
-		//plci.pPushConstantRanges = &push_const;
+		plci.pushConstantRangeCount = 1;
+		plci.pPushConstantRanges = &push_const;
 		XVK_CHECK(vkCreatePipelineLayout(vk_core.device, &plci, NULL, &g_rtx.pipeline_layout));
 	}