From 4e236326c1375d5c52068f7898b1d43b5263e885 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Cl=C3=A9ment=20Foucault?= <foucault.clem@gmail.com>
Date: Mon, 15 Mar 2021 15:32:26 +0100
Subject: EEVEE: Contact Shadow: Fix self intersection issues

This was cause by the change of some epsilon values for reflections.

This commit changes the planar reflection tracing to have correct
handling of parallel rays and discard any self intersection with normal
screen raytrace.
---
 .../draw/engines/eevee/shaders/raytrace_lib.glsl   | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

(limited to 'source/blender/draw/engines')

diff --git a/source/blender/draw/engines/eevee/shaders/raytrace_lib.glsl b/source/blender/draw/engines/eevee/shaders/raytrace_lib.glsl
index 5ea7e502a55..5c4fe6d47a0 100644
--- a/source/blender/draw/engines/eevee/shaders/raytrace_lib.glsl
+++ b/source/blender/draw/engines/eevee/shaders/raytrace_lib.glsl
@@ -12,6 +12,7 @@ uniform sampler2DArray planarDepth;
 
 struct Ray {
   vec3 origin;
+  /* Ray direction premultiplied by its maximum length. */
   vec3 direction;
 };
 
@@ -46,12 +47,7 @@ void raytrace_screenspace_ray_finalize(inout ScreenSpaceRay ray)
   /* If the line is degenerate, make it cover at least one pixel
    * to not have to handle zero-pixel extent as a special case later */
   if (len_squared(ray.direction.xy) < 0.00001) {
-    ray.direction.xy = vec2(0.0, 0.01);
-  }
-  /* Avoid divide by 0 error in line_unit_box_intersect_dist, leading to undefined behavior
-   * (see T86429). */
-  if (ray.direction.z == 0.0) {
-    ray.direction.z = 0.0001;
+    ray.direction.xy = vec2(0.0, 0.00001);
   }
   float ray_len_sqr = len_squared(ray.direction.xyz);
   /* Make ray.direction cover one pixel. */
@@ -61,7 +57,7 @@ void raytrace_screenspace_ray_finalize(inout ScreenSpaceRay ray)
   /* Clip to segment's end. */
   ray.max_time = sqrt(ray_len_sqr * safe_rcp(len_squared(ray.direction.xyz)));
   /* Clipping to frustum sides. */
-  float clip_dist = line_unit_box_intersect_dist(ray.origin.xyz, ray.direction.xyz);
+  float clip_dist = line_unit_box_intersect_dist_safe(ray.origin.xyz, ray.direction.xyz);
   ray.max_time = min(ray.max_time, clip_dist);
   /* Convert to texture coords [0..1] range. */
   ray.origin = ray.origin * 0.5 + 0.5;
@@ -104,8 +100,7 @@ struct RayTraceParameters {
   float roughness;
 };
 
-/* Return true on hit. */
-/* __ray_dir__ is the ray direction premultiplied by its maximum length */
+/* Returns true on hit. */
 /* TODO fclem remove the backface check and do it the SSR resolve code. */
 bool raytrace(Ray ray,
               RayTraceParameters params,
@@ -119,7 +114,10 @@ bool raytrace(Ray ray,
 
   ScreenSpaceRay ssray = raytrace_screenspace_ray_create(ray, params.thickness);
   /* Avoid no iteration. */
-  ssray.max_time = max(ssray.max_time, 1.1);
+  if (ssray.max_time < 1.1) {
+    hit_position = ssray.origin.xyz + ssray.direction.xyz;
+    return false;
+  }
 
   float prev_delta = 0.0, prev_time = 0.0;
   float depth_sample = get_depth_from_view_z(ray.origin.z);
@@ -177,13 +175,13 @@ bool raytrace_planar(Ray ray, RayTraceParameters params, int planar_ref_id, out
   ssray.direction.x = -ssray.direction.x;
 
   float prev_delta = 0.0, prev_time = 0.0;
-  float depth_sample = get_depth_from_view_z(ray.origin.z);
+  float depth_sample = texture(planarDepth, vec3(ssray.origin.xy, planar_ref_id)).r;
   float delta = depth_sample - ssray.origin.z;
 
   float t = 0.0, time = 0.0;
   /* On very sharp reflections, the ray can be perfectly aligned with the view direction
    * making the tracing useless. Bypass tracing in this case. */
-  bool hit = (ssray.max_time < 1.0);
+  bool hit = false;
   const float max_steps = 255.0;
   for (float iter = 1.0; !hit && (time < ssray.max_time) && (iter < max_steps); iter++) {
     float stride = 1.0 + iter * params.trace_quality;
-- 
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